{"paper_id":"4abb7110-59cd-4437-b380-5efd5aafab79","body_text":"Synergistic Bimetallic Catalysis for Closed-Loop Polyurethane Foam Upcycling via Proximity-Driven Depolymerization | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Synergistic Bimetallic Catalysis for Closed-Loop Polyurethane Foam Upcycling via Proximity-Driven Depolymerization Huiwen He, Du kaiming, Zongsheng Liu, Fan Yang, Ming Lu, Hang Hu, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6709291/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract The development of efficient catalytic systems for polyurethane foam (PUF) recycling under mild conditions remains a critical challenge in achieving sustainable plastic circularity. Here, we report a ternary catalyst (TMG/Cd/HMMI) featuring a bimetallic Cd(II) center coordinated with 1,1,3,3-tetramethylguanidine (TMG) and 1-methyl-2-hydroxymethylimidazole (HMMI), which synergistically enhances the depolymerization of PUF. Integrated with a multi-stage degradation strategy, the catalyst efficiently catalyzes the degradation of carbamate and urea bonds in PUF under mild conditions (180 – 200 °C, 4 h, 10 wt% degradation agent relative to PUF mass), enabling spontaneous phase separation into high-purity recycled polyols (RP) and isocyanate-derived hard segments (HS) without requiring purification. The RP exhibit near-identical properties to virgin polyols and can substitute up to 40 wt% in new foam synthesis without compromising mechanical performance. Meanwhile, the hard segment can be reused as a reinforcing additive of rigid foam. This approach ensures full resource recovery, aligning with circular economy principles. Physical sciences/Chemistry/Green chemistry/Sustainability Scientific community and society/Business and industry/Engineering/Chemical engineering Physical sciences/Chemistry/Catalysis/Catalytic mechanisms Physical sciences/Chemistry/Polymer chemistry/Polymer synthesis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The escalating accumulation of plastic waste poses a dire threat to global ecosystems 1 – 6 , with polyurethane (PU) a versatile polymer integral to foams, elastomers, and coatings—representing 8% of annual plastic production. According to projections from a report published by Grand View Research, the global polyurethane market size is estimated to reach approximately $ 88 billion by 2025 (corresponding to a consumption volume of around 25–28 million metric tons). Conventional disposal methods, such as incineration and landfilling, exacerbate environmental degradation while squandering valuable resources 4 , 7 , 8 . Although physical recycling offers partial mitigation, it often compromises material performance. Chemical recycling, which depolymerizes PU into reusable monomers, holds promise but remains hindered by harsh chemical conditions (> 210°C, 6–12 h reaction time), excessive degradation agent consumption (agent to PUF mass ratios of 1:1 to 4:4), and hazardous byproducts (e.g., uncontrolled pyrolysis products from thermal degradation). 9 , 10 . Therefore, there is an urgent need to design efficient and safe catalytic degradation systems to develop more effective and environmentally friendly recycling pathways that can achieve higher degrees of PU depolymerization under mild or even more favorable conditions. Polyurethane foam (PUF), constituting over 50% of global PU consumption, poses formidable challenges for chemical recycling due to its three-dimensional cross-linked network architecture. In recent years, extensive research has been conducted on the degradation of PUF using amine-based catalysts, nitrogen-containing heterocyclic catalysts, and metal catalysts 11 , 12 . Key factors in catalyst design include enhancing the nucleophilicity of the degradation agents and increasing the electrophilicity of the carbamate bonds 10 , 13 – 15 . Meanwhile, since PUF are three-dimensional cross-linked thermosetting polymers, the issue of reaction collision probability must be considered from a practical application perspective 16 – 20 . Additionally, the presence of metal elements can significantly influence the reaction between polyols and isocyanates during PUF synthesis, necessitating careful consideration of metal residue. These two aspects are often overlooked in current research. Enzyme-mediated depolymerization under mild conditions holds significant promise for sustainable plastic recycling and environmental remediation. A key mechanistic advantage of enzymatic systems lies in their proximity effect—a phenomenon where substrate-binding clefts spatially confine reactive groups (e.g., carbonyl and hydroxyl moieties), effectively mimicking elevated local reactant concentrations to lower activation barriers. This strategy, widely employed by natural hydrolytic enzymes (e.g., cutinases, lipases), has inspired biomimetic approaches for synthetic polymer degradation. A prevailing strategy involves constructing structural analogs or functional mimics of hydrolytic enzyme active sites 21 – 25 . Zhang et al 22 . biomimetic designs leveraging binuclear metallohydrolases, achieving efficient polyethylene terephthalate (PET) degradation. Inspired by these mechanistic parallels, we explored the feasibility of adapting analogous synergistic strategies—particularly proximity-driven dinuclear catalysis—to the alcoholysis/aminolysis of PUF. In this work (Fig. 1 ), a ternary catalyst featuring a bimetallic Cd (di-Cd²⁺) catalytic center was synthesized by coordinating with 1,1,3,3-tetramethylguanidine (TMG) and 1-methyl-2-hydroxymethylimidazole (HMMI), demonstrating synergistic catalytic effects. In this system, the carbamate bond and the degradation agent are bound to the metal center, bringing the reactants into closer proximity and effectively converting intermolecular reactions into intramolecular reactions, thereby increasing the likelihood of collisions. TMG’s strong basicity activates degradation agents and stabilizes intermediates, while HMMI modulates electron density at the metal center and enhances solubility via its terminal hydroxyl group. The distinct catalytic mechanisms of these three components simultaneously increase the nucleophilicity of the degradation agent and the electrophilicity of the carbamate bond. By integrating the catalyst with a multi-stage degradation strategy, we achieved complete cleavage of carbamate and urea bonds in polyurethane foam (PUF) under mild conditions (180–200°C, 4 h, 10 wt% degradation agent relative to PUF mass), enabling spontaneous phase separation into high-purity recycled polyols (RP) and isocyanate-derived hard segments (HS) without requiring purification. The RP exhibit near-identical properties to virgin polyols (hydroxyl value: 66 mgKOH g⁻¹; viscosity: 950 mPa·s) and can replace 40 wt% of virgin feedstock in new foam synthesis without sacrificing mechanical integrity. At the same time, the hard segments are repurposed as reinforcing additives for rigid foams, improving the mechanical properties. This closed-loop strategy eliminates purification steps, minimizes waste, and aligns with circular economy principles. By bridging enzymatic mimicry with metal coordination chemistry, our work redefines catalytic PUF recycling, offering a scalable pathway to mitigate plastic pollution while reclaiming value from waste. Results and discussion Characterization of catalyst The ternary catalyst TMG/Cd/HMMI was synthesized by reacting 1,1,3,3-tetramethylguanidine (TMG), 1-methyl-2-hydroxymethylimidazole (HMMI), and cadmium nitrate in acetone at 60°C for 4 hours ( Extended Data Fig. 1 a; full protocols in the section ‘Materials and general measurements’ in Methods). To confirm the complex formation and stoichiometry, the raw materials and final product were analyzed via 1 H NMR spectroscopy ( Extended Data Fig. 1 b). Compared to free HMMI, the proton signals of HMMI in the complex exhibited downfield shifts, attributed to electron density loss upon coordination. Integration of key proton environments (H1 from TMG and H2 from HMMI) revealed a 4:1 ratio ( Extended Data Fig. 1 c), confirming a 1:1 molar ratio of TMG to HMMI in the catalyst. The successful synthesis of the TMG/Cd/HMMI complex was further confirmed through spectroscopic and thermal analyses. UV-Vis spectroscopy revealed a distinct blue shift in the absorption band of HMMI after coordination (Fig. 2 a), indicating electronic interaction between the ligand and Cd(II) center. X-ray photoelectron spectroscopy (XPS) analysis demonstrated a 1.32 eV reduction in the Cd 3d₅/₂ binding energy (405.08 eV for TMG/Cd/HMMI vs. 406.4 eV for cadmium nitrate; Fig. 2 b, Table S1 26 ), attributed to increased electron density around cadmium ions upon ligand coordination. Further analysis of the N 1s spectrum resolved four distinct nitrogen environments (401.06, 400.40, 399.23, and 398.57 eV; Fig. 2 c), corresponding to coordinated nitrogen atoms from TMG and HMMI. Elemental analysis via organic elemental analysis (OEA, Table S2 ), inductively coupled plasma-mass spectrometry (ICP-MS, Table S2 ), and thermogravimetric analysis (TGA, Fig. 2 d) confirmed the catalyst composition. ICP-MS and TGA revealed mutually corroborating cadmium contents of 36.19% ( Table S2 ) and 37.27% ( Table S3 ), respectively. TGA further demonstrated enhanced thermal stability of the complex after ligand coordination, with no decomposition observed within the degradation temperature range (160–200°C). Energy-dispersive X-ray spectroscopy (EDS) line scans verified the homogeneous distribution of N, O, and Cd throughout the catalyst structure (Fig. 2 e-f). The atomic structure of TMG/Cd/HMMI was further analyzed using X-ray absorption fine structure (XAFS) spectroscopy. X-ray absorption near-edge structure (XANES) analysis revealed a distinct red shift in the Cd K-edge absorption energy of TMG/Cd/HMMI compared to CdO and CdS (Fig. 2 a), suggesting the oxidation state of the Cd atoms in TMG/Cd/HMMI was below + 2. EXAFS fitting (Fig. 2 j) further confirmed the presence of direct Cd–Cd interactions (coordination number: 1.2; bond length: 2.39 Å), alongside Cd–O/N coordination (coordination number: 4.3; bond length: 2.27 Å, Table S4 ). These findings unambiguously establish TMG/Cd/HMMI as a dinuclear complex with a Cd–Cd metallic bond. The shortened Cd–Cd distance (relative to Cd-foil, 2.94 Å 27 ) suggests significant electron delocalization between the two Cd centers, likely contributing to the system’s exceptional catalytic activity through cooperative bond activation. Investigation of catalytic effect and mechanism of TMG/Cd/HMMI Polyurethane foam (PUF), a three-dimensional cross-linked network synthesized from diisocyanates and polyols using water as a blowing agent and amine/tin catalysts, contains diverse functional groups (e.g., carbamate, urea, ether linkages) that complicate degradation mechanism studies. To address this, we designed two small-molecule models—structurally analogous to PUF—to specifically mimic carbamate (diethyl (4-methyl-1,3-phenylene) dicarbamate, DMPC) and urea (N,N-diphenyl urea, DPU) linkages, enabling systematic investigation of degradation and catalytic pathways. (The details of synthesis and characterization are in the ‘Model Compound Experiment’ section of the Methods.) The catalytic performance and mechanism of TMG/Cd/HMMI were systematically investigated using DMPC and DPU as model substrates under mild conditions (Detailed degradation formulations and procedures are provided in the section ‘Model compound experiments’ in Methods. Kinetic calculations were reported in our prior publication 20 ). Kinetic analysis revealed a biphasic degradation process for DPU (Fig. 3 a), with activation energies of 97.6 ± 11.2 kJ mol⁻¹ (step 1) and 139.0 ± 14.3 kJ mol⁻¹ (step 2), reflecting distinct energy barriers for sequential bond cleavage (Fig. 3 a). Similarly, DMPC degradation proceeded stepwise: ethanol release (Fig. 3 b, step 1) preceded toluene-2,4-diamine (TDA) formation (Fig. 3 b, step 2). TMG/Cd/HMMI outperformed its individual components (Cd(NO₃)₂, TMG, HMMI; Fig. 3 c–e), enhancing aniline yields by 25% (vs. Cd(NO₃)₂), 72% (vs. TMG), and 107% (vs. HMMI) for DPU at 60 min, and boosting TDA production by 249%, 780%, and 659% for DMPC at 180 min, respectively. Comparative studies with conventional catalysts further demonstrated TMG/Cd/HMMI’s superior activity in both DPU dissociation and TDA formation (Fig. 3 f–h). Based on the above discussion, the influence of metal ions on catalytic efficiency is particularly pronounced. Therefore, we synthesized dual-ligand metal complexes using the same ligands but incorporating different metal ions. Comparative studies of dual-ligand metal complexes with identical ligands but varying metal centers revealed Cd(II)’s exceptional catalytic performance in cleaving both carbamate (DMPC) and urea (DPU) bonds, with activity hierarchies of Cd(II) > Co(II) > Cu(II) > Ni(II) > Zn(II) for DMPC (Fig. 4 a, 4 d-e) and Cd(II) > Ni(II) > Zn(II) > Co(II) > Cu(II) for DPU (Fig. 4 b, 4 c). This remarkable advantage of Cd(II) may come from its unique structure and electronic properties. The relatively large ionic radius of Cd(II) (0.95 Å) enhances coordination flexibility, enabling diverse geometries that accommodate multiple ligands while providing spatial freedom for carbonyl group activation and reactant positioning near catalytic sites. This structural adaptability facilitates rapid product release and efficient polarization of the carbonyl moiety during reactions. Complementing this, Cd(II)’s closed-shell [Kr]4d¹⁰ electronic configuration minimizes π-backbonding and orbital hybridization, allowing the metal to prioritize strong σ-coordination with ligands. This focused electronic interaction stabilizes the catalytic complex and enhances its ability to sustain electron withdrawal from the carbonyl group, thereby lowering activation barriers. To elucidate ligand roles in the TMG/Cd/HMMI system, we decoupled the ternary complex into pairwise combinations (TMG/Cd, Cd/HMMI, TMG/HMMI) and assessed their catalytic efficiencies via the second-stage DMPC degradation (TDA formation). TMG/Cd coordination proved pivotal, enhancing TDA yields by 623% (vs. TMG) and 190% (vs. Cd(NO₃)₂) at 180 min ( Extended Data Fig. 2 a), attributed to TMG’s strong basicity enabling degradation agent (diethanolamine, DEA) deprotonation. Screening cadmium salts with varying anion basicities (OH⁻ > CH₃COO⁻ > NO₃⁻) confirmed ligand basicity-activity correlations (TMG/Cd > Cd(OH)₂ > Cd(OAc)₂ > Cd(NO₃)₂; Extended Data Fig. 2 b). ICP-MS revealed exceptional Cd loading (80.38 wt%, Table S5 ) in TMG/Cd, suggesting the formation of Cd-Cd metallic bonds that may amplify electron delocalization at active sites. Introducing HMMI reduced Cd content to 36.33 wt% but paradoxically increased catalytic efficiency by 21% (vs. TMG/Cd) and 197% (vs. Cd/HMMI), owing to its dual roles: (1) imidazole-mediated electron transfer lowering transition-state barriers, and (2) HMMI can promote the complete dissolution of catalyst in DEA within 10 minutes at 160°C (vs. 9.26% for TMG/Cd; Table S6 ). These findings establish a synergistic paradigm: TMG optimizes bond activation via basicity, while HMMI regulates electron transport and solubility, overcoming limitations of single-ligand systems. Degradation of carbamate oligomer Since the previous discussions were based on the small molecule models DMPC (carbamate bond) and DPU (urea bond), which differ significantly from polymers in terms of primary, secondary, and tertiary structures, we synthesized a linear carbamate oligomer (CbO, Mₙ = 3,147 Da) to further investigate and validate the degradation mechanism and catalytic behavior ( Fig. S2 ). The synthesis procedure and basic data for CbO can be found in the section ‘Model compound experiments’ in Methods. First, we explored the degradation mechanism of CbO, with detailed experimental procedures outlined in the section ‘Model compound experiments’ in Methods. Degradation of CbO in the presence of TMG/Cd/HMMI unveiled a two-step mechanism (Fig. 5 e): initial nucleophilic attack by DEA at carbamate bonds releases diethylene glycol (DEG, Fig. 5 c), followed by hydroxyl-terminated intermediate cyclization to yield 4,4'-methylenedianiline (MDA, Fig. 5 d) and 3-(2-hydroxyethyl)oxazolidin-2-one (MDA, Fig. 5 b). This pathway, corroborated by GC-MS identification of all intermediates (Fig. 5 a-d), confirming consistency with the stepwise degradation observed in the small-molecule DMPC model, and verified the rationality of the small molecule model as a prediction tool for polymer degradation. To quantify catalytic efficiency in polymeric contexts, we monitored DEG and MDA production kinetics under catalytic and non-catalytic conditions. As demonstrated in Fig. 5 f, in the presence of TMG/Cd/HMMI, the degradation of CbO is higher than that of non-catalytic system by > 433% within 150 minutes. This further confirms the effectiveness of the the catalyst maintained stability without deactivation, even in the presence of long-chain polymer segments. The catalytic mechanism was investigated by monitoring the reaction process through infrared (FTIR) spectroscopy. The results are shown in Extended Data Fig. 3 a. In the IR spectrum, the N-H stretching vibration, typically appearing between 3300–3500 cm⁻¹ and primarily originating from the amino groups in both carbamate bonds and DEA, exhibited a blue shift from 3281 cm⁻¹ to 3308 cm⁻¹ upon the introduction of TMG/Cd/HMMI. This shift indicates that the addition of the catalyst disrupts the original hydrogen-bond network, allowing the N-H bonds to vibrate more freely, thereby increasing the vibrational frequency. Simultaneously, the electron cloud density around the amino groups in DEA is enhanced, which increases their reactivity. A similar blue shift was observed in the N-H bending vibration, which shifted from 1594 cm⁻¹ to 1607 cm⁻¹ following the addition of TMG/Cd/HMMI. Moreover, the ester bond stretching vibration peak also shifted from 1707 cm⁻¹ to 1725 cm⁻¹, suggesting that the coordination of TMG/Cd/HMMI with the carbonyl oxygen induces electron transfer towards the oxygen atom, enhancing the positive charge on the carbonyl carbon, thereby making it more prone to nucleophilic attack by DEA. Building on these observations, the catalytic mechanism can be proposed as follows ( Extended Data Fig. 3 b, 3 c): The dinuclear Cd(II) center orchestrates both proximity control and electronic activation. First, it spatially confines DEA’s amine groups and carbamate carbonyl oxygen through simultaneous coordination, effectively converting intermolecular reactions into pseudo-intramolecular processes with elevated local substrate concentrations. Second, Cd(II)’s strong electron-withdrawing capacity polarizes the carbonyl group, lowering the activation barrier for nucleophilic cleavage. This bifunctional action is synergistically amplified by HMMI’s electron-transfer mediation and TMG’s basicity, which respectively optimize charge transfer kinetics and substrate deprotonation. Degradation of Waste Polyurethane Foam (PUF) DEA Degradation System (Catalytic Effect Verification) Based on the previously established catalytic mechanism, we applied the TMG/Cd/HMMI catalytic degradation system to the degradation of waste polyurethane foam (PUF). The degradation of PUF was evaluated under mild conditions (180°C, using DEA as the degrading agent), with detailed degradation formulations and procedures provided in the section ‘Degradation of Waste Polyurethane Foam (PUF)’ in Methods. In the presence of TMG/Cd/HMMI, the system achieved complete liquefaction within 39 minutes, followed by spontaneous phase separation into a low-viscosity recycled polyol phase (RP, 950 mPa·s) and an isocyanate-derived hard segment (HS) ( Fig. S3 ), which is remarkable given that the amount of DEA used was only 10 wt% of the PUF. In contrast, traditional catalysts (e.g., Zn(OAc)₂, TMEDA, DMCHA), under the same conditions, failed to obtain low viscosity RP ( Fig. S4 , Table 1 ). An analysis of the small molecule dissociation results provides insights into the phase separation mechanism observed during PUF degradation in the TMG/Cd/HMMI system. In most other catalytic degradation systems, only partial C-O bonds and a very limited number of C-N bonds (isocyanate segments) are cleaved, leaving the isocyanate segments attached to the polyol chain. These isocyanate fragments, typically associated with short chains containing aromatic structures, increase the viscosity of the system. However, the TMG/Cd/HMMI system can effectively activates DEA, promoting its attack on both carbamate and urea bonds. This leads to complete cleavage of C–N bonds, fully liberating the isocyanate segments from the polyol backbone. Furthermore, due to the partial compatibility between the isocyanate segments and the polyol phase, spontaneous phase separation occurs upon standing without requiring any additional processing. Although TMG/Cd/HMMI exhibits high catalytic efficiency, the potential toxicity of Cd(II) necessitates careful examination of its distribution in degradation products. ICP-MS analysis of both the recycled polyol (RP) and hard segment (HS) revealed negligible Cd(II) residues in the RP (8 ppm, Table S7 )—well below the heavy metal content limits for the flexible foam furniture industry. This confirms the RP’s practical applicability while ensuring compliance with environmental and safety standards. Table 1 Degradation of PUF under Different Catalysts. entry degradation agent catalyst time a (min) RP viscosity (mPa·s) 1 DEA / 90–120 12700 2 DEA TMG 40 13600 3 DEA MMI 60 5560 4 DEA Zn(OAC) 2 70 3050 5 DEA DMCHA 70 3870 6 DEA TMEDA 90 3100 7 DEA PMDETA 70 6570 8 DEA TMG/Cd/HMMI 39 950 a: Time required to put in 100g foam. Multistage Degradation System (Practical application of catalyst) To further evaluate the practical application potential of TMG/Cd/HMMI, we integrated it into the multi-stage degradation system. The operational principles and mechanistic insights of this multi-stage degradation system have been detailed in our previous work 20 (See in the section ' Degradation of Waste Polyurethane Foam (PUF)’ in Methods for specific degradation formulations and procedures). Characterization of the RP ( Table S8 ) confirmed complete cleavage of polyol-isocyanate linkages, enabling spontaneous phase separation into RP and isocyanate-derived hard segments (HS). The hydroxyl value (HV) of RP-TMG/Cd/HMMI slightly exceeded that of virgin polyol (VP), which is attributed to trace residual DEA. Since DEA inherently acts as a catalyst in polyurethane foaming, no further purification is required—only an adjustment of amine catalyst dosage during re-foaming is necessary. Subsequently, RP-TMG/Cd/HMMI was employed to partially replace VP (0–40 wt%) in synthesizing flexible polyurethane foams (Foaming formulations and protocols are provided in the section ‘Re-foaming experiment of recycled polyol’ in Methods). Digital photos and SEM images of flexible regenerated polyurethane foam (Flexible - RPUF) with varying RP contents ( Fig. S5 ) revealed preserved structural integrity in RPUF-40RP, exhibiting well-defined cellular architecture with only marginal yellowing. As shown in Extended Data Fig. 4 a, Table S10 the mechanical properties of Flexible - RPUF with 40 wt% RP substitution remained compliant with commercial standards. The isocyanate-derived hard segments generated during depolymerization comprising amide derivatives with residual polyol fragments exhibit dual functionality: partial compatibility with virgin polyols and inherent structural rigidity. Capitalizing on these traits, HS were repurposed as reinforcing fillers for rigid polyurethane foams, analogous to calcium carbonate additives. Pre-crushed HS were blended with PPG via ball milling prior to foaming. Detailed protocols in the section ‘Re-foaming experiment of recycled polyol’ in Methods. Incorporation of HS increased polyol viscosity and caused mild discoloration in both recycled polyols and foams ( Fig. S6, Table S9 ). At 40 wt% loading, rigid regenerated polyurethane foam (Rigid - RPUF) exhibited significant enhancements ( Extended Data Fig. 4 b, Table S11 ): 27.15% higher density, 34.53% greater hardness, and 202.88% improved 10% compressive strength versus HS-free counterparts. This strategy not only eliminates HS waste but also aligns with circular economy principles by transforming byproducts into value-added materials. Calculation of environmental energy impact A rigorous sustainability assessment was conducted to benchmark the TMG/Cd/HMMI system against conventional catalytic approaches using the tripartite green chemistry metrics proposed by Thelemans et al. and Zhang et al. 28 , 29 : energy economy (ε), environmental factor (E), and environmental-energy impact (ξ) (See in the section ‘Calculation of environmental energy impact’ in Methods for calculation method). Ideal depolymerization processes are characterized by maximized ε alongside minimized E and ξ. As quantified in Tables S12, S13 , TMG/Cd/HMMI outperforms traditional catalysts, achieving exceptional ε values of 2.95×10⁻³ and 9.72×10⁻³ o C −1 ·min − 1 for carbamate and urea bond cleavage, respectively. Concurrently, it maintains ultralow environmental impact (E: 3.05 and 0.34; ξ: 1.04×10³ and 35.06 o C·min). This dual optimization of energy efficiency and environmental compatibility underscores the system’s unique potential for scalable polyurethane upcycling. Conclusions The relentless accumulation of PUF waste demands catalytic technologies that balance efficiency, sustainability, and practicality. In this study, we address this challenge through the rational design of TMG/Cd/HMMI, a ternary catalyst that leverages the complementary roles of TMG (basicity), HMMI (electron transfer, compatibility), and Cd(II) (electrophilic activation) to depolymerize PUF under mild conditions. By coordinating Cd(II) with TMG and HMMI, we create a dinuclear catalytic center that accelerates bond cleavage via a proximity effect, effectively converting intermolecular reactions into intramolecular processes. This mechanism ensures complete degradation of PUF under mild conditions (180–200°C, 4 h, 10% degradation agent relative to PUF mass) into phase-separated RP and hard segments. The RP retain commercial-grade properties (e.g., hydroxyl value: 66 mgKOH g⁻¹, viscosity: 950 mPa·s) and directly replace virgin polyols in foam production, while the hard segment can enhance the strength of rigid foam by mixing with polyol. This work not only advances catalytic PUF recycling but also redefines waste valorization by transforming \"non-recyclable\" hard segments into reinforcing fillers. Our findings illuminate a pathway toward industrial-scale plastic upcycling, where catalytic design aligns with circular economy principles to reconcile ecological and economic imperatives. Methods Materials and general measurements Materials. During the catalyst synthesis, cadmium nitrate (Cd(NO₃)₂·H₂O), 1,1,3,3-tetramethylguanidine (TMG), and 1-methyl-2-hydroxymethylimidazole (HMMI) (all supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) were used. PUFs waste (supplied by Sinomax (Zhejiang) Polyurethane Technology Limited.) uses diethanolamine (supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) and succinic acid (supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) as degradation agents for multi-stage degradation. In the synthesis of model molecules, anhydrous ethanol, diethylene glycol, and methylene diphenyl diisocyanate (MDI) (all supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) were employed. The model molecule 1,3-diphenylurea (DPU) was supplied by Shanghai Aladdin Biochemical Technology Co., Ltd. For regenerated foam production, traditional petroleum-based polyol (PPG5623, supplied by Zhejiang Hengfeng New Material Co., Ltd.), JB-635C polyol (supplied by Jiangsu Zhongshan Chemical Co., Ltd.), 2,4-toluene diisocyanate (TDI), polymeric methylene diphenyl diisocyanate (PAPI) (supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.), silicone surfactant (silicone oil, supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.), foaming agent (distilled water), and catalysts (triethylamine, dibutyltin dilaurate, and stannous octoate, supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) were utilized. Synthesis of TMG/Cd/HMMI. Cd(NO₃)₂·H₂O (86.9 mmol), TMG (86.9 mmol), HMMI (86.9 mmol), and 50 mL acetone were added to a 250 mL three-neck flask, and the mixture was reacted at 60 °C for 4 hours ( Extended Data Fig. 1 ). After the reaction, the product was filtered and washed with deionized water. Finally, the product was dried in a vacuum oven at 80°C for 48 hours, then ground to obtain TMG/Cd/HMMI with an 80% yield. General measurements. 1 H NMR spectra were recorded using a Bruker AVANCE NEO 400 MHz instrument (Bruker Corporation, USA) at room temperature in DMSO- d 6 . Chemical shifts are given in ppm relative to a DMSO- d 6 residual peak. The change of integral area of proton peak of DMPC and DPU with reaction time was monitored to evaluate the catalytic effect under different catalysts. The transparency of TMG/Cd/HMMI were measured by UV-vis spectrophotometer (PerkinElmer, Lambda750s, USA). X-ray photoelectron spectroscopy ( XPS , Esca Lab 250X, Thermo Fisher, USA) is used to analyze the changes of binding energy of elements in TMG/Cd/HMMI. Thermogravimetric analyzer ( TG , 209 F1, Netzsch Germany) is used to test the thermal stability of CbO and TMG/Cd/HMMI. The thermal stability of the sample was analyzed at the rate of 10 o C /min from room temperature to 600 o C in air or nitrogen. Differential scanning calorimetry ( DSC ) is used to test the thermal behavior of CbO in nitrogen atmosphere. The samples were drop coated on amorphous carbon-coated Cu grids. TEM images were recorded by using a JEM-1010 microscope at an accelerating voltage of 80 kV. Data reduction, data analysis, and EXAFS fitting were performed and analyzed with the Athena and Artemis programs of the Demeter data analysis packages 30 that utilizes the FEFF6 program 31 to fit the EXAFS data. The energy was calibrated using the correspond metal foil, which as a reference was simultaneously measured. A linear function was subtracted from the pre-edge region, then the edge jump was normalized using Athena software. The χ(k) data were isolated by subtracting a smooth, third-order polynomial approximating the absorption background of an isolated atom. The k 3 -weighted χ(k) data were Fourier transformed after applying a Hanning window function (Δk = 1.0). For EXAFS modeling, the global amplitude EXAFS (CN, R, σ 2 and ΔE 0 ) were obtained by nonlinear fitting, with least-squares refinement, of the EXAFS equation to the Fourier-transformed data in R-space, using Artemis software. For Wavelet Transform analysis, the χ(k) exported from Athena was imported into the Hama Fortran code. The parameters were listed as follow: R range, 0 – 6 Å, k range, 0 - 12.0 Å-1; k weight, 3; and Morlet function with κ=10, σ=1 was used as the mother wavelet to provide the overall distribution 32 . The FT-IR spectra of RP were measured on a Nicolet 6700 Fourier Transform Infrared Spectrometer of Thermo Fisher Company (America) in the wave number range of 650 to 4000 cm -1 . The microstructures test was observed by scanning electron microscopy ( SEM , JEOL JSM-5900LV, Japan) at 10 kV acceleration voltage. Organic element analysis ( OEA , Thermo Fisher) was used to measure the element content of TMG/Cd/HMMI. Inductively coupled plasma-Mass Spectrometry ( ICP-MS , Thermo Fisher) was used to measure the metal content of catalyst. The molecular weight and dispersity (Ð) of RP were determined by gel permeation chromatography (PL- GPC 50, Aligent, USA), using THF as solvent and polystyrene as standard sample. The instrument model is GCMS -QP2010 Plus (chromatographic columnmodel: DB-17MS; chromatographic column size: 60 m × 250 μm × 0.25 μm). Model compound experiments Synthesis of Diethyl (4-Methyl-1,3-Phenylene) Dicarbamate (DMPC) as a Model Compound. 250 g (5.43 mol) of anhydrous ethanol was weighed into a 500 mL round-bottom flask, and under magnetic stirring and an ice-water bath, 80 g (0.46 mol) of tolylene-2,4-diisocyanate (TDI) was added dropwise to the flask. The reaction temperature was maintained at 0°C and continued for 2 hours. The resulting reaction mixture was concentrated under reduced pressure at 55°C using a rotary evaporator to remove excess ethanol, then transferred to a vacuum oven at 70°C and dried for 48 hours, yielding a white powder, DMPC, with a 93% yield. The 1 H NMR characterization in DMSO- d 6 is shown in Fig. S1 , confirming the product as diethyl (4-methyl-1,3-phenylene) dicarbamate (DMPC). Synthesis of carbamate oligomer (CbO). 30 g (282.7 mmol) of diethylene glycol (DEG) was weighed into a 500 mL beaker. At room temperature and under high-speed stirring, 47.16 g (188.5 mmol) of methylene diphenyl diisocyanate (MDI) was rapidly added. After stirring at high speed for 30 s, the mixture was transferred to an oven at 60°C for 24 h to cure. The cured product was then dissolved in THF and reprecipitated using ethanol as a poor solvent. The resulting precipitate was dried in a vacuum oven at 60°C for 48 h to yield a white powder designated as carbamate oligomer (CbO), with a yield of 95%. Gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were performed on CbO ( Fig. S2 ). The results indicated that CbO has a weight-average molecular weight of 5597 and a thermal decomposition temperature of 300 °C, ensuring that CbO will not undergo thermal degradation at the experimental degradation temperature (160 °C). Degradation of DMPC. DMPC, DEA, and the catalyst were added to a three-neck flask in a molar ratio of 1:5:0.1 and equipped with a reflux condenser. The degradation was carried out at 160°C. Samples were taken at different reaction times, and the reaction was quantitatively monitored by 1H NMR. Degradation of DPU. DPU, DEA, and the catalyst were added to a three-neck flask in a molar ratio of 1:2.5:0.1 and equipped with a reflux condenser. The degradation was performed at 160°C. Samples were taken at different reaction times, and the reaction was quantitatively monitored by 1H NMR. Degradation of Carbamate Oligomer. 10 g of CbO, 8.85 g (84.2 mmol) of DEA, and 2.84 g (5.0 mmol) of TMG/Cd/HMMI were placed in a three-neck flask, and degradation was conducted at 160°C. Samples were taken at various reaction times, and the reaction was quantitatively monitored by GC-MS. The reaction mechanism was studied using Fourier-transform infrared (FTIR) spectroscopy. Degradation of Waste Polyurethane Foam (PUF) DEA Degradation System (Catalytic Effect Verification). 10 g (95.1 mmol) of DEA, 3.53 g (6.1 mmol) of TMG/Cd/HMMI, and 100 g of PPG were placed in a 500 mL three-neck flask. The flask was placed in an oil bath at 180°C, and 100 g of crushed PUF was continuously added, with mechanical stirring for 2 hours. The time for complete dissolution of the PUF was recorded, and the temperature was then raised to 200°C, continuing mechanical stirring for another 2 hours. After the reaction was completed and the mixture was cooled to room temperature, the recovered polyol (RP) was obtained. Multistage Degradation System. 10 g (95.1 mmol) of DEA, 3.53 g (6.1 mmol) of TMG/Cd/HMMI, and 100 g of PPG were placed in a 500 mL three-neck flask. The flask was placed in an oil bath at 180°C, and 100 g of crushed PUF was continuously added, with mechanical stirring for 2 hours. Then, 20 g (175.4 mmol) of succinic acid (SA) was added, and the temperature was raised to 200°C with mechanical stirring for another 2 hours. After the reaction was completed and the mixture was cooled to room temperature, the recovered polyol (RP) was obtained. Re-foaming experiment of recycled polyol Flexible rigid polyurethane re-foaming. Take X g of recovered polyol (RP), (100-X) g of virgin polyol (VP), 3.2 g of H 2 O, 0.8 g of silicone oil, 0.05 g of triethylamine, 0.2 g of diethanolamine, and 0.14 g of stannous octanoate and place them in a plastic beaker. Use a high-speed stirring plate to stir at 2000 rpm for 20 s until a uniform dispersion is formed; Take 46 g TDI and add it to the dispersion solution. Continue to use the high-speed stirring plate to stir at 2000 rpm for 10 seconds, and then quickly pour the mixture into the mold for molding. After the foaming height no longer changes, move it into an oven at 70 o C and take it out after curing for 22 hours to obtain RPUF-XRP. X represents the replacement amount of RP. Hard segment treatment and rigid polyurethane re-foaming. The procedure involved pre-crushing hard segments to ≤500 μm particles, followed by ball milling 100 g PPG5623 with X g of the crushed segments in a planetary mill (720 rpm, 6–8 h) to produce a homogeneous XHS%/PPG composite. Subsequently, 100 + X g of the XHS%/PPG was combined with 100 g polyether polyol (JB-635C), 4 g triethanolamine, 0.5 g dibutyltin dilaurate, 2 g H₂O, and 4 g silicone oil in a plastic beaker, homogenized at 2000 rpm for 20 s. After adding 108.8 g PAPI under continuous stirring (2000 rpm, 10 s), the mixture was immediately transferred to a mold. After the foaming height no longer changes, move it into an oven at 70 o C and take it out after curing for 22 hours to obtain rigid RPUF-XHS. Characterization methods for polyols Acid value (AV). The acid value (AV) was determined in accordance with the ASTM D4662-08 standard. Approximately 2 g of polyol was dispersed in 50 mL of ethanol in a 100 mL Erlenmeyer flask. Titrations were conducted using 0.1 N NaOH solution and the end point determined using a digital pH meter (HI 2211 pH/ORP−Hanna Instruments), equipped with a HI 1043B probe. The AV was calculated using equation 1. AV=(A−B) ×56.1×N/W (1) where A is the volume of NaOH solution required for the titration of the sample (mL); B is the volume of NaOH solution required for the titration of the blank (mL); N is the normality of the NaOH solution; and W is the weight of the sample (g). Hydroxyl number (HV). The hydroxyl number (HV) was determined in accordance with the ASTM D4274-05 standard in which the esterification process is catalyzed by imidazole. Titrations were conducted using 0.5 N NaOH solution. The HV was corrected taking into account the AV and calculated according to equation 2. HV= ((A− B) ×56.1×N)/W+ AV (2) Where A is the volume of NaOH solution required for the titration of the sample (mL); B is the volume of NaOH solution required for the titration of the blank (mL); N is the normality of the NaOH solution; W is the weight of the sample (g); and AV is the acid value of the sample (mg KOH/g). Viscosity. According to \"GB/T12008.7-2010\" viscosity testing method, the viscosity of polyol was measured with \"NDJ-1B\" rotary viscometer at 25 o C, and the specific operation steps were as follows: Pour a certain amount of recovered polyol sample into a container, put it into a constant temperature water bath at 25 o C and stir. When the sample temperature is 25 o C, select a suitable range of rotary viscometer rotor to immerse in the solution to be measured, and start the rotary viscometer with the standard scale line flush with the liquid level. Record the viscosity of the sample after the indication of the rotary viscometer is stable. Characterization methods for RPUF Density. The density of samples was tested by GB/T 10802-2006. According to GB/T 6342-1996, the length and width of the sample were measured by a tape measure with the minimum division value of 1 mm. Measure the thickness of the sample with a measuring tool with an accuracy of 0.1 mm, and start measuring at a distance of 30 mm from the edge of the sample, with no less than 5 measuring points and even intervals. Rebound rate. The resilience of samples was tested by GB/T 10802-2006. According to GB/T 6670-1997, the sample size is (100± 3) mm× (100± 3) mm× (50± 2) mm, and the number of samples is 3. indentation force deflection. GB/T 10802-2006 was used to test the indentation performance of the samples. According to method B specified in GB/T 10807-2006, the sample size is (380± 20) mm× (380± 20) mm× (50± 2) mm, and the number of samples is three. permanent compression rate. GB/T 10802-2006 was used to test the compression set rate of samples. According to the method A specified in GB/T 6669-2001, the test temperature is 70± 2 ℃, the test time is 22 h, the thickness of the sample is compressed to 25% of the original thickness, and the sample size is (50± 1) mm× (50± 1) mm× (25± 1) mm. Shore C Hardness. The hardness of the sample was tested by Hg/T 2489-1993 standard. According to the method specified in Hg/T 2489-1993, the sample thickness is (10± 5) mm. Compressive properties. The compressive properties of samples were tested by GB/T 8813-2020 standard. According to the method A specified in GB/T 8813-2020, the thickness of the sample is (50± 1)mm, and the compression surface of the sample is (50± 1) mm× (50± 1) mm. Calculation of environmental energy impact To assess the sustainability of comparable methodologies, we employed the tripartite evaluation framework developed by Thielemans et al. and Zhang et al. 28,29 , incorporating energy efficiency metrics (ε), environmental impact factor (E), and combined environmental-energy impact (ξ). A normalized energy economy metric (ε) was introduced to facilitate systematic comparison of process variables including reaction temperature, catalyst selection, and material ratios. This metric is mathematically defined as: where Y represents the mass yield of monomers, T denotes reaction temperature (°C), and t indicates reaction duration (min). The environmental factor (E) was refined from conventional mass intensity calculations to explicitly account for waste generation across material inputs. Finally, the composite parameter ξ integrates both energy and material efficiency through: Ideal catalytic systems are characterized by maximized ε values alongside minimized E and ξ, reflecting optimal energy utilization with minimal ecological burden. Declarations Acknowledgements This work was supported by the Key Research Program of Zhejiang (2021C01087), the National Natural Science Foundation of China (51773180, 52273094, 52003237, 21875009), “Pioneer” R&D Program of Zhejiang (2023C01083) and the Fundamental Research Funds for the Provincial Universities of Zhejiang (2021C01087, 2021C01125), Zhejiang University Students' Science and Technology Innovation Activity Plan (New Miao Talents Plan) (G23131250069). Competing interests The authors declare no competing interests. References Christensen, P. R., Scheuermann, A. M., Loeffler, K. E. & Helms, B. A. Closed-loop recycling of plastics enabled by dynamic covalent diketoenamine bonds. Nature Chemistry 11 , 442-448 (2019). 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H. et al. Chemical upcycling of commodity thermoset polyurethane foams towards high-performance 3D photo-printing resins. Nature Chemistry 15 , 1773-1779 (2023). Villa, R. et al. How to Easily Depolymerize Polyurethane Foam Wastes by Superbase Catalysts in Ionic Liquids Below 100 °C. Angew. Chem.-Int. Edit. 64 , 6 (2025). O'Dea, R. M. et al. Toward Circular Recycling of Polyurethanes: Depolymerization and Recovery of Isocyanates. JACS Au 4 , 1471-1479 (2024). Simón, D., Borreguero, A. M., de Lucas, A. & Rodríguez, J. F. Recycling of polyurethanes from laboratory to industry, a journey towards the sustainability. Waste Manage. 76 , 147-171 (2018). Li, C., Yan, G. M., Dong, Z. W., Zhang, G. & Zhang, F. Upcycling waste commodity polymers into high-performance polyarylate materials with direct utilization of capping agent impurities. Nat. Commun. 16 , 2482 (2025). Suo, H. Y. et al. 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Chemical Recycling of Waste Polyurethane Foams: Efficient Acidolysis under the Catalysis of Zinc Acetate. ACS Sustainable Chemistry & Engineering 11 ,5515-5523 (2023). He, H. W. et al. A new strategy for efficient chemical degradation and recycling of polyurethane materials: a multi-stage degradation method. Green Chemistry 25 , 6405-6415 (2023). Han, X. et al. Structural insight into catalytic mechanism of PET hydrolase. Nat. Commun. 8 , 2106 (2017). Zhang, S. B. et al. Depolymerization of polyesters by a binuclear catalyst for plastic recycling. Nature Sustainability 6 , 965-973 (2023). Pinto, A. V. et al. Reaction Mechanism of MHETase, a PET Degrading Enzyme. ACS Catal. 11 , 10416-10428 (2021). Schenk, G. et al. Binuclear Metallohydrolases: Complex Mechanistic Strategies for a Simple Chemical Reaction. Accounts Chem. Res. 45 , 1593-1603 (2012). Deacy, A. C., Kilpatrick, A. F. R., Regoutz, A. & Williams, C. K. Understanding metal synergy in heterodinuclear catalysts for the copolymerization of CO 2 and epoxides. Nature Chemistry 12 , 372-380 (2020). Tkachenko, O. P., Shpiro, E. S., Wark, M., Schulz-Ekloff, G. & Jaeger, N. I. X-ray photoelectron/X-ray excited auger electron spectroscopic study of highly dispersed semiconductor CdS and CdO species in zeolites. Journal of the Chemical Society, Faraday Transactions 89 , 3987-3994 (1993). Haynes, W.M. (Ed.). CRC Handbook of Chemistry and Physics (97th ed.). (CRC Press, 2016). Barnard, E., Arias, J. J. R. & Thielemans, W. Chemolytic depolymerisation of PET: a review. Green Chemistry 23 , 3765-3789 (2021). Zhang, S. et al. Selective depolymerization of PET to monomers from its waste blends and composites at ambient temperature. Chemical Engineering Journal 470 , 144032 (2023). Ravel, B. & Newville, M. ATHENA, ARTEMIS, HEPHAESTUS : data analysis for X-ray absorption spectroscopy using IFEFFIT . J. Synchrot. Radiat. 12 , 537-541 (2005). Zabinsky, S. I., Rehr, J. J., Ankudinov, A., Albers, R. C. & Eller, M. J. Multiple-scattering calculations of x-ray-absorption spectra. Physical Review B 52 , 2995-3009 (1995). Funke, H., Chukalina, M. & Rossberg, A. Wavelet analysis of extended X-ray absorption fine structure data. Phys. Scr. T115 , 232-234 (2005). Additional Declarations There is NO Competing Interest. Supplementary Files TableofContents.docx SupplementaryInformation.docx Supplementary Information for Synergistic Bimetallic Catalysis for Closed-Loop Polyurethane Foam Upcycling via Proximity-Driven Depolymerization ExtendedDataFigs.docx Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-6709291\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":468594065,\"identity\":\"c472f4a6-f0c2-46e5-b6d3-ef69e65bf9db\",\"order_by\":0,\"name\":\"Huiwen 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1\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":373824,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eSchematic illustration\\u003c/strong\\u003e. (a) The ternary catalyst synthesis. (b) Upcycling pathway for waste polyurethane foam (PUF). (c) The catalytic mechanism.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"1.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/f182eb76d86949ad6c85cbfa.png\"},{\"id\":85381529,\"identity\":\"92b18c70-9279-42e8-9987-ba6d5981a916\",\"added_by\":\"auto\",\"created_at\":\"2025-06-25 09:22:47\",\"extension\":\"png\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":291726,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eStructural characterization of TMG/Cd/HMMI.\\u003c/strong\\u003e (a) Deconvoluted Cd 3d XPS spectra of TMG/Cd/HMMI. (b) Deconvoluted N 1s XPS spectra of TMG/Cd/HMMI. (c) Ultraviolet spectra of HMMI and TMG/Cd/HMMI. (d) TGA and DTG diagrams of TMG, HMMI and TMG/Cd/MMI. (e-h) The elemental distribution of the TMG/Cd/HMMI. (i) XANES spectra at the Cd K-edge of Cd foil, CdO, CdS, TMG/Cd/HMMI catalysts. (j) The corresponding Cd K-edge Extended X-ray Absorption Fine Structure (EXAFS) shown in k\\u003csup\\u003e3\\u003c/sup\\u003e weighted R-space. Fourier-transformed EXAFS \\u003cem\\u003ek\\u003c/em\\u003e\\u003csup\\u003e2\\u003c/sup\\u003e-weighted χ(k) function spectra of the TMG/Cd/HMMI catalysts and references. (k) The Cd K-edge EXAFS and fitting of TMG/Cd/HMMI are shown in k\\u003csup\\u003e3\\u003c/sup\\u003e weighted R-space. (l) The Cd K-edge EXAFS and fitting of TMG/Cd/HMMI are shown in k\\u003csup\\u003e3\\u003c/sup\\u003e weighted k-space.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"2.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/1f5527894a38185ee0dc05ad.png\"},{\"id\":85381531,\"identity\":\"10dbbb8c-2a22-408b-9202-006d2cf05efc\",\"added_by\":\"auto\",\"created_at\":\"2025-06-25 09:22:47\",\"extension\":\"png\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":260855,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eDegradation of different model compounds in DEA system. \\u003c/strong\\u003e(a) Degradation formula of DMPC and activation energy of each step. (b) Degradation formula of DPU and activation energy of each step. (c) The depolymerization rate of \\u003cstrong\\u003etwo-step\\u003c/strong\\u003ereaction of DPU under three kinds of synthetic catalyst raw materials and TMG/Cd/HMMI. (d) The depolymerization rate of the \\u003cstrong\\u003estep 1\\u003c/strong\\u003e reaction of DMPC under three kinds of synthetic catalyst raw materials and TMG/Cd/HMMI. (e) The depolymerization rate of the \\u003cstrong\\u003estep 2 \\u003c/strong\\u003ereaction of DMPC under three kinds of synthetic catalyst raw materials and TMG/Cd/HMMI. (f) The depolymerization rate of \\u003cstrong\\u003etwo-step\\u003c/strong\\u003e reaction of DPU under traditional catalysts and TMG/Cd/HMMI. (g) The depolymerization rate of the \\u003cstrong\\u003estep 1\\u003c/strong\\u003ereaction of DMPC under traditional catalysts and TMG/Cd/HMMI. (h) The depolymerization rate of the \\u003cstrong\\u003estep 2 \\u003c/strong\\u003ereaction of DMPC under traditional catalysts and TMG/Cd/HMMI.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"3.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/183851dc87af85b1a5c9ca05.png\"},{\"id\":85381534,\"identity\":\"c45acd59-ad02-4944-b729-d06aac08e179\",\"added_by\":\"auto\",\"created_at\":\"2025-06-25 09:22:48\",\"extension\":\"png\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":195487,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eDissociation effect of catalysts with different metal centers in DEA system at 160 \\u003c/strong\\u003e\\u003csup\\u003e\\u003cstrong\\u003eo\\u003c/strong\\u003e\\u003c/sup\\u003e\\u003cstrong\\u003eC.\\u003c/strong\\u003e (a) Dissociation rate of DMPC with different metal center catalysts over time. (b) Dissociation rate of DPU with different metal center catalysts over time. (c) Dissociation specific activity of catalysts with different metal centers for \\u003cstrong\\u003etwo-step\\u003c/strong\\u003e reaction of DPU. (d) Dissociation specific activity of catalysts with different metal centers for the \\u003cstrong\\u003estep 1\\u003c/strong\\u003e reaction of DMPC. (e) Dissociation specific activity of catalysts with different metal centers for the \\u003cstrong\\u003estep 2\\u003c/strong\\u003e reaction of DMPC.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"4.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/760349948bb1e88fdb3fed7d.png\"},{\"id\":85381542,\"identity\":\"a6b574e6-cb1f-4aba-a950-6035a4a814c9\",\"added_by\":\"auto\",\"created_at\":\"2025-06-25 09:22:48\",\"extension\":\"png\",\"order_by\":5,\"title\":\"Figure 5\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":170468,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eDissociation mechanism and dissociation rate of carbamate oligomer (CbO).\\u003c/strong\\u003e (a) GC-MS chromatogram of CbO at 160 \\u003csup\\u003eo\\u003c/sup\\u003eC and 300 minutes, (b-d) Mass spectrum of the peaks. (e) Dissociation path of CbO under DEA. (f) The degradation rate of CbO in no catalyst DEA system at 160 \\u003csup\\u003eo\\u003c/sup\\u003eC changes with time. (g) The degradation rate of CbO in TMG/Cd/HMMI catalyst DEA system at 160 \\u003csup\\u003eo\\u003c/sup\\u003eC changes with time.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"5.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/e7c887ce97629d7dfda5ca8b.png\"},{\"id\":85386886,\"identity\":\"f79c5efc-1d7c-40e9-9f41-e595e89c8e90\",\"added_by\":\"auto\",\"created_at\":\"2025-06-25 09:54:48\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":2549298,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/8f2e0f0a-5486-4855-9b71-460130be2029.pdf\"},{\"id\":85382604,\"identity\":\"491edf4d-068e-45bb-bcdf-d61c96323b47\",\"added_by\":\"auto\",\"created_at\":\"2025-06-25 09:30:47\",\"extension\":\"docx\",\"order_by\":1,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":363443,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"TableofContents.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/4b968414d2b4d565338e7ead.docx\"},{\"id\":85382606,\"identity\":\"4bb1e621-7eb7-4a6a-b0cf-81dfe21c2eea\",\"added_by\":\"auto\",\"created_at\":\"2025-06-25 09:30:48\",\"extension\":\"docx\",\"order_by\":2,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":3257704,\"visible\":true,\"origin\":\"\",\"legend\":\"Supplementary Information for Synergistic Bimetallic Catalysis for Closed-Loop Polyurethane Foam Upcycling via Proximity-Driven Depolymerization\",\"description\":\"\",\"filename\":\"SupplementaryInformation.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/02e0334192c5ae1ecb83d0e7.docx\"},{\"id\":85381532,\"identity\":\"0af277fa-e75d-47d7-bf63-8f0fba116c83\",\"added_by\":\"auto\",\"created_at\":\"2025-06-25 09:22:47\",\"extension\":\"docx\",\"order_by\":3,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":1155292,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"ExtendedDataFigs.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6709291/v1/2887f53f230de3895fd7d957.docx\"}],\"financialInterests\":\"There is \\u003cb\\u003eNO\\u003c/b\\u003e Competing Interest.\",\"formattedTitle\":\"Synergistic Bimetallic Catalysis for Closed-Loop Polyurethane Foam Upcycling via Proximity-Driven Depolymerization\",\"fulltext\":[{\"header\":\"Introduction\",\"content\":\"\\u003cp\\u003eThe escalating accumulation of plastic waste poses a dire threat to global ecosystems\\u003csup\\u003e \\u003cspan additionalcitationids=\\\"CR2 CR3 CR4 CR5\\\" citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e \\u003c/sup\\u003e, with polyurethane (PU) a versatile polymer integral to foams, elastomers, and coatings\\u0026mdash;representing 8% of annual plastic production. According to projections from a report published by Grand View Research, the global polyurethane market size is estimated to reach approximately \\u003cspan\\u003e$\\u003c/span\\u003e88\\u0026nbsp;billion by 2025 (corresponding to a consumption volume of around 25\\u0026ndash;28\\u0026nbsp;million metric tons). Conventional disposal methods, such as incineration and landfilling, exacerbate environmental degradation while squandering valuable resources\\u003csup\\u003e \\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e \\u003c/sup\\u003e. Although physical recycling offers partial mitigation, it often compromises material performance. Chemical recycling, which depolymerizes PU into reusable monomers, holds promise but remains hindered by harsh chemical conditions (\\u0026gt;\\u0026thinsp;210\\u0026deg;C, 6\\u0026ndash;12 h reaction time), excessive degradation agent consumption (agent to PUF mass ratios of 1:1 to 4:4), and hazardous byproducts (e.g., uncontrolled pyrolysis products from thermal degradation).\\u003csup\\u003e \\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e \\u003c/sup\\u003e. Therefore, there is an urgent need to design efficient and safe catalytic degradation systems to develop more effective and environmentally friendly recycling pathways that can achieve higher degrees of PU depolymerization under mild or even more favorable conditions.\\u003c/p\\u003e \\u003cp\\u003ePolyurethane foam (PUF), constituting over 50% of global PU consumption, poses formidable challenges for chemical recycling due to its three-dimensional cross-linked network architecture. In recent years, extensive research has been conducted on the degradation of PUF using amine-based catalysts, nitrogen-containing heterocyclic catalysts, and metal catalysts\\u003csup\\u003e\\u003cspan citationid=\\\"CR11\\\" class=\\\"CitationRef\\\"\\u003e11\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u003c/sup\\u003e. Key factors in catalyst design include enhancing the nucleophilicity of the degradation agents and increasing the electrophilicity of the carbamate bonds\\u003csup\\u003e\\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR14\\\" citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e\\u003c/sup\\u003e. Meanwhile, since PUF are three-dimensional cross-linked thermosetting polymers, the issue of reaction collision probability must be considered from a practical application perspective\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR17 CR18 CR19\\\" citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e\\u003c/sup\\u003e. Additionally, the presence of metal elements can significantly influence the reaction between polyols and isocyanates during PUF synthesis, necessitating careful consideration of metal residue. These two aspects are often overlooked in current research. Enzyme-mediated depolymerization under mild conditions holds significant promise for sustainable plastic recycling and environmental remediation. A key mechanistic advantage of enzymatic systems lies in their proximity effect\\u0026mdash;a phenomenon where substrate-binding clefts spatially confine reactive groups (e.g., carbonyl and hydroxyl moieties), effectively mimicking elevated local reactant concentrations to lower activation barriers. This strategy, widely employed by natural hydrolytic enzymes (e.g., cutinases, lipases), has inspired biomimetic approaches for synthetic polymer degradation. A prevailing strategy involves constructing structural analogs or functional mimics of hydrolytic enzyme active sites\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR22 CR23 CR24\\\" citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e21\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e25\\u003c/span\\u003e\\u003c/sup\\u003e. Zhang et al\\u003csup\\u003e\\u003cspan citationid=\\\"CR22\\\" class=\\\"CitationRef\\\"\\u003e22\\u003c/span\\u003e\\u003c/sup\\u003e. biomimetic designs leveraging binuclear metallohydrolases, achieving efficient polyethylene terephthalate (PET) degradation. Inspired by these mechanistic parallels, we explored the feasibility of adapting analogous synergistic strategies\\u0026mdash;particularly proximity-driven dinuclear catalysis\\u0026mdash;to the alcoholysis/aminolysis of PUF.\\u003c/p\\u003e \\u003cp\\u003eIn this work (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e), a ternary catalyst featuring a bimetallic Cd (di-Cd\\u0026sup2;⁺) catalytic center was synthesized by coordinating with 1,1,3,3-tetramethylguanidine (TMG) and 1-methyl-2-hydroxymethylimidazole (HMMI), demonstrating synergistic catalytic effects. In this system, the carbamate bond and the degradation agent are bound to the metal center, bringing the reactants into closer proximity and effectively converting intermolecular reactions into intramolecular reactions, thereby increasing the likelihood of collisions. TMG\\u0026rsquo;s strong basicity activates degradation agents and stabilizes intermediates, while HMMI modulates electron density at the metal center and enhances solubility via its terminal hydroxyl group. The distinct catalytic mechanisms of these three components simultaneously increase the nucleophilicity of the degradation agent and the electrophilicity of the carbamate bond. By integrating the catalyst with a multi-stage degradation strategy, we achieved complete cleavage of carbamate and urea bonds in polyurethane foam (PUF) under mild conditions (180\\u0026ndash;200\\u0026deg;C, 4 h, 10 wt% degradation agent relative to PUF mass), enabling spontaneous phase separation into high-purity recycled polyols (RP) and isocyanate-derived hard segments (HS) without requiring purification. The RP exhibit near-identical properties to virgin polyols (hydroxyl value: 66 mgKOH g⁻\\u0026sup1;; viscosity: 950 mPa\\u0026middot;s) and can replace 40 wt% of virgin feedstock in new foam synthesis without sacrificing mechanical integrity. At the same time, the hard segments are repurposed as reinforcing additives for rigid foams, improving the mechanical properties. This closed-loop strategy eliminates purification steps, minimizes waste, and aligns with circular economy principles.\\u003c/p\\u003e \\u003cp\\u003eBy bridging enzymatic mimicry with metal coordination chemistry, our work redefines catalytic PUF recycling, offering a scalable pathway to mitigate plastic pollution while reclaiming value from waste.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e\"},{\"header\":\"Results and discussion\",\"content\":\"\\u003cdiv id=\\\"Sec3\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eCharacterization of catalyst\\u003c/h2\\u003e \\u003cp\\u003eThe ternary catalyst TMG/Cd/HMMI was synthesized by reacting 1,1,3,3-tetramethylguanidine (TMG), 1-methyl-2-hydroxymethylimidazole (HMMI), and cadmium nitrate in acetone at 60\\u0026deg;C for 4 hours (\\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea; full protocols in the section \\u0026lsquo;Materials and general measurements\\u0026rsquo; in Methods). To confirm the complex formation and stoichiometry, the raw materials and final product were analyzed via \\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003eH NMR spectroscopy (\\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003eb). Compared to free HMMI, the proton signals of HMMI in the complex exhibited downfield shifts, attributed to electron density loss upon coordination. Integration of key proton environments (H1 from TMG and H2 from HMMI) revealed a 4:1 ratio (\\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ec), confirming a 1:1 molar ratio of TMG to HMMI in the catalyst.\\u003c/p\\u003e \\u003cp\\u003eThe successful synthesis of the TMG/Cd/HMMI complex was further confirmed through spectroscopic and thermal analyses. UV-Vis spectroscopy revealed a distinct blue shift in the absorption band of HMMI after coordination (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea), indicating electronic interaction between the ligand and Cd(II) center. X-ray photoelectron spectroscopy (XPS) analysis demonstrated a 1.32 eV reduction in the Cd 3d₅/₂ binding energy (405.08 eV for TMG/Cd/HMMI vs. 406.4 eV for cadmium nitrate; Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb, \\u003cb\\u003eTable S1\\u003c/b\\u003e\\u003csup\\u003e26\\u003c/sup\\u003e), attributed to increased electron density around cadmium ions upon ligand coordination. Further analysis of the N 1s spectrum resolved four distinct nitrogen environments (401.06, 400.40, 399.23, and 398.57 eV; Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ec), corresponding to coordinated nitrogen atoms from TMG and HMMI. Elemental analysis via organic elemental analysis (OEA, \\u003cb\\u003eTable S2\\u003c/b\\u003e), inductively coupled plasma-mass spectrometry (ICP-MS, \\u003cb\\u003eTable S2\\u003c/b\\u003e), and thermogravimetric analysis (TGA, Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ed) confirmed the catalyst composition. ICP-MS and TGA revealed mutually corroborating cadmium contents of 36.19% (\\u003cb\\u003eTable S2\\u003c/b\\u003e) and 37.27% (\\u003cb\\u003eTable S3\\u003c/b\\u003e), respectively. TGA further demonstrated enhanced thermal stability of the complex after ligand coordination, with no decomposition observed within the degradation temperature range (160\\u0026ndash;200\\u0026deg;C). Energy-dispersive X-ray spectroscopy (EDS) line scans verified the homogeneous distribution of N, O, and Cd throughout the catalyst structure (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ee-f).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eThe atomic structure of TMG/Cd/HMMI was further analyzed using X-ray absorption fine structure (XAFS) spectroscopy. X-ray absorption near-edge structure (XANES) analysis revealed a distinct red shift in the Cd K-edge absorption energy of TMG/Cd/HMMI compared to CdO and CdS (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea), suggesting the oxidation state of the Cd atoms in TMG/Cd/HMMI was below +\\u0026thinsp;2. EXAFS fitting (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ej) further confirmed the presence of direct Cd\\u0026ndash;Cd interactions (coordination number: 1.2; bond length: 2.39 \\u0026Aring;), alongside Cd\\u0026ndash;O/N coordination (coordination number: 4.3; bond length: 2.27 \\u0026Aring;, \\u003cb\\u003eTable S4\\u003c/b\\u003e). These findings unambiguously establish TMG/Cd/HMMI as a dinuclear complex with a Cd\\u0026ndash;Cd metallic bond. The shortened Cd\\u0026ndash;Cd distance (relative to Cd-foil, 2.94 \\u0026Aring;\\u003csup\\u003e\\u003cspan citationid=\\\"CR27\\\" class=\\\"CitationRef\\\"\\u003e27\\u003c/span\\u003e\\u003c/sup\\u003e) suggests significant electron delocalization between the two Cd centers, likely contributing to the system\\u0026rsquo;s exceptional catalytic activity through cooperative bond activation.\\u003c/p\\u003e \\u003c/div\\u003e\\n\\u003ch3\\u003eInvestigation of catalytic effect and mechanism of TMG/Cd/HMMI\\u003c/h3\\u003e\\n\\u003cp\\u003ePolyurethane foam (PUF), a three-dimensional cross-linked network synthesized from diisocyanates and polyols using water as a blowing agent and amine/tin catalysts, contains diverse functional groups (e.g., carbamate, urea, ether linkages) that complicate degradation mechanism studies. To address this, we designed two small-molecule models\\u0026mdash;structurally analogous to PUF\\u0026mdash;to specifically mimic carbamate (diethyl (4-methyl-1,3-phenylene) dicarbamate, DMPC) and urea (N,N-diphenyl urea, DPU) linkages, enabling systematic investigation of degradation and catalytic pathways. (The details of synthesis and characterization are in the \\u0026lsquo;Model Compound Experiment\\u0026rsquo; section of the Methods.)\\u003c/p\\u003e \\u003cp\\u003eThe catalytic performance and mechanism of TMG/Cd/HMMI were systematically investigated using DMPC and DPU as model substrates under mild conditions (Detailed degradation formulations and procedures are provided in the section \\u0026lsquo;Model compound experiments\\u0026rsquo; in Methods. Kinetic calculations were reported in our prior publication\\u003csup\\u003e\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e\\u003c/sup\\u003e). Kinetic analysis revealed a biphasic degradation process for DPU (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea), with activation energies of 97.6\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;11.2 kJ mol⁻\\u0026sup1; (step 1) and 139.0\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;14.3 kJ mol⁻\\u0026sup1; (step 2), reflecting distinct energy barriers for sequential bond cleavage (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea). Similarly, DMPC degradation proceeded stepwise: ethanol release (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003eb, step 1) preceded toluene-2,4-diamine (TDA) formation (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003eb, step 2). TMG/Cd/HMMI outperformed its individual components (Cd(NO₃)₂, TMG, HMMI; Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ec\\u0026ndash;e), enhancing aniline yields by 25% (vs. Cd(NO₃)₂), 72% (vs. TMG), and 107% (vs. HMMI) for DPU at 60 min, and boosting TDA production by 249%, 780%, and 659% for DMPC at 180 min, respectively. Comparative studies with conventional catalysts further demonstrated TMG/Cd/HMMI\\u0026rsquo;s superior activity in both DPU dissociation and TDA formation (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ef\\u0026ndash;h).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eBased on the above discussion, the influence of metal ions on catalytic efficiency is particularly pronounced. Therefore, we synthesized dual-ligand metal complexes using the same ligands but incorporating different metal ions. Comparative studies of dual-ligand metal complexes with identical ligands but varying metal centers revealed Cd(II)\\u0026rsquo;s exceptional catalytic performance in cleaving both carbamate (DMPC) and urea (DPU) bonds, with activity hierarchies of Cd(II)\\u0026thinsp;\\u0026gt;\\u0026thinsp;Co(II)\\u0026thinsp;\\u0026gt;\\u0026thinsp;Cu(II)\\u0026thinsp;\\u0026gt;\\u0026thinsp;Ni(II)\\u0026thinsp;\\u0026gt;\\u0026thinsp;Zn(II) for DMPC (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ea, \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ed-e) and Cd(II)\\u0026thinsp;\\u0026gt;\\u0026thinsp;Ni(II)\\u0026thinsp;\\u0026gt;\\u0026thinsp;Zn(II)\\u0026thinsp;\\u0026gt;\\u0026thinsp;Co(II)\\u0026thinsp;\\u0026gt;\\u0026thinsp;Cu(II) for DPU (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003eb, \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ec). This remarkable advantage of Cd(II) may come from its unique structure and electronic properties. The relatively large ionic radius of Cd(II) (0.95 \\u0026Aring;) enhances coordination flexibility, enabling diverse geometries that accommodate multiple ligands while providing spatial freedom for carbonyl group activation and reactant positioning near catalytic sites. This structural adaptability facilitates rapid product release and efficient polarization of the carbonyl moiety during reactions. Complementing this, Cd(II)\\u0026rsquo;s closed-shell [Kr]4d\\u0026sup1;⁰ electronic configuration minimizes π-backbonding and orbital hybridization, allowing the metal to prioritize strong σ-coordination with ligands. This focused electronic interaction stabilizes the catalytic complex and enhances its ability to sustain electron withdrawal from the carbonyl group, thereby lowering activation barriers.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eTo elucidate ligand roles in the TMG/Cd/HMMI system, we decoupled the ternary complex into pairwise combinations (TMG/Cd, Cd/HMMI, TMG/HMMI) and assessed their catalytic efficiencies via the second-stage DMPC degradation (TDA formation). TMG/Cd coordination proved pivotal, enhancing TDA yields by 623% (vs. TMG) and 190% (vs. Cd(NO₃)₂) at 180 min (\\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea), attributed to TMG\\u0026rsquo;s strong basicity enabling degradation agent (diethanolamine, DEA) deprotonation. Screening cadmium salts with varying anion basicities (OH⁻ \\u0026gt; CH₃COO⁻ \\u0026gt; NO₃⁻) confirmed ligand basicity-activity correlations (TMG/Cd\\u0026thinsp;\\u0026gt;\\u0026thinsp;Cd(OH)₂ \\u0026gt; Cd(OAc)₂ \\u0026gt; Cd(NO₃)₂; \\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb). ICP-MS revealed exceptional Cd loading (80.38 wt%, \\u003cb\\u003eTable S5\\u003c/b\\u003e) in TMG/Cd, suggesting the formation of Cd-Cd metallic bonds that may amplify electron delocalization at active sites. Introducing HMMI reduced Cd content to 36.33 wt% but paradoxically increased catalytic efficiency by 21% (vs. TMG/Cd) and 197% (vs. Cd/HMMI), owing to its dual roles: (1) imidazole-mediated electron transfer lowering transition-state barriers, and (2) HMMI can promote the complete dissolution of catalyst in DEA within 10 minutes at 160\\u0026deg;C (vs. 9.26% for TMG/Cd; \\u003cb\\u003eTable S6\\u003c/b\\u003e). These findings establish a synergistic paradigm: TMG optimizes bond activation via basicity, while HMMI regulates electron transport and solubility, overcoming limitations of single-ligand systems.\\u003c/p\\u003e\\n\\u003ch3\\u003eDegradation of carbamate oligomer\\u003c/h3\\u003e\\n\\u003cp\\u003eSince the previous discussions were based on the small molecule models DMPC (carbamate bond) and DPU (urea bond), which differ significantly from polymers in terms of primary, secondary, and tertiary structures, we synthesized a linear carbamate oligomer (CbO, Mₙ = 3,147 Da) to further investigate and validate the degradation mechanism and catalytic behavior (\\u003cb\\u003eFig. S2\\u003c/b\\u003e). The synthesis procedure and basic data for CbO can be found in the section \\u0026lsquo;Model compound experiments\\u0026rsquo; in Methods. First, we explored the degradation mechanism of CbO, with detailed experimental procedures outlined in the section \\u0026lsquo;Model compound experiments\\u0026rsquo; in Methods. Degradation of CbO in the presence of TMG/Cd/HMMI unveiled a two-step mechanism (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ee): initial nucleophilic attack by DEA at carbamate bonds releases diethylene glycol (DEG, Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ec), followed by hydroxyl-terminated intermediate cyclization to yield 4,4'-methylenedianiline (MDA, Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ed) and 3-(2-hydroxyethyl)oxazolidin-2-one (MDA, Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003eb). This pathway, corroborated by GC-MS identification of all intermediates (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ea-d), confirming consistency with the stepwise degradation observed in the small-molecule DMPC model, and verified the rationality of the small molecule model as a prediction tool for polymer degradation.\\u003c/p\\u003e \\u003cp\\u003eTo quantify catalytic efficiency in polymeric contexts, we monitored DEG and MDA production kinetics under catalytic and non-catalytic conditions. As demonstrated in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ef, in the presence of TMG/Cd/HMMI, the degradation of CbO is higher than that of non-catalytic system by \\u0026gt;\\u0026thinsp;433% within 150 minutes. This further confirms the effectiveness of the the catalyst maintained stability without deactivation, even in the presence of long-chain polymer segments.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eThe catalytic mechanism was investigated by monitoring the reaction process through infrared (FTIR) spectroscopy. The results are shown in \\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea. In the IR spectrum, the N-H stretching vibration, typically appearing between 3300\\u0026ndash;3500 cm⁻\\u0026sup1; and primarily originating from the amino groups in both carbamate bonds and DEA, exhibited a blue shift from 3281 cm⁻\\u0026sup1; to 3308 cm⁻\\u0026sup1; upon the introduction of TMG/Cd/HMMI. This shift indicates that the addition of the catalyst disrupts the original hydrogen-bond network, allowing the N-H bonds to vibrate more freely, thereby increasing the vibrational frequency. Simultaneously, the electron cloud density around the amino groups in DEA is enhanced, which increases their reactivity. A similar blue shift was observed in the N-H bending vibration, which shifted from 1594 cm⁻\\u0026sup1; to 1607 cm⁻\\u0026sup1; following the addition of TMG/Cd/HMMI. Moreover, the ester bond stretching vibration peak also shifted from 1707 cm⁻\\u0026sup1; to 1725 cm⁻\\u0026sup1;, suggesting that the coordination of TMG/Cd/HMMI with the carbonyl oxygen induces electron transfer towards the oxygen atom, enhancing the positive charge on the carbonyl carbon, thereby making it more prone to nucleophilic attack by DEA.\\u003c/p\\u003e \\u003cp\\u003eBuilding on these observations, the catalytic mechanism can be proposed as follows (\\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003eb, \\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ec): The dinuclear Cd(II) center orchestrates both proximity control and electronic activation. First, it spatially confines DEA\\u0026rsquo;s amine groups and carbamate carbonyl oxygen through simultaneous coordination, effectively converting intermolecular reactions into pseudo-intramolecular processes with elevated local substrate concentrations. Second, Cd(II)\\u0026rsquo;s strong electron-withdrawing capacity polarizes the carbonyl group, lowering the activation barrier for nucleophilic cleavage. This bifunctional action is synergistically amplified by HMMI\\u0026rsquo;s electron-transfer mediation and TMG\\u0026rsquo;s basicity, which respectively optimize charge transfer kinetics and substrate deprotonation.\\u003c/p\\u003e\\n\\u003ch3\\u003eDegradation of Waste Polyurethane Foam (PUF)\\u003c/h3\\u003e\\n\\u003cdiv id=\\\"Sec7\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eDEA Degradation System (Catalytic Effect Verification)\\u003c/h2\\u003e \\u003cp\\u003eBased on the previously established catalytic mechanism, we applied the TMG/Cd/HMMI catalytic degradation system to the degradation of waste polyurethane foam (PUF). The degradation of PUF was evaluated under mild conditions (180\\u0026deg;C, using DEA as the degrading agent), with detailed degradation formulations and procedures provided in the section \\u0026lsquo;Degradation of Waste Polyurethane Foam (PUF)\\u0026rsquo; in Methods. In the presence of TMG/Cd/HMMI, the system achieved complete liquefaction within 39 minutes, followed by spontaneous phase separation into a low-viscosity recycled polyol phase (RP, 950 mPa\\u0026middot;s) and an isocyanate-derived hard segment (HS) (\\u003cb\\u003eFig. S3\\u003c/b\\u003e), which is remarkable given that the amount of DEA used was only 10 wt% of the PUF. In contrast, traditional catalysts (e.g., Zn(OAc)₂, TMEDA, DMCHA), under the same conditions, failed to obtain low viscosity RP (\\u003cb\\u003eFig. S4\\u003c/b\\u003e, Table\\u0026nbsp;\\u003cspan refid=\\\"Tab1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e). An analysis of the small molecule dissociation results provides insights into the phase separation mechanism observed during PUF degradation in the TMG/Cd/HMMI system. In most other catalytic degradation systems, only partial C-O bonds and a very limited number of C-N bonds (isocyanate segments) are cleaved, leaving the isocyanate segments attached to the polyol chain. These isocyanate fragments, typically associated with short chains containing aromatic structures, increase the viscosity of the system. However, the TMG/Cd/HMMI system can effectively activates DEA, promoting its attack on both carbamate and urea bonds. This leads to complete cleavage of C\\u0026ndash;N bonds, fully liberating the isocyanate segments from the polyol backbone. Furthermore, due to the partial compatibility between the isocyanate segments and the polyol phase, spontaneous phase separation occurs upon standing without requiring any additional processing. Although TMG/Cd/HMMI exhibits high catalytic efficiency, the potential toxicity of Cd(II) necessitates careful examination of its distribution in degradation products. ICP-MS analysis of both the recycled polyol (RP) and hard segment (HS) revealed negligible Cd(II) residues in the RP (8 ppm, \\u003cb\\u003eTable S7\\u003c/b\\u003e)\\u0026mdash;well below the heavy metal content limits for the flexible foam furniture industry. This confirms the RP\\u0026rsquo;s practical applicability while ensuring compliance with environmental and safety standards.\\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab1\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 1\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eDegradation of PUF under Different Catalysts.\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"5\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eentry\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003edegradation agent\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003ecatalyst\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003etime\\u003csup\\u003e\\u003cem\\u003ea\\u003c/em\\u003e\\u003c/sup\\u003e (min)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eRP viscosity (mPa\\u0026middot;s)\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eDEA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e/\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e90\\u0026ndash;120\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e12700\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e2\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eDEA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eTMG\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e40\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e13600\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e3\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eDEA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eMMI\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e60\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e5560\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eDEA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eZn(OAC)\\u003csub\\u003e2\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e70\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e3050\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e5\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eDEA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eDMCHA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e70\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e3870\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e6\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eDEA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eTMEDA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e90\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e3100\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eDEA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003ePMDETA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e70\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e6570\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eDEA\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eTMG/Cd/HMMI\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e39\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e950\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e\\u003cp\\u003e\\u003cem\\u003e\\u003csup\\u003ea: Time required to put in 100g foam.\\u003c/sup\\u003e\\u003c/em\\u003e\\u003c/p\\u003e\\u003c/div\\u003e \\u003cdiv id=\\\"Sec8\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eMultistage Degradation System (Practical application of catalyst)\\u003c/h2\\u003e \\u003cp\\u003eTo further evaluate the practical application potential of TMG/Cd/HMMI, we integrated it into the multi-stage degradation system. The operational principles and mechanistic insights of this multi-stage degradation system have been detailed in our previous work\\u003csup\\u003e\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e\\u003c/sup\\u003e (See in the section ' Degradation of Waste Polyurethane Foam (PUF)\\u0026rsquo; in Methods for specific degradation formulations and procedures). Characterization of the RP (\\u003cb\\u003eTable S8\\u003c/b\\u003e) confirmed complete cleavage of polyol-isocyanate linkages, enabling spontaneous phase separation into RP and isocyanate-derived hard segments (HS). The hydroxyl value (HV) of RP-TMG/Cd/HMMI slightly exceeded that of virgin polyol (VP), which is attributed to trace residual DEA. Since DEA inherently acts as a catalyst in polyurethane foaming, no further purification is required\\u0026mdash;only an adjustment of amine catalyst dosage during re-foaming is necessary. Subsequently, RP-TMG/Cd/HMMI was employed to partially replace VP (0\\u0026ndash;40 wt%) in synthesizing flexible polyurethane foams (Foaming formulations and protocols are provided in the section \\u0026lsquo;Re-foaming experiment of recycled polyol\\u0026rsquo; in Methods). Digital photos and SEM images of flexible regenerated polyurethane foam (Flexible - RPUF) with varying RP contents (\\u003cb\\u003eFig. S5\\u003c/b\\u003e) revealed preserved structural integrity in RPUF-40RP, exhibiting well-defined cellular architecture with only marginal yellowing. As shown in \\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ea, \\u003cb\\u003eTable S10\\u003c/b\\u003e the mechanical properties of Flexible - RPUF with 40 wt% RP substitution remained compliant with commercial standards.\\u003c/p\\u003e \\u003cp\\u003eThe isocyanate-derived hard segments generated during depolymerization comprising amide derivatives with residual polyol fragments exhibit dual functionality: partial compatibility with virgin polyols and inherent structural rigidity. Capitalizing on these traits, HS were repurposed as reinforcing fillers for rigid polyurethane foams, analogous to calcium carbonate additives. Pre-crushed HS were blended with PPG via ball milling prior to foaming. Detailed protocols in the section \\u0026lsquo;Re-foaming experiment of recycled polyol\\u0026rsquo; in Methods. Incorporation of HS increased polyol viscosity and caused mild discoloration in both recycled polyols and foams (\\u003cb\\u003eFig. S6, Table S9\\u003c/b\\u003e). At 40 wt% loading, rigid regenerated polyurethane foam (Rigid - RPUF) exhibited significant enhancements (\\u003cb\\u003eExtended Data\\u003c/b\\u003e Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003eb, \\u003cb\\u003eTable S11\\u003c/b\\u003e): 27.15% higher density, 34.53% greater hardness, and 202.88% improved 10% compressive strength versus HS-free counterparts. This strategy not only eliminates HS waste but also aligns with circular economy principles by transforming byproducts into value-added materials.\\u003c/p\\u003e \\u003c/div\\u003e\\n\\u003ch3\\u003eCalculation of environmental energy impact\\u003c/h3\\u003e\\n\\u003cp\\u003eA rigorous sustainability assessment was conducted to benchmark the TMG/Cd/HMMI system against conventional catalytic approaches using the tripartite green chemistry metrics proposed by Thelemans et al. and Zhang et al.\\u003csup\\u003e\\u003cspan citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e28\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR29\\\" class=\\\"CitationRef\\\"\\u003e29\\u003c/span\\u003e\\u003c/sup\\u003e: energy economy (ε), environmental factor (E), and environmental-energy impact (ξ) (See in the section \\u0026lsquo;Calculation of environmental energy impact\\u0026rsquo; in Methods for calculation method). Ideal depolymerization processes are characterized by maximized ε alongside minimized E and ξ. As quantified in \\u003cb\\u003eTables S12, S13\\u003c/b\\u003e, TMG/Cd/HMMI outperforms traditional catalysts, achieving exceptional ε values of 2.95\\u0026times;10⁻\\u0026sup3; and 9.72\\u0026times;10⁻\\u0026sup3; \\u003csup\\u003eo\\u003c/sup\\u003eC\\u003csup\\u003e\\u0026minus;1\\u003c/sup\\u003e\\u0026middot;min\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e for carbamate and urea bond cleavage, respectively. Concurrently, it maintains ultralow environmental impact (E: 3.05 and 0.34; ξ: 1.04\\u0026times;10\\u0026sup3; and 35.06 \\u003csup\\u003eo\\u003c/sup\\u003eC\\u0026middot;min). This dual optimization of energy efficiency and environmental compatibility underscores the system\\u0026rsquo;s unique potential for scalable polyurethane upcycling.\\u003c/p\\u003e\"},{\"header\":\"Conclusions\",\"content\":\"\\u003cp\\u003eThe relentless accumulation of PUF waste demands catalytic technologies that balance efficiency, sustainability, and practicality. In this study, we address this challenge through the rational design of TMG/Cd/HMMI, a ternary catalyst that leverages the complementary roles of TMG (basicity), HMMI (electron transfer, compatibility), and Cd(II) (electrophilic activation) to depolymerize PUF under mild conditions. By coordinating Cd(II) with TMG and HMMI, we create a dinuclear catalytic center that accelerates bond cleavage via a proximity effect, effectively converting intermolecular reactions into intramolecular processes. This mechanism ensures complete degradation of PUF under mild conditions (180\\u0026ndash;200\\u0026deg;C, 4 h, 10% degradation agent relative to PUF mass) into phase-separated RP and hard segments. The RP retain commercial-grade properties (e.g., hydroxyl value: 66 mgKOH g⁻\\u0026sup1;, viscosity: 950 mPa\\u0026middot;s) and directly replace virgin polyols in foam production, while the hard segment can enhance the strength of rigid foam by mixing with polyol. This work not only advances catalytic PUF recycling but also redefines waste valorization by transforming \\\"non-recyclable\\\" hard segments into reinforcing fillers. Our findings illuminate a pathway toward industrial-scale plastic upcycling, where catalytic design aligns with circular economy principles to reconcile ecological and economic imperatives.\\u003c/p\\u003e\"},{\"header\":\"Methods\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003eMaterials and general measurements\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eMaterials.\\u0026nbsp;\\u003c/strong\\u003eDuring the catalyst synthesis, cadmium nitrate (Cd(NO₃)₂\\u0026middot;H₂O), 1,1,3,3-tetramethylguanidine (TMG), and 1-methyl-2-hydroxymethylimidazole (HMMI) (all supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) were used. PUFs waste (supplied by Sinomax (Zhejiang) Polyurethane Technology Limited.) uses diethanolamine (supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) and succinic acid (supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) as degradation agents for multi-stage degradation. In the synthesis of model molecules, anhydrous ethanol, diethylene glycol, and methylene diphenyl diisocyanate (MDI) (all supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) were employed. The model molecule 1,3-diphenylurea (DPU) was supplied by Shanghai Aladdin Biochemical Technology Co., Ltd. For regenerated foam production, traditional petroleum-based polyol (PPG5623, supplied by Zhejiang Hengfeng New Material Co., Ltd.), JB-635C polyol (supplied by Jiangsu Zhongshan Chemical Co., Ltd.), 2,4-toluene diisocyanate (TDI), polymeric methylene diphenyl diisocyanate (PAPI) (supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.), silicone surfactant (silicone oil, supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.), foaming agent (distilled water), and catalysts (triethylamine, dibutyltin dilaurate, and stannous octoate, supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.) were utilized.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eSynthesis of TMG/Cd/HMMI.\\u0026nbsp;\\u003c/strong\\u003eCd(NO₃)₂\\u0026middot;H₂O (86.9 mmol), TMG (86.9 mmol), HMMI (86.9 mmol), and 50 mL acetone were added to a 250 mL three-neck flask, and the mixture was reacted at 60 \\u0026deg;C for 4 hours (\\u003cstrong\\u003eExtended Data Fig. 1\\u003c/strong\\u003e). After the reaction, the product was filtered and washed with deionized water. Finally, the product was dried in a vacuum oven at 80\\u0026deg;C for 48 hours, then ground to obtain TMG/Cd/HMMI with an 80% yield.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eGeneral measurements.\\u003csup\\u003e\\u0026nbsp;1\\u003c/sup\\u003eH NMR\\u003c/strong\\u003e spectra were recorded using a Bruker AVANCE NEO 400 MHz instrument (Bruker Corporation, USA) at room temperature in DMSO-\\u003cem\\u003ed\\u003csub\\u003e6\\u003c/sub\\u003e\\u003c/em\\u003e. Chemical shifts are given in ppm relative to a DMSO-\\u003cem\\u003ed\\u003csub\\u003e6\\u003c/sub\\u003e\\u003c/em\\u003e residual peak. \\u0026nbsp;The change of integral area of proton peak of DMPC and DPU with reaction time was monitored to evaluate the catalytic effect under different catalysts. The transparency of TMG/Cd/HMMI were measured by \\u003cstrong\\u003eUV-vis\\u003c/strong\\u003e spectrophotometer (PerkinElmer, Lambda750s, USA). X-ray photoelectron spectroscopy (\\u003cstrong\\u003eXPS\\u003c/strong\\u003e, Esca Lab 250X, Thermo Fisher, USA) is used to analyze the changes of binding energy of elements in TMG/Cd/HMMI. Thermogravimetric analyzer (\\u003cstrong\\u003eTG\\u003c/strong\\u003e, 209 F1, Netzsch Germany) is used to test the thermal stability of CbO and TMG/Cd/HMMI. The thermal stability of the sample was analyzed at the rate of 10 \\u003csup\\u003eo\\u003c/sup\\u003eC /min from room temperature to 600 \\u003csup\\u003eo\\u003c/sup\\u003eC in air or nitrogen. Differential scanning calorimetry (\\u003cstrong\\u003eDSC\\u003c/strong\\u003e) is used to test the thermal behavior of CbO in nitrogen atmosphere. The samples were drop coated on amorphous carbon-coated Cu grids. \\u003cstrong\\u003eTEM\\u003c/strong\\u003e images were recorded by using a JEM-1010 microscope at an accelerating voltage of 80 kV. Data reduction, data analysis, and \\u003cstrong\\u003eEXAFS\\u003c/strong\\u003e fitting were performed and analyzed with the Athena and Artemis programs of the Demeter data analysis packages\\u003csup\\u003e30\\u003c/sup\\u003e that utilizes the FEFF6 program\\u003csup\\u003e31\\u003c/sup\\u003e to fit the EXAFS data. The energy was calibrated using the correspond metal foil, which as a reference was simultaneously measured. A linear function was subtracted from the pre-edge region, then the edge jump was normalized using Athena software. The \\u0026chi;(k) data were isolated by subtracting a smooth, third-order polynomial approximating the absorption background of an isolated atom. The k\\u003csup\\u003e3\\u003c/sup\\u003e-weighted \\u0026chi;(k) data were Fourier transformed after applying a Hanning window function (\\u0026Delta;k = 1.0). For EXAFS modeling, the global amplitude EXAFS (CN, R, \\u0026sigma;\\u003csup\\u003e2\\u003c/sup\\u003e and \\u0026Delta;E\\u003csub\\u003e0\\u003c/sub\\u003e) were obtained by nonlinear fitting, with least-squares refinement, of the EXAFS equation to the Fourier-transformed data in R-space, using Artemis software. For Wavelet Transform analysis, the \\u0026chi;(k) exported from Athena was imported into the Hama Fortran code. The parameters were listed as follow: R range, 0 \\u0026ndash; 6 \\u0026Aring;, k range, 0 - 12.0 \\u0026Aring;-1; k weight, 3; and Morlet function with \\u0026kappa;=10, \\u0026sigma;=1 was used as the mother wavelet to provide the overall distribution\\u003csup\\u003e32\\u003c/sup\\u003e. The \\u003cstrong\\u003eFT-IR\\u003c/strong\\u003e spectra of RP were measured on a Nicolet 6700 Fourier Transform Infrared Spectrometer of Thermo Fisher Company (America) in the wave number range of 650 to 4000 cm\\u003csup\\u003e-1\\u003c/sup\\u003e. The microstructures test was observed by scanning electron microscopy (\\u003cstrong\\u003eSEM\\u003c/strong\\u003e, JEOL JSM-5900LV, Japan) at 10 kV acceleration voltage. Organic element analysis (\\u003cstrong\\u003eOEA\\u003c/strong\\u003e, Thermo Fisher) was used to measure the element content of TMG/Cd/HMMI. Inductively coupled plasma-Mass Spectrometry (\\u003cstrong\\u003eICP-MS\\u003c/strong\\u003e, Thermo Fisher) was used to measure the metal content of catalyst. The molecular weight and dispersity (\\u0026ETH;) of RP were determined by gel permeation chromatography (PL-\\u003cstrong\\u003eGPC\\u003c/strong\\u003e50, Aligent, USA), using THF as solvent and polystyrene as standard sample. The instrument model is \\u003cstrong\\u003eGCMS\\u003c/strong\\u003e-QP2010 Plus (chromatographic columnmodel: DB-17MS; chromatographic column size: 60 m \\u0026times; 250 \\u0026mu;m \\u0026times; 0.25 \\u0026mu;m).\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eModel compound experiments\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eSynthesis of Diethyl (4-Methyl-1,3-Phenylene) Dicarbamate (DMPC) as a Model Compound.\\u0026nbsp;\\u003c/strong\\u003e250 g (5.43 mol) of anhydrous ethanol was weighed into a 500 mL round-bottom flask, and under magnetic stirring and an ice-water bath, 80 g (0.46 mol) of tolylene-2,4-diisocyanate (TDI) was added dropwise to the flask. The reaction temperature was maintained at 0\\u0026deg;C and continued for 2 hours. The resulting reaction mixture was concentrated under reduced pressure at 55\\u0026deg;C using a rotary evaporator to remove excess ethanol, then transferred to a vacuum oven at 70\\u0026deg;C and dried for 48 hours, yielding a white powder, DMPC, with a 93% yield. The \\u003csup\\u003e1\\u003c/sup\\u003eH NMR characterization in DMSO-\\u003cem\\u003ed\\u003csub\\u003e6\\u003c/sub\\u003e\\u003c/em\\u003e is shown in \\u003cstrong\\u003eFig. S1\\u003c/strong\\u003e, confirming the product as diethyl (4-methyl-1,3-phenylene) dicarbamate (DMPC).\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eSynthesis of carbamate oligomer (CbO).\\u0026nbsp;\\u003c/strong\\u003e30 g (282.7 mmol) of diethylene glycol (DEG) was weighed into a 500 mL beaker. At room temperature and under high-speed stirring, 47.16 g (188.5 mmol) of methylene diphenyl diisocyanate (MDI) was rapidly added. After stirring at high speed for 30 s, the mixture was transferred to an oven at 60\\u0026deg;C for 24 h to cure. The cured product was then dissolved in THF and reprecipitated using ethanol as a poor solvent. The resulting precipitate was dried in a vacuum oven at 60\\u0026deg;C for 48 h to yield a white powder designated as carbamate oligomer (CbO), with a yield of 95%. Gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were performed on CbO (\\u003cstrong\\u003eFig. S2\\u003c/strong\\u003e). The results indicated that CbO has a weight-average molecular weight of 5597 and a thermal decomposition temperature of 300 \\u0026deg;C, ensuring that CbO will not undergo thermal degradation at the experimental degradation temperature (160 \\u0026deg;C).\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eDegradation of DMPC.\\u0026nbsp;\\u003c/strong\\u003eDMPC, DEA, and the catalyst were added to a three-neck flask in a molar ratio of 1:5:0.1 and equipped with a reflux condenser. The degradation was carried out at 160\\u0026deg;C. Samples were taken at different reaction times, and the reaction was quantitatively monitored by 1H NMR.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eDegradation of DPU.\\u0026nbsp;\\u003c/strong\\u003eDPU, DEA, and the catalyst were added to a three-neck flask in a molar ratio of 1:2.5:0.1 and equipped with a reflux condenser. The degradation was performed at 160\\u0026deg;C. Samples were taken at different reaction times, and the reaction was quantitatively monitored by 1H NMR.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eDegradation of Carbamate Oligomer.\\u0026nbsp;\\u003c/strong\\u003e10 g of CbO, 8.85 g (84.2 mmol) of DEA, and 2.84 g (5.0 mmol) of TMG/Cd/HMMI were placed in a three-neck flask, and degradation was conducted at 160\\u0026deg;C. Samples were taken at various reaction times, and the reaction was quantitatively monitored by GC-MS. The reaction mechanism was studied using Fourier-transform infrared (FTIR) spectroscopy.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eDegradation of Waste Polyurethane Foam (PUF)\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eDEA Degradation System (Catalytic Effect Verification).\\u0026nbsp;\\u003c/strong\\u003e10 g (95.1 mmol) of DEA, 3.53 g (6.1 mmol) of TMG/Cd/HMMI, and 100 g of PPG were placed in a 500 mL three-neck flask. The flask was placed in an oil bath at 180\\u0026deg;C, and 100 g of crushed PUF was continuously added, with mechanical stirring for 2 hours. The time for complete dissolution of the PUF was recorded, and the temperature was then raised to 200\\u0026deg;C, continuing mechanical stirring for another 2 hours. After the reaction was completed and the mixture was cooled to room temperature, the recovered polyol (RP) was obtained.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eMultistage Degradation System.\\u0026nbsp;\\u003c/strong\\u003e10 g (95.1 mmol) of DEA, 3.53 g (6.1 mmol) of TMG/Cd/HMMI, and 100 g of PPG were placed in a 500 mL three-neck flask. The flask was placed in an oil bath at 180\\u0026deg;C, and 100 g of crushed PUF was continuously added, with mechanical stirring for 2 hours. Then, 20 g (175.4 mmol) of succinic acid (SA) was added, and the temperature was raised to 200\\u0026deg;C with mechanical stirring for another 2 hours. After the reaction was completed and the mixture was cooled to room temperature, the recovered polyol (RP) was obtained.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eRe-foaming experiment of recycled polyol\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eFlexible rigid polyurethane re-foaming.\\u003c/strong\\u003e Take X g of recovered polyol (RP), (100-X) g of virgin polyol (VP), 3.2 g of H\\u003csub\\u003e2\\u003c/sub\\u003eO, 0.8 g of silicone oil, 0.05 g of triethylamine, 0.2 g of diethanolamine, and 0.14 g of stannous octanoate and place them in a plastic beaker. Use a high-speed stirring plate to stir at 2000 rpm for 20 s until a uniform dispersion is formed; Take 46 g TDI and add it to the dispersion solution. Continue to use the high-speed stirring plate to stir at 2000 rpm for 10 seconds, and then quickly pour the mixture into the mold for molding. After the foaming height no longer changes, move it into an oven at 70 \\u003csup\\u003eo\\u003c/sup\\u003eC and take it out after curing for 22 hours to obtain RPUF-XRP. X represents the replacement amount of RP.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eHard segment treatment and rigid polyurethane re-foaming.\\u0026nbsp;\\u003c/strong\\u003eThe procedure involved pre-crushing hard segments to \\u0026le;500 \\u0026mu;m particles, followed by ball milling 100 g PPG5623 with X g of the crushed segments in a planetary mill (720 rpm, 6\\u0026ndash;8 h) to produce a homogeneous XHS%/PPG composite. Subsequently, 100 + X g of the XHS%/PPG was combined with 100 g polyether polyol (JB-635C), 4 g triethanolamine, 0.5 g dibutyltin dilaurate, 2 g H₂O, and 4 g silicone oil in a plastic beaker, homogenized at 2000 rpm for 20 s. After adding 108.8 g PAPI under continuous stirring (2000 rpm, 10 s), the mixture was immediately transferred to a mold. After the foaming height no longer changes, move it into an oven at 70 \\u003csup\\u003eo\\u003c/sup\\u003eC and take it out after curing for 22 hours to obtain rigid RPUF-XHS.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCharacterization methods for polyols\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAcid value (AV).\\u0026nbsp;\\u003c/strong\\u003eThe acid value (AV) was determined in accordance with the ASTM D4662-08 standard. Approximately 2 g of polyol was dispersed in 50 mL of ethanol in a 100 mL Erlenmeyer flask. Titrations were conducted using 0.1 N NaOH solution and the end point determined using a digital pH meter (HI 2211 pH/ORP\\u0026minus;Hanna Instruments), equipped with a HI 1043B probe. The AV was calculated using equation 1.\\u003c/p\\u003e\\n\\u003cp\\u003eAV=(A\\u0026minus;B) \\u0026times;56.1\\u0026times;N/W \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; (1)\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003ewhere A is the volume of NaOH solution required for the titration of the sample (mL); B is the volume of NaOH solution required for the titration of the blank (mL); N is the normality of the NaOH solution; and W is the weight of the sample (g).\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eHydroxyl number (HV).\\u0026nbsp;\\u003c/strong\\u003eThe hydroxyl number (HV) was determined in accordance with the ASTM D4274-05 standard in which the esterification process is catalyzed by imidazole. Titrations were conducted using 0.5 N NaOH solution. The HV was corrected taking into account the AV and calculated according to equation 2.\\u003c/p\\u003e\\n\\u003cp\\u003eHV= ((A\\u0026minus; B) \\u0026times;56.1\\u0026times;N)/W+ AV \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp;(2)\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003eWhere A is the volume of NaOH solution required for the titration of the sample (mL); B is the volume of NaOH solution required for the titration of the blank (mL); N is the normality of the NaOH solution; W is the weight of the sample (g); and AV is the acid value of the sample (mg KOH/g).\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eViscosity.\\u0026nbsp;\\u003c/strong\\u003eAccording to \\u0026quot;GB/T12008.7-2010\\u0026quot; viscosity testing method, the viscosity of polyol was measured with \\u0026quot;NDJ-1B\\u0026quot; rotary viscometer at 25 \\u003csup\\u003eo\\u003c/sup\\u003eC, and the specific operation steps were as follows: Pour a certain amount of recovered polyol sample into a container, put it into a constant temperature water bath at 25\\u003csup\\u003e\\u0026nbsp;o\\u003c/sup\\u003eC and stir. When the sample temperature is 25\\u003csup\\u003e\\u0026nbsp;o\\u003c/sup\\u003eC, select a suitable range of rotary viscometer rotor to immerse in the solution to be measured, and start the rotary viscometer with the standard scale line flush with the liquid level. Record the viscosity of the sample after the indication of the rotary viscometer is stable.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCharacterization methods for RPUF\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eDensity.\\u0026nbsp;\\u003c/strong\\u003eThe density of samples was tested by GB/T 10802-2006. According to GB/T 6342-1996, the length and width of the sample were measured by a tape measure with the minimum division value of 1 mm. Measure the thickness of the sample with a measuring tool with an accuracy of 0.1 mm, and start measuring at a distance of 30 mm from the edge of the sample, with no less than 5 measuring points and even intervals.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eRebound rate.\\u0026nbsp;\\u003c/strong\\u003eThe resilience of samples was tested by GB/T 10802-2006. According to GB/T 6670-1997, the sample size is (100\\u0026plusmn; 3) mm\\u0026times; (100\\u0026plusmn; 3) mm\\u0026times; (50\\u0026plusmn; 2) mm, and the number of samples is 3.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eindentation force deflection.\\u0026nbsp;\\u003c/strong\\u003eGB/T 10802-2006 was used to test the indentation performance of the samples. According to method B specified in GB/T 10807-2006, the sample size is (380\\u0026plusmn; 20) mm\\u0026times; (380\\u0026plusmn; 20) mm\\u0026times; (50\\u0026plusmn; 2) mm, and the number of samples is three.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003epermanent compression rate.\\u0026nbsp;\\u003c/strong\\u003eGB/T 10802-2006 was used to test the compression set rate of samples. According to the method A specified in GB/T 6669-2001, the test temperature is 70\\u0026plusmn; 2 ℃, the test time is 22 h, the thickness of the sample is compressed to 25% of the original thickness, and the sample size is (50\\u0026plusmn; 1) mm\\u0026times; (50\\u0026plusmn; 1) mm\\u0026times; (25\\u0026plusmn; 1) mm.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eShore C Hardness.\\u0026nbsp;\\u003c/strong\\u003eThe hardness of the sample was tested by Hg/T 2489-1993 standard. According to the method specified in Hg/T 2489-1993, the sample thickness is (10\\u0026plusmn; 5) mm.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCompressive properties.\\u0026nbsp;\\u003c/strong\\u003eThe compressive properties of samples were tested by GB/T 8813-2020 standard. According to the method A specified in GB/T 8813-2020, the thickness of the sample is (50\\u0026plusmn; 1)mm, and the compression surface of the sample is (50\\u0026plusmn; 1) mm\\u0026times; (50\\u0026plusmn; 1) mm.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCalculation of environmental energy impact\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eTo assess the sustainability of comparable methodologies, we employed the tripartite evaluation framework developed by Thielemans\\u0026nbsp;et al. and Zhang et al.\\u003csup\\u003e28,29\\u003c/sup\\u003e, incorporating energy efficiency metrics (\\u0026epsilon;), environmental impact factor (E), and combined environmental-energy impact (\\u0026xi;). A normalized energy economy metric (\\u0026epsilon;) was introduced to facilitate systematic comparison of process variables including reaction temperature, catalyst selection, and material ratios. This metric is mathematically defined as:\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cimg src=\\\"data:image/png;base64,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\\\" width=\\\"87\\\" height=\\\"52\\\"\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003ewhere Y represents the mass yield of monomers, T denotes reaction temperature (\\u0026deg;C), and t indicates reaction duration (min). The environmental factor (E) was refined from conventional mass intensity calculations to explicitly account for waste generation across material inputs. Finally, the composite parameter \\u0026xi; integrates both energy and material efficiency through:\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cimg 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\\\" width=\\\"654\\\" height=\\\"92\\\"\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eIdeal catalytic systems are characterized by maximized \\u0026epsilon; values alongside minimized E and \\u0026xi;, reflecting optimal energy utilization with minimal ecological burden.\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003eAcknowledgements\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThis work was supported by the Key Research Program of Zhejiang (2021C01087), the National Natural Science Foundation of China (51773180, 52273094, 52003237, 21875009), “Pioneer” R\\u0026amp;D Program of Zhejiang (2023C01083) and the Fundamental Research Funds for the Provincial Universities of Zhejiang (2021C01087, 2021C01125), Zhejiang University Students' Science and Technology Innovation Activity Plan (New Miao Talents Plan) (G23131250069).\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCompeting interests\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe authors declare no competing interests.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\n\\u003cli\\u003eChristensen, P. 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Scr.\\u003c/em\\u003e\\u003cstrong\\u003eT115\\u003c/strong\\u003e, 232-234 (2005).\\u003c/li\\u003e\\n\\u003c/ol\\u003e\"}],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":true,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":true,\"hideJournal\":false,\"highlight\":\"\",\"institution\":\"\",\"isAcceptedByJournal\":false,\"isAuthorSuppliedPdf\":false,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":false,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"nature-portfolio\",\"isNatureJournal\":true,\"hasQc\":false,\"allowDirectSubmit\":false,\"externalIdentity\":\"\",\"sideBox\":\"\",\"snPcode\":\"\",\"submissionUrl\":\"\",\"title\":\"Nature Portfolio\",\"twitterHandle\":\"\",\"acdcEnabled\":false,\"dfaEnabled\":false,\"editorialSystem\":\"ejp\",\"reportingPortfolio\":\"\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":false},\"keywords\":\"\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-6709291/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-6709291/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eThe development of efficient catalytic systems for polyurethane foam (PUF) recycling under mild conditions remains a critical challenge in achieving sustainable plastic circularity. Here, we report a ternary catalyst (TMG/Cd/HMMI) featuring a bimetallic Cd(II) center coordinated with 1,1,3,3-tetramethylguanidine (TMG) and 1-methyl-2-hydroxymethylimidazole (HMMI), which synergistically enhances the depolymerization of PUF. Integrated with a multi-stage degradation strategy, the catalyst efficiently catalyzes the degradation of carbamate and urea bonds in PUF under mild conditions (180 – 200 °C, 4 h, 10 wt% degradation agent relative to PUF mass), enabling spontaneous phase separation into high-purity recycled polyols (RP) and isocyanate-derived hard segments (HS) without requiring purification. The RP exhibit near-identical properties to virgin polyols and can substitute up to 40 wt% in new foam synthesis without compromising mechanical performance. Meanwhile, the hard segment can be reused as a reinforcing additive of rigid foam. This approach ensures full resource recovery, aligning with circular economy principles.\\u003c/p\\u003e\",\"manuscriptTitle\":\"Synergistic Bimetallic Catalysis for Closed-Loop Polyurethane Foam Upcycling via Proximity-Driven Depolymerization\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2025-06-25 09:22:43\",\"doi\":\"10.21203/rs.3.rs-6709291/v1\",\"editorialEvents\":[],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"nature-communications\",\"isNatureJournal\":true,\"hasQc\":false,\"allowDirectSubmit\":false,\"externalIdentity\":\"NCOMMS\",\"sideBox\":\"Learn more about [Nature Communications](http://www.nature.com/ncomms/)\",\"snPcode\":\"\",\"submissionUrl\":\"https://mts-ncomms.nature.com/\",\"title\":\"Nature Communications\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"ejp\",\"reportingPortfolio\":\"Nature Communications\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":false}}],\"origin\":\"\",\"ownerIdentity\":\"372bd124-20ef-44e9-ba7d-38b472d33b2f\",\"owner\":[],\"postedDate\":\"June 25th, 2025\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"under-review\",\"subjectAreas\":[{\"id\":49748813,\"name\":\"Physical sciences/Chemistry/Green chemistry/Sustainability\"},{\"id\":49748814,\"name\":\"Scientific community and society/Business and industry/Engineering/Chemical engineering\"},{\"id\":49748815,\"name\":\"Physical sciences/Chemistry/Catalysis/Catalytic mechanisms\"},{\"id\":49748816,\"name\":\"Physical sciences/Chemistry/Polymer chemistry/Polymer synthesis\"}],\"tags\":[],\"updatedAt\":\"2025-06-25T09:22:43+00:00\",\"versionOfRecord\":[],\"versionCreatedAt\":\"2025-06-25 09:22:43\",\"video\":\"\",\"vorDoi\":\"\",\"vorDoiUrl\":\"\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-6709291\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-6709291\",\"identity\":\"rs-6709291\",\"version\":[\"v1\"]},\"buildId\":\"8U1c8b4HqxoKbykW_rLl7\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}