Facile recovery of terephthalic acid from PET bottles via acid hydrolysis with nitric acid and applications in synthesis of cobalt MOFs

Facile recovery of terephthalic acid from PET bottles via acid hydrolysis with nitric acid and applications in synthesis of cobalt MOFs | 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 Research Article Facile recovery of terephthalic acid from PET bottles via acid hydrolysis with nitric acid and applications in synthesis of cobalt MOFs Victor Seabra, João M. R. Gonçalves, Ana L. S. Moura, Vinícius G. Luna, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4631763/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 16 Sep, 2024 Read the published version in Transition Metal Chemistry → Version 1 posted 15 You are reading this latest preprint version Abstract Poly(ethylene terephthalate) (PET) taken from postconsumer commercial water bottles was subjected to acid hydrolysis with HNO₃ to recover terephthalic acid (H₂TPA). The H₂TPA was submitted to mono-nitration with HNO₃/H 2 SO 4 to produce 2-nitro-terephthalic acid (NO₂-H₂TPA) in good yield. Both compounds were well characterized by NMR (¹H; ¹³C; ¹H-¹³C HSQC). These two molecules were used as ligands for the syntheses of two new cobalt-based Metal-Organic Frameworks (MOFs) via solvothermal methodology, in dimethylformamide (DMF) or dimethylacetamide (DMA). The MOFs Co-TPA-DMA (1) and Co-(NO₂-TPA)-DMF (2) were obtained and characterized by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). pet bottles recycling terephtalic acid nitro-terephtalic acid metal organic framework cobalt Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction Metal-Organic Frameworks (MOFs) are coordination polymers consisting of metal ions or metal clusters coordinated to organic ligand as linkers, mainly to form two- or three-dimensional structures [ 1 ]. Usually, the ordered structure is crystalline, with high surface area [ 2 ]. The structure arrangements create pores and adjustable properties that allows a wide range of applications [ 3 ], such as photocatalysis [ 3 – 5 ], small molecule storage and separation and separation [ 6 – 8 ], drug delivery[ 9 – 11 ], chemical sensing and others [ 12 ]. MOF is obtained by combine a certain transition metal ion (M) with an appropriate ligand (L) that allows the polymerization to be aligned as the model - M-L-M-L-, to result in a well-organized and stable structure. Accordingly, N-pyridines functionalized with other binding sites [ 13 ], imidazolate ions [ 14 ] and carboxylate ions are usual as metal ion linkers. In this last type of organic compound, trimesic acid (benzene-1,3,5-tricarboxylic acid) and terephthalic acid (benzene-1,4-dicarboxylic acid; H 2 TPA) are well used with dicationic metal ions of the first transition series [ 15 ], following classical Werner coordination compounds. Green synthesis methods for obtaining MOFs have gained prominence, aiming to reduce solvent consumption and waste production [ 16 ]. Another approach is the synthesis of MOFs from compounds originating from materials considered waste, that is, carrying out chemical recycling to obtain a reagent and then a new product; in this case, a MOF. In this regard, PET (polyethylene terephthalate) bottles are a source of H 2 TPA [ 17 , 18 ]. To obtain this acid from PET, it is necessary to perform a hydrolysis process, usually carried out in an alkaline medium, a process that requires time and reagent consumption [ 19 ]. However, in the present study, it was developed a new acid hydrolysis process using nitric acid that transforms PET into H 2 TPA in a quick, simple, and low-cost reaction. Thus, it is demonstrated the syntheses of MOFs of cobalt(II) ions from recovered H 2 TPA. Additionally, the obtained acid was functionalized with a nitro group by replacing one aromatic hydrogen atom to produce NO 2 -H 2 TPA, which was used in synthesis of Co-MOF with a new network [ 20 ]. In this study, crystalline structures of Co-MOFs were obtained from solvothermal method, as it is usual in literature [ 21 ], under well-controlled conditions of temperature and reaction time. Moreover, to obtain well-defined MOFs, it is ideally required to use an appropriate solvent to dissolve both the organic ligand and the precursor metal salt. Thus, in this study was also investigated the use of the N,N-disubstituted amides dimethylacetamide (NMe 2 (CHO); DMA) and dimethylformamide (NMe 2 (CMeO); DMF). They have high boiling points (> 150°C), suitable for solvothermal processes, but they differ in the carbonyl moiety, providing a different π-donating nature in the N atoms that are capable of coordinating as a strong base and perhaps participating as ligands in MOF structures. The obtained acid compounds were characterized by NMR and the MOFs by X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. The present article brings together novel H 2 TPA extraction methodology from commercial PET bottles and procedures designed to produce MOFs. This approach presents a chemical recycling pathway for PET bottles while also offering an economically attractive route for MOF manufacturing. Experimental 2.1 Physical Measurements and Reagents Materials and methods The solvents N , N ’-dimethylformamide (DMF) and N , N ’-dimethylacetamide (DMA), Nitric Acid 65%, sulphuric acid 95.0–98.0%, as well as the precursor salt CoCl₂∙6H₂O, were obtained from Sigma-Aldrich and used as received. Fourier-Transform Infrared (FTIR) spectra were measured on Shimadzu IR Affinity 1 FTIR spectrometer with KBr pellets, scanning from 4000 to 400 cm‾¹ at room temperature. The Nuclear Magnetic Resonance (NMR) ¹H and ¹³C{ 1 H} spectra were obtained in DMSO d₆ ampoule obtained of Sigma-Aldrich at 25.0°C on an Agilent MR 500 Ultra shield spectrometer operating at 500.13 and 125.61 MHz, respectively. The morphology of the prepared materials was studied by using a scanning electron microscope (JEOL JSM 7200 F), equipped with a Bruker XFlash 6–60 (60 mm²) EDS system. Single Crystal X-ray Diffraction – SCXRD SCXRD data for both compounds were collected using an XTALab Synergy-S Dualflex Rigaku diffractometer equipped with Mo Kα (0.71073 Å) and Cu Kα (1.54184 Å) radiation at 100 K. The structures were determined using the intrinsic phasing method implemented in the SHELXT-2018/2 software [ 22 ], and subsequently refined employing the least-squares method with SHELXL-2019, [ 23 ] both integrated within the Olex2 software platform. [ 24 ] All non-hydrogen atoms were refined anisotropically, while hydrogen atoms were refined isotropically and had their positions idealized using the riding model. [ 18 ] Both the measured crystals were non-merohedral twin, being refined with twin law 0.0 0.0–1.0 | 0.0–1.0 0.0 | -1.0 0.0 0.0 and BASF factor of 0.201(2) for 1 , and twin law − 1.0–1.0 0.0 | 0.0 1.0 0.0 | 0.0 0.0–1.0 and BASF factor of 0.322(1) for 2 . Crystallographic parameters tables, bond angles, distances, and intermolecular interactions were computed using Olex2, while structural representations were generated using Mercury 4.0 [ 25 ]. Hirshfeld Surface analysis and 2D fingerprint plots were generated using Crystal Explorer 21.0 [ 26 ]. Table 1 summarizes some information about the data collection and refinement of the structures. The CIF file of 1 and 2 were deposited in the Cambridge Structural Database with CCDC numbers of 2353874 and 2353875, respectively. Copies of the data can be accessed, free of charge, via www.ccdc.ac.uk . Table 1 Crystallographic data and structure refinement for MOFs Identification code Co-TPA-DMA (1) Co-NO₂-TPA-DMF (2) Empirical formula C₄₀H₄₈Co₃N₄O₁₆ C₈H₉CoN₂O₆ Formula weight 1017.61 281.10 Temperature/K 99.99(13) 100.00(10) Crystal system monoclinic trigonal Space group \({\text{P}}_{\text{n}}\) \(\text{P}\stackrel{-}{3}\) a/Å 15.4551(4) 16.00871(13) b/Å 9.7493(2) 16.00871(13) c/Å 15.5236(5) 7.63143(7) β/° 108.528(3) 90 Volume/Å 2217.80(11) 1693.75(3) Z 2 6 ρcalcg/cm 1.524 1.654 µ/mm 1.183 12.118 F(000) 1050.0 855.0 Absorption correction Multi-scan Multi-scan T min /T max 0.771/1.000 0.574/1.000 Crystal size/mm 0.131 × 0.106 × 0.022 0.149 × 0.108 × 0.102 Radiation Mo Kα (λ = 0.71073) Cu Kα (λ = 1.54184) 2Θ range for data collection/° 5.012 to 68.12 11.054 to 140.076 Index ranges -22 ≤ h ≤ 24 -14 ≤ k ≤ 15 -23 ≤ l ≤ 22 -19 ≤ h ≤ 19 -18 ≤ k ≤ 17 -9 ≤ l ≤ 9 Reflections collected 37574 11935 Independent reflections 13818 [R int = 0.0518] 2145 [R int = 0.0735] Data/restraints/parameters 13818/2/575 2145/0/166 Goodness-of-fit on F 1.034 1.057 Final R indexes [I ≥ 2σ(I)] R 1 = 0.0718, wR 2 = 0.1923 R 1 = 0.0331, wR 2 = 0.0865 Largest diff. peak/hole / e Å 1.79/-0.78 0.31/-0.56 The morphologies of the materials were studied by using a Field Emission Scanning Electronic Microscopy (FESEM) (JEOL JSM 7200 F), equipped with a Bruker XFlash 6/60 (60 mm²) EDS system equipped with software Esprit 2. The samples were coated with carbon using a Coating System BAL-TEC MED 020 (BAL-TEC, Liechtenstein) and kept in a desiccator until analysis. Conditions: chamber pressure = 2.00x10⁻² mbar; current = 60mA; deposition rate 0.60nm/s. For the EDS a Co standard was used for calibration, with an electron beam of 10kV for DMA for Co-TPA-DMA ( 1 ) and 5 kV for Co-NO₂-TPA-DMF ( 2) with a focal distance of 10 µm. 2.2 Obtaining the terephthalic acid from PET bottles and synthesis of 2-nitro-terephtalic acid Terephthalic acid (benzene-1,4-dicarboxylate acid; H₂TPA) was isolated from PET bottles used in commercial bottled waters, via acid hydrolysis. Small flakes (~ 1 cm 2 ) of plastic bottle (30 g) and concentrated HNO₃ (68%; 150 mL) were added in a flask. The mixture was refluxed at 140°C for 30 min. A white solid was formed with simultaneous evolution of NO₂ gas. The solid was filtered in Buchner funnel, washed with water until neutral pH value and dried in vacuum (96% yield). The other component of PET, ethylene glycol, is regenerated during this hydrolysis and is removed in the washing process due to its water solubility. The synthesis of 2-nitro-terephtlic acid (NO₂-H₂TPA) was via mono-nitration of 20 g H₂TPA, in a mixture of concentrated HNO₃ with H₂SO₄ in a 1:2 (v/v) ratio. The mixture was refluxed at 100°C for 8 h. A white solid was formed and filtered in Buchner funnel, washed with water until neutral pH value, recrystallized in acetone and in vacuum dried (85% yield). Syntheses of the MOFs with cobalt ion All the MOFs were produced following the same procedure. H₂TPA or NO 2 -H₂TPA (2 mmol) was dissolved in 15 mL of solvent (DMA or DMF) in a beaker, followed by addition of CoCl₂∙6H₂O (2 mmol). After the solution was homogenized, it was transferred to a solvothermal reactor and maintained under heating in an oven for 72 h. Violet crystals were collected in all the cases and washed with DMA for Co-TPA-DMA ( 1 ), or washed with DMF for Co-NO₂-TPA-DMF ( 2 ) and for Co-TPA-DMF ( 3 ). Results and Discussion 3.1 Characterization of Terephtalic Acid and 2-Nitro-Terephtalic Acid In the FTIR spectra of H₂BDC and NO₂-BDC (Fig S1 ), a prominent band in the range of 3200 − 3000 cm⁻ 1 , attributed to the νO-H stretch, was observed. The bands related to the stretches νC = O and νC-O appeared at 1681 and 1425 cm⁻ 1 , respectively, for H₂BDC, while for NO₂-BDC they appeared shifted to 1706 and 1416 cm − 1 . Vibration frequencies for the symmetric and asymmetric stretches of the nitro group (νNO₂) appeared in the region of 1541 and 1355 cm⁻ 1 for NO₂-BDC. Given the symmetry of the Terephthalic Acid (H₂TPA) molecule, the NMR spectra present two signals for hydrogen atoms and three signals for carbon atoms. In the ¹H NMR spectrum it is observed signals marked as A at 8.03 ppm (s; 4H) corresponding to the aromatic ring, and signals marked as B at 13.28 ppm (s; 2H) corresponding to a broad singlet typical of carboxylic acids (Fig S2a). In the ¹³C spectrum (Fig S2b), it is observed signal 1 at 129.91 ppm corresponding to carbons of aromatic ring linked to H, signal 2 at 134.91 ppm corresponding to carbons linked to COOH groups, and signal 3 representing the COOH groups themselves. The 2D HSQC ¹H-¹³C spectrum showed the correlation between H A and C 1 (Fig S1 c). In the mono-nitration reaction to form 2-Nitro-Terephthalic Acid (NO₂-TPA), the nitro group (NO₂) replaced one H group, disrupting the molecule symmetry compared to Terephthalic Acid. Hence, increasing the number of hydrogen atom environments to three aromatic ones, in addition to two more corresponding to COOH, appearing as a broad singlet at 13.84 ppm (Fig. 1 ). The carbons signals changes from three to eight, all of which were assigned according to the chemical environment, and the 2D HSQC ¹H-¹³C spectrum showed correlation with the respective hydrogen atoms. In the ¹H NMR spectrum, it is observed two doublet signals at 7.95 ppm labeled as A (d; 1H; J = 7.93 Hz), other at 8.28 ppm labeled as B (dd; 1H; J = 7,94 Hz) corresponding to the H atom on the opposite side of the NO₂ group, and signal at 8.38 labeled a C (d; 1H; J = 1.59 Hz) referring to the H adjacent to this same group. Additionally, it is not observed the signal at 8.03 ppm, indicating that the reaction and purification of 2-Nitro-Terephthalic Acid were successful. The broad singlet at 13.84 ppm refers to the hydrogen atoms of the COOH groups, which are more shielded in Terephthalic Acid and more unshielded in 2-Nitro-Terephthalic Acid. Additionally, 2-Nitro-Terephthalic Acid is more acidic than Terephthalic Acid. The ¹³C spectrum of 2-Nitro-Terephthalic Acid exhibits eight signals corresponding to the eight carbon atoms present in the molecule, each in a distinct chemical environment. Carbon atoms marked as 7 and 8 (at 166.05 ppm and 165.36 ppm, respectively) are associated with carboxylic acid (COOH) groups, with carbon 7 being more shielded, positioned ortho to the nitro group (NO₂), and carbon 8 in the para position. Next, carbon 2 , at 148.37 ppm, is observed, pertaining to the carbon attached to the nitro group itself, appearing more unshielded compared to other carbons in the ring due to the inductive effect of this group. Carbon atoms marked as 1 and 4 (at 134.64 ppm and 131.61 ppm) refer to atoms in the aromatic ring attached to the COOH groups, positioned para and meta , respectively. Finally, atoms marked as 5 , 6 , and 3 (at 134.11 ppm, 130.78 ppm, and 124.77 ppm) correspond to carbon atoms in the aromatic ring attached to hydrogen (H) groups in the para , meta , and ortho positions, respectively. These were assigned and differentiated using the 2D HSQC ¹H-¹³C spectrum, indicating correlations such as C 5 -H B , C 6 -H A , and C 3 -H C . It is observed that H C is the most deshielded due to the withdrawing inductive effect of the nitro group, while C 3 is the most shielded among the carbons with hydrogen substituents, possibly due to the difference in electronegativity between carbon and hydrogen. (Fig S3). Figure 1 . ¹H NMR spectra of 2-Nitro Terephtalic Acid in DMSO d₆ at 25.0°C. 3.2 Characterization of MOFs 3.2.1 Crystal Structures of Cobalt MOFs Cobalt MOFs can be formed by using di-alkyl- N -amides solvents, typically DMF and DMA, which possess characteristics such as high boiling points and the ability to dissolve both metal salts and organic molecules, allowing for a homogeneous mixture of these reagents and ensuring products with a high degree of purity. They undergo decomposition into alkylamines, in this case dimethylamine, usually occurring slowly at high temperatures, forming basic species that assist in the deprotonation of organic ligands such as carboxylic acids.[ 27 ] The presence of formate, derived from the decomposition of formamides in the presence of water, was observed in the structure of Co-NO₂-TPA-DMF (2) , and it is also capable of acting as a base by deprotonating ligands. Terephthalic acid, H₂TPA, falls into the category of carboxylate ligands, as it is this group that coordinates to the metal centers. It is also known that this group has a high chemical affinity with various metal centers, given the vast range of MOFs formed with different metals and these ligands in their structures. H₂TBC, sourced primarily from PET polymer, is highly versatile in its reactivity with different metals, and it has the capacity to be functionalized, as demonstrated in this work, where a simple nitration reaction was able to form a new ligand generating a new MOF structure. The synthesis of MOFs was carried out by conventional solvothermal method, capable of providing crystalline products with excellent quality, but with the drawback of long synthesis times, typically in the range of several days. Cobalt MOFs are formed by the direct coordination of carboxylate groups to the metals, where they can bind in different ways within the same structure (Fig. 3 ), including coordination of each oxygen atom to different metals (µ²-η¹:η¹, mode A), chelation to the same metal (η², mode B) and chelation to a first metal where another oxygen atom binds to a second metal (µ²-η²:η¹ mode C). These MOFs synthesized here do not exhibit SBUs (Secondary Building Units); as a consequence, various different coordination modes are observed within the same structure, and their stability is low, with metal leaching observed over time in aqueous solutions, outside the synthesis solvent, or when exposed to air. The solvothermal synthesis of compounds 1 (Co-TPA-DMA) and 2 (Co-NO₂-TPA-DMF) resulted in crystals suitable for single crystal X-ray diffraction technique. Compound 1 has an asymmetric unit composed of three distinct cobalt(II) cations with varying geometries (tetrahedral for Co1 and octahedral for Co2 and Co3), three coordinated BDC ligands, three coordinated DMA molecules, and one DMA solvent molecule as a guest, as shown in Fig. 4 a and 4 c. In contrast, the asymmetric unit of 2 contains only one cobalt(II) cation, which adopts an octahedral geometry, half of a NTPA 2− ligand ion, one formate ligand, and one coordinated DMA molecule (Fig. 4 b and 4 d). In compound 1 , Co2 and Co3 centers are coordinated by six oxygen atoms each. For Co3, two oxygen atoms originate from two DMA molecules, two from TPA 2− ligands in mode A, and the remaining two ligands derive from bridged oxygens in mode C. On the other hand, for the Co2 center, all the six oxygen ligands are originated from the TPA 2− ligands: four from the ligand in mode A, one bridged from mode C, and one bridged from mode E. The last one cobalt center Co1 is coordinated by four ligands, with one oxygen from a DMA molecule and the other three from the TPAC 2− ligand, where two are coordinated in mode A and one is in mode E. The combination of the cobalt(II) cations with the TPA 2− ligands and DMA molecules yielded a two-dimensional network with triangle-like cavities, as observed in Fig. 5 . In contrast, the analogous structure [ 28 ] reported in the literature features all crystallographic cobalt in octahedral geometry and exhibits coordination modes A, B, and C, with no solvent molecule coordinated to the metal center. Distortions in the coordination polyhedra of the cobalt(II) centers were observed in 1 , with the Co2 and Co3 centers showing bond angles involving the cis -positioned atoms with values that deviate from the idealized value of 90º expected for a perfect octahedral (Table S1 ). In the case of the tetrahedral cobalt, the τ 4 ' parameter was employed to confirm the geometry of the Co1 atom, which indicates a tetrahedral geometry when its value is close to one, and a square planar geometry when it is close to zero. [ 29 ] The τ 4 ' parameter calculated for Co1 is 0.769, suggesting a distorted tetrahedral geometry for this metal center. The mentioned distortions were caused mainly by the biting angle of the TPA 2− ions and the steric hindrance due to the arrangement of the ligands. Compound 2 has just one type of metal center, which exhibits an octahedral geometry and is coordinated to two oxygen atoms from two NO 2 -TPA 2− ions, three oxygens from formate ligands, and one oxygen from the DMF molecule. Differently from the observed for 1 , the NO 2 -TPA 2− ION is coordinated to the Co(II) cations only through the mode A. In the case of the formate ligand, it is attached to three Co(II) centers in the bridging µ 3 -η 1 :η 2 mode. It is interesting to observe the obtaining of clusters containing six cobalt(II) cations with the presence of the formate and the NO 2 -TPA 2− as bridging ligands, where the centers of these clusters coincide with the 3-fold rotoinversion axis (Fig. 6 ). The connection of the clusters occurs with the NO 2 -TPA 2− ligands, enabling the formation of a two-dimensional arrangement for 2 (Fig. 6 ). As observed in 1 , distortions from a regular octahedral geometry in the cobalt(II) center were also verified in 2 (Table S2). These distortions can be attributed to the presence of different ligands within the coordination sphere, as well as the coordination modes presented by the ligands. A positional disorder was verified in the nitro group of the NO 2 -TPA in 2 , with this group located at two different positions of the aromatic ring in a 1:1 ratio. Furthermore, even no formate salt or formic acid was used to synthesize the MOF, the formate ligand in the structure of 2 was originated by the decomposition of the DMF solvent in the reaction with water derived from the metallic salts. It is believed that these species are reaction intermediates that promote the deprotonation of ligands, transitioning from the form of carboxylic acid to carboxylate. With the comparison of both structures reported herein with similar cobalt(II) MOFs obtained with terephthalic acid in DMF and 2-nitroterephtalic acid in DMA that were reported previously [ 30 , 31 ], it can be easily verified the influence of the solvent in the construction of the MOFs. In 2013, Yang et al. [ 30 ] reported the characterization of Co(II) MOF with 2-nitroterephtalic acid, where the use of a mixture of DMF and water (10:3 ratio) yielded a three-dimensional MOF with the cobalt(II) cations coordinated just to the NO 2 -TPA ligand, showing water molecules as guest. Furthermore, it was demonstrated that the synthesis of a cobalt(II) MOF based on terephthalic acid using DMF as a solvent but at a different temperature resulted in an ionic three-dimensional MOF containing dimethylammonium as cations [ 31 ]. Another difference due to the synthetic route manifests in the intermolecular interactions observed within the crystal structure. However, only weak non-conventional hydrogen interactions, with the carbon atom as the donor, were observed for both compounds (Table S3). Through analysis of the Hirshfeld Surface (HS) and 2D fingerprint plots (FP), it has been determined that the presence of solvent molecules leads to distinct intermolecular interactions, contributing to the stabilization of the crystalline packing (see Figs. 7 and 8 ). The patterns observed in the fingerprint plots provide insights into the types of interactions present in the crystal. The bottom-right portion of the plot corresponds to the acceptor site, while the bottom-left corresponds to the donor site. As expected, the d norm HS of the asymmetric unit of the two MOFs have red regions, which corresponds mainly to the Co–O, C–O, and C–C bonds in 1 , and to the Co–O and C–C bonds in 2 . The FP of both structures show that the primary contributions are attributed to contacts involving hydrogen atoms (C⋯H/H⋯C, O⋯H/H⋯O, and H⋯H), while minor contributions include Co⋯O/O⋯Co, C⋯O/O⋯C, and C⋯C contacts (see Fig S4). The FP of 1 has spikes in the region of minor d i and d e values due to the presence of the Co–O, C–O, and C–C bonds to the formation of the two-dimensional structure. For 2 , the FP shows spikes with smaller d i and d e values, corresponding to the Co–O and C–C bonds. In 1 , the most significant contribution arises from H⋯H contacts (40.6%), aligning with the abundance of organic ligands in its asymmetric unit, while for 2 the predominant contribution is from O⋯H/H⋯O interactions (36%), likely due to the presence of nitro groups, which provide additional acceptor H-bond sites in the structure. This trend is similarly observed in CIFGUV [ 17 ]. Using the Pore Analyzer feature of the Mercury (version 2023.3.0) software, calculated diameters have been summarized in Table 2 . The values for all structures fall within the diameter range categorized as micropores. A discernible trend observed is that structures with DMA solvent exhibit slightly larger pore sizes compared to those with DMF solvent. Table 2 Pore sizes for all the structures. Sample Pore limiting diameter (Å) Maximum pore diameter (Å) Co-TPA-DMA (1) 1.09 2.19 VAKREG [ 31 ] 1.03 2.05 Co-NO₂-TPA-DMF (2) 1.31 2.61 CIFGUV [ 30 ] 2.29 3.73 3.2.3 Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) The morphology of Co-TPA-DMA and Co-NO₂-TPA-DMF is exhibited in Figs. 9 and 10 respectively. In both synthesized MOF, there is loss of crystallinity due to the removal of crystals from the solvents solution and the sample drying process, causing the loss of solvent coordinated in the crystalline lattice, destabilizing the crystal structure. The Co-TPA-DMA crystals do not have a regular shape (Fig. 9 ), making it impossible to obtain data on the length and calculate the area of the particles and exhibit an irregular surface texture (Fig. 9 b). The Co-NO₂-TPA-DMF feature one phase, a hexagonal prism shape (Fig. 10 ), with a particle size of ~ 1.5 µm x 3 µm with the clear pores. The elemental composition table of the MOFs obtained by EDS (Fig S5 an S6) reveals the presence of hydrogen, carbon, and nitrogen elements in the organic ligands and in the DMF and DMA solvents within the framework, in addition to the central metal cobalt and chlorine derived from the precursor salt (see Table 3 ). Table 3 Elemental composition of MOFs Co-TPA-DMA and Co-NO₂-TPA-DMF obtained via EDS. Co-TPA-DMA Element Mass (%) Mass Norm. (%) Atom (%) abs. Error (%) (3 sigma) Carbon 50.55 50.55 64.52 6.68 Oxygen 31.08 31.08 29.78 4.16 Chlorine 5.4 5.4 2.33 1.08 Cobalt 12.97 12.97 3.37 1.76 100 100 100 Co-NO ₂- TPA-DMF Element Mass (%) Mass Norm. (%) Atom (%) abs. Error (%) (3 sigma) Carbon 5.86 5.86 69.19 7.49 Oxygen 31.02 31.02 27.49 4.3 Chlorine 5.13 5.13 2.05 1.21 Cobalt 5.25 5.25 1.26 9.3 100 100 100 Conclusions In this work, it was obtained Terephthalic Acid, H₂TPA, recovered from PET bottles through acid hydrolysis using nitric acid via a simple and rapid reaction. Additionally, 2-Nitro-Terephthalic Acid, NO₂-TPA, was obtained through the mono-nitration of the recovered Terephthalic Acid, where both were characterized by FTIR and NMR spectroscopy including ¹H, ¹³C, and HSQC ¹H-¹³C. Both molecules were used as ligands in the synthesis of cobalt-based MOFs, using N , N ’-dimethylformamide (DMF) and N , N ’-dimethylacetamide (DMA) as solvents, via the solvothermal method, resulting in two new networks: Co-TPA-DMA (1) and Co-NO₂-TPA-DMF (2) , whose structures were elucidated by Single-Crystal X-ray diffraction (SCXRD) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). Declarations Supplementary Information The online version contains supplementary material available at (DOI do paper) Supplemental information available: NMR spectra. The CIF files of the structures were deposited in the Cambridge Structural Database with CCDC no. 2353874 and 2353875. Declaration of interest The authors declare no conflict of interest. Author contribution All experiments were performed and discussed by VS, JMRG, VGL and ALSM. Crystallographic data were obtained and discussed by PHOS and JAE. BSLN wrote the manuscript with some participation from the other authors. Funding Declaration The authors are grateful to the Brazilian funding agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq (Process numbers 308843/2021-3; 312505/2021-3), Coordination for the Improvement of Higher Education Personnel – Brazil (CAPES) – Financial Code 001 and Fundação de Amparo à Pesquisa do estado de São Paulo – FAPESP (Process numbers 2023/17102-2; 2017/15850-0, 2021/10066-5). References S.R. Batten, N.R. Champness, X.M. Chen, J. Garcia-Martinez, S. Kitagawa, L. Öhrström, M. O’Keeffe, M.P. Suh, J. Reedijk, Coordination polymers, metal-organic frameworks and the need for terminology guidelines, CrystEngComm 14 (2012) 3001–3004. https://doi.org/10.1039/c2ce06488j. H. Ji, S. Lee, J. Park, T. Kim, S. Choi, M. 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Arami-Niya, Enhancing energy carrier gas storage: Novel MOF-decorated carbons with high affinity toward methane and hydrogen, Chemical Engineering Research and Design 203 (2024) 419–430. https://doi.org/10.1016/j.cherd.2024.01.049. K. Nath, K.R. Wright, A. Ahmed, D.J. Siegel, A.J. Matzger, Adsorption of Natural Gas in Metal–Organic Frameworks: Selectivity, Cyclability, and Comparison to Methane Adsorption, J Am Chem Soc 146 (2024) 10517–10523. https://doi.org/10.1021/jacs.3c14535. Y. Li, Q. Guo, Z. Ding, H. Jiang, H. Yang, W. Du, Y. Zheng, K. Huo, L.L. Shaw, MOFs-Based Materials for Solid-State Hydrogen Storage: Strategies and Perspectives, Chemical Engineering Journal 485 (2024) 149665. https://doi.org/10.1016/j.cej.2024.149665. K. Kru̅kle-Be̅rziṇa, A. Lends, A. Boguszewska-Czubara, Cyclodextrin Metal–Organic Frameworks as a Drug Delivery System for Selected Active Pharmaceutical Ingredients, ACS Omega 9 (2024) 8874–8884. https://doi.org/10.1021/acsomega.3c06745. N. Yang, L. Wei, Y. 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Yurtcan, Zeolotic imidazolate frameworks (ZIFs) derived porous carbon: A review from crystal growth & green synthesis to oxygen reduction reaction activity, Int J Hydrogen Energy 46 (2021) 33782–33800. https://doi.org/10.1016/j.ijhydene.2021.07.196. M. Eddaoudi, H. Li, T. Reineke, M. Fehr, D. Kelley, T.L. Groy, O.M. Yaghi, Design and synthesis of metal-carboxylate frameworks with permanent microporosity, Top Catal 9 (1999) 105–111. https://doi.org/10.1023/a:1019110622091. S. Kumar, S. Jain, M. Nehra, N. Dilbaghi, G. Marrazza, K.-H. Kim, Green synthesis of metal–organic frameworks: A state-of-the-art review of potential environmental and medical applications, Coord Chem Rev 420 (2020) 213407. https://doi.org/10.1016/j.ccr.2020.213407. C.A. Harper, E.M. Petrie, Plastics Materials and Processes, 2003. https://doi.org/10.1002/0471459216. C. Chinglenthoiba, G. Mahadevan, J. Zuo, T. Prathyumnan, S. Valiyaveettil, Conversion of PET Bottle Waste into a Terephthalic Acid-Based Metal-Organic Framework for Removing Plastic Nanoparticles from Water, Nanomaterials 14 (2024) 257. https://doi.org/10.3390/nano14030257. L. Cosimbescu, D.R. Merkel, J. Darsell, G. Petrossian, Simple but Tricky: Investigations of Terephthalic Acid Purity Obtained from Mixed PET Waste, Ind Eng Chem Res 60 (2021) 12792–12797. https://doi.org/10.1021/acs.iecr.1c02604. E.F. Lange, R. Teranishi, B.E. Christensen, A sequence of synthesis in the general organic laboratory class, J Chem Educ 32 (1955) 40–41. https://doi.org/10.1021/ed032p40. C. Dey, T. Kundu, B.P. Biswal, A. Mallick, R. Banerjee, Crystalline metal-Organic frameworks (MOFs): Synthesis, structure and function, Acta Crystallogr B Struct Sci Cryst Eng Mater 70 (2014) 3–10. https://doi.org/10.1107/S2052520613029557. G.M. Sheldrick, SHELXT - Integrated space-group and crystal-structure determination, Acta Crystallographica Section A 71 (2015) 3–8. https://doi.org/10.1107/S2053273314026370. G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallographica Section C 71 (2015) 3–8. https://doi.org/10.1107/S2053229614024218. O. V Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, OLEX2: a complete structure solution, refinement and analysis program, J Appl Crystallogr 42 (2009) 339–341. https://doi.org/10.1107/S0021889808042726. C.F. MacRae, I. Sovago, S.J. Cottrell, P.T.A. Galek, P. McCabe, E. Pidcock, M. Platings, G.P. Shields, J.S. Stevens, M. Towler, P.A. Wood, Mercury 4.0: From visualization to analysis, design and prediction, J Appl Crystallogr 53 (2020) 226–235. https://doi.org/10.1107/S1600576719014092. P.R. Spackman, M.J. Turner, J.J. McKinnon, S.K. Wolff, D.J. Grimwood, D. Jayatilaka, M.A. Spackman, CrystalExplorer: A program for Hirshfeld surface analysis, visualization and quantitative analysis of molecular crystals, J Appl Crystallogr 54 (2021) 1006–1011. https://doi.org/10.1107/S1600576721002910. J. Muzart, N,N-Dimethylformamide: much more than a solvent, Tetrahedron 65 (2009) 8313–8323. https://doi.org/10.1016/j.tet.2009.06.091. X.F. Wang, Y.B. Zhang, W. Xue, X.L. Qi, X.M. Chen, Two temperature-induced isomers of metal-carboxylate frameworks based on different linear trinuclear Co3(RCOO)8 clusters exhibiting different magnetic behaviours, CrystEngComm 12 (2010) 3834–3839. https://doi.org/10.1039/c003032e. A. Okuniewski, D. Rosiak, J. Chojnacki, B. Becker, Coordination polymers and molecular structures among complexes of mercury(II) halides with selected 1-benzoylthioureas, Polyhedron 90 (2015) 47–57. https://doi.org/https://doi.org/10.1016/j.poly.2015.01.035. S.Y. Yang, H.B. Yuan, X. Bin Xu, R. Bin Huang, Influential factors on assembly of first-row transition metal coordination polymers, Inorganica Chim Acta 403 (2013) 53–62. https://doi.org/10.1016/j.ica.2013.03.042. X.F. Wang, Y.B. Zhang, W. Xue, X.L. Qi, X.M. Chen, Two temperature-induced isomers of metal-carboxylate frameworks based on different linear trinuclear Co3(RCOO)8 clusters exhibiting different magnetic behaviours, CrystEngComm 12 (2010) 3834–3839. https://doi.org/10.1039/c003032e. Additional Declarations No competing interests reported. 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Ellipsoids are represented with 50% of probability. Hydrogen atoms and guest solvent molecule in \u003cstrong\u003e1\u003c/strong\u003e were omitted for clarity.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/0f677da9cf2634ff444b8cbd.png"},{"id":60706411,"identity":"93ab6125-b5c7-4424-9d84-77f78c69d406","added_by":"auto","created_at":"2024-07-19 19:28:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":300121,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 5.\u003c/strong\u003e Two-dimensional network of \u003cstrong\u003e1\u003c/strong\u003e viewed through the [-101] direction (a) and coordination modes verified for the TPA\u003csup\u003e2-\u003c/sup\u003e ligand ions in \u003cstrong\u003e1\u003c/strong\u003e (b).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/3ea997dc446d4e360ebc4746.png"},{"id":60706414,"identity":"f3a65106-74ab-44ed-9e5d-233b855610da","added_by":"auto","created_at":"2024-07-19 19:28:46","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":231408,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 6.\u003c/strong\u003e Two-dimensional network of \u003cstrong\u003e2\u003c/strong\u003e viewed through the [001] direction (a) and coordination modes verified for the NO\u003csub\u003e2\u003c/sub\u003e-BDC\u003csup\u003e2-\u003c/sup\u003e and formate ligands in \u003cstrong\u003e2\u003c/strong\u003e (b).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/de9acf3f419ba43a981c45ac.png"},{"id":60706412,"identity":"f9993e09-102d-49bf-a7ad-e5ed9085ced6","added_by":"auto","created_at":"2024-07-19 19:28:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":834201,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 7. \u003c/strong\u003eHirshfeld surface and fingerprint plots of Co-TPA-DMA\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/7cd43250ec596a694ed00111.png"},{"id":60706417,"identity":"19c97b31-7fc8-4b48-bfd3-016e8d2bf0a6","added_by":"auto","created_at":"2024-07-19 19:28:47","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":817245,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 8\u003c/strong\u003e. Hirshfeld surface and fingerprint plots of Co-NO₂-TPA-DMF.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/a8c5175675408ebdab775638.png"},{"id":60706409,"identity":"d3deb314-ea26-4dcb-876e-40d7f1cf6e43","added_by":"auto","created_at":"2024-07-19 19:28:46","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":507060,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 9.\u003c/strong\u003e - Images obtained via SEM for the MOF Co-TPA-DMA. a) zoom times 160, b) zoom times 500.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/d42c485b89cfaf9f226063ea.png"},{"id":60706419,"identity":"f23176e5-861c-4066-9372-550fb330c470","added_by":"auto","created_at":"2024-07-19 19:28:47","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":478328,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 10\u003c/strong\u003e. Images collected via SEM. a) zoom times 1500, b) zoom times 6000 of the MOF Co-NO₂TPA-DMF.\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/1421efe02fbf14666c6e4b6a.png"},{"id":65104029,"identity":"9fb9ec6f-acb8-4a19-9964-e03ca2fac309","added_by":"auto","created_at":"2024-09-23 16:10:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4416364,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/7cb79a05-cffc-454f-8a82-9e7159366135.pdf"},{"id":60706418,"identity":"3dd9e4a3-1097-441d-a84d-ba9e8ea2d51f","added_by":"auto","created_at":"2024-07-19 19:28:47","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":13104479,"visible":true,"origin":"","legend":"","description":"","filename":"SuplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-4631763/v1/e01e3c030bebed764d413b4f.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Facile recovery of terephthalic acid from PET bottles via acid hydrolysis with nitric acid and applications in synthesis of cobalt MOFs","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMetal-Organic Frameworks (MOFs) are coordination polymers consisting of metal ions or metal clusters coordinated to organic ligand as linkers, mainly to form two- or three-dimensional structures [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Usually, the ordered structure is crystalline, with high surface area [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The structure arrangements create pores and adjustable properties that allows a wide range of applications [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], such as photocatalysis [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], small molecule storage and separation and separation [\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], drug delivery[\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], chemical sensing and others [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMOF is obtained by combine a certain transition metal ion (M) with an appropriate ligand (L) that allows the polymerization to be aligned as the model - M-L-M-L-, to result in a well-organized and stable structure. Accordingly, N-pyridines functionalized with other binding sites [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], imidazolate ions [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] and carboxylate ions are usual as metal ion linkers. In this last type of organic compound, trimesic acid (benzene-1,3,5-tricarboxylic acid) and terephthalic acid (benzene-1,4-dicarboxylic acid; H\u003csub\u003e2\u003c/sub\u003eTPA) are well used with dicationic metal ions of the first transition series [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], following classical Werner coordination compounds.\u003c/p\u003e \u003cp\u003eGreen synthesis methods for obtaining MOFs have gained prominence, aiming to reduce solvent consumption and waste production [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Another approach is the synthesis of MOFs from compounds originating from materials considered waste, that is, carrying out chemical recycling to obtain a reagent and then a new product; in this case, a MOF. In this regard, PET (polyethylene terephthalate) bottles are a source of H\u003csub\u003e2\u003c/sub\u003eTPA [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. To obtain this acid from PET, it is necessary to perform a hydrolysis process, usually carried out in an alkaline medium, a process that requires time and reagent consumption [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. However, in the present study, it was developed a new acid hydrolysis process using nitric acid that transforms PET into H\u003csub\u003e2\u003c/sub\u003eTPA in a quick, simple, and low-cost reaction. Thus, it is demonstrated the syntheses of MOFs of cobalt(II) ions from recovered H\u003csub\u003e2\u003c/sub\u003eTPA. Additionally, the obtained acid was functionalized with a nitro group by replacing one aromatic hydrogen atom to produce NO\u003csub\u003e2\u003c/sub\u003e-H\u003csub\u003e2\u003c/sub\u003eTPA, which was used in synthesis of Co-MOF with a new network [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this study, crystalline structures of Co-MOFs were obtained from solvothermal method, as it is usual in literature [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], under well-controlled conditions of temperature and reaction time. Moreover, to obtain well-defined MOFs, it is ideally required to use an appropriate solvent to dissolve both the organic ligand and the precursor metal salt. Thus, in this study was also investigated the use of the N,N-disubstituted amides dimethylacetamide (NMe\u003csub\u003e2\u003c/sub\u003e(CHO); DMA) and dimethylformamide (NMe\u003csub\u003e2\u003c/sub\u003e(CMeO); DMF). They have high boiling points (\u0026gt;\u0026thinsp;150\u0026deg;C), suitable for solvothermal processes, but they differ in the carbonyl moiety, providing a different π-donating nature in the N atoms that are capable of coordinating as a strong base and perhaps participating as ligands in MOF structures.\u003c/p\u003e \u003cp\u003eThe obtained acid compounds were characterized by NMR and the MOFs by X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy.\u003c/p\u003e \u003cp\u003eThe present article brings together novel H\u003csub\u003e2\u003c/sub\u003eTPA extraction methodology from commercial PET bottles and procedures designed to produce MOFs. This approach presents a chemical recycling pathway for PET bottles while also offering an economically attractive route for MOF manufacturing.\u003c/p\u003e"},{"header":"Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Physical Measurements and Reagents\u003c/h2\u003e\n \u003cp\u003e\u003cstrong\u003eMaterials and methods\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eThe solvents \u003cem\u003eN\u003c/em\u003e,\u003cem\u003eN\u003c/em\u003e\u0026rsquo;-dimethylformamide (DMF) and \u003cem\u003eN\u003c/em\u003e,\u003cem\u003eN\u003c/em\u003e\u0026rsquo;-dimethylacetamide (DMA), Nitric Acid 65%, sulphuric acid 95.0\u0026ndash;98.0%, as well as the precursor salt CoCl₂∙6H₂O, were obtained from Sigma-Aldrich and used as received. Fourier-Transform Infrared (FTIR) spectra were measured on Shimadzu IR Affinity 1 FTIR spectrometer with KBr pellets, scanning from 4000 to 400 cm\u0026oline;\u0026sup1; at room temperature. The Nuclear Magnetic Resonance (NMR) \u0026sup1;H and \u0026sup1;\u0026sup3;C{\u003csup\u003e1\u003c/sup\u003eH} spectra were obtained in DMSO d₆ ampoule obtained of Sigma-Aldrich at 25.0\u0026deg;C on an Agilent MR 500 Ultra shield spectrometer operating at 500.13 and 125.61 MHz, respectively. The morphology of the prepared materials was studied by using a scanning electron microscope (JEOL JSM 7200 F), equipped with a Bruker XFlash 6\u0026ndash;60 (60 mm\u0026sup2;) EDS system.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eSingle Crystal X-ray Diffraction \u0026ndash; SCXRD\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eSCXRD data for both compounds were collected using an XTALab Synergy-S Dualflex Rigaku diffractometer equipped with Mo K\u0026alpha; (0.71073 \u0026Aring;) and Cu K\u0026alpha; (1.54184 \u0026Aring;) radiation at 100 K. The structures were determined using the intrinsic phasing method implemented in the SHELXT-2018/2 software [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e], and subsequently refined employing the least-squares method with SHELXL-2019, [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e] both integrated within the Olex2 software platform. [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e] All non-hydrogen atoms were refined anisotropically, while hydrogen atoms were refined isotropically and had their positions idealized using the riding model. [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e] Both the measured crystals were non-merohedral twin, being refined with twin law 0.0 0.0\u0026ndash;1.0 | 0.0\u0026ndash;1.0 0.0 | -1.0 0.0 0.0 and BASF factor of 0.201(2) for \u003cstrong\u003e1\u003c/strong\u003e, and twin law \u0026minus;\u0026thinsp;1.0\u0026ndash;1.0 0.0 | 0.0 1.0 0.0 | 0.0 0.0\u0026ndash;1.0 and BASF factor of 0.322(1) for \u003cstrong\u003e2\u003c/strong\u003e. Crystallographic parameters tables, bond angles, distances, and intermolecular interactions were computed using Olex2, while structural representations were generated using Mercury 4.0 [\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e]. Hirshfeld Surface analysis and 2D fingerprint plots were generated using Crystal Explorer 21.0 [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e]. Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes some information about the data collection and refinement of the structures.\u003c/p\u003e\n \u003cp\u003eThe CIF file of \u003cstrong\u003e1\u003c/strong\u003e and \u003cstrong\u003e2\u003c/strong\u003e were deposited in the Cambridge Structural Database with CCDC numbers of 2353874 and 2353875, respectively. Copies of the data can be accessed, free of charge, via \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ewww.ccdc.ac.uk\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCrystallographic data and structure refinement for MOFs\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eIdentification code\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCo-TPA-DMA (1)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCo-NO₂-TPA-DMF (2)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEmpirical formula\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC₄₀H₄₈Co₃N₄O₁₆\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC₈H₉CoN₂O₆\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFormula weight\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1017.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e281.10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTemperature/K\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e99.99(13)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100.00(10)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCrystal system\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emonoclinic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003etrigonal\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSpace group\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{P}}_{\\text{n}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{P}\\stackrel{-}{3}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ea/\u0026Aring;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.4551(4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.00871(13)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eb/\u0026Aring;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.7493(2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.00871(13)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ec/\u0026Aring;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.5236(5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.63143(7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026beta;/\u0026deg;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e108.528(3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVolume/\u0026Aring;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2217.80(11)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1693.75(3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eZ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026rho;calcg/cm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.524\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.654\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026micro;/mm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.183\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.118\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF(000)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1050.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e855.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsorption correction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMulti-scan\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMulti-scan\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eT\u003csub\u003emin\u003c/sub\u003e/T\u003csub\u003emax\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.771/1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.574/1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCrystal size/mm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.131 \u0026times; 0.106 \u0026times; 0.022\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.149 \u0026times; 0.108 \u0026times; 0.102\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRadiation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMo K\u0026alpha; (\u0026lambda;\u0026thinsp;=\u0026thinsp;0.71073)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCu K\u0026alpha; (\u0026lambda;\u0026thinsp;=\u0026thinsp;1.54184)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u0026Theta; range for data collection/\u0026deg;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.012 to 68.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.054 to 140.076\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIndex ranges\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-22\u0026thinsp;\u0026le;\u0026thinsp;\u003cem\u003eh\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;24\u003c/p\u003e\n \u003cp\u003e-14\u0026thinsp;\u0026le;\u0026thinsp;\u003cem\u003ek\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;15\u003c/p\u003e\n \u003cp\u003e-23\u0026thinsp;\u0026le;\u0026thinsp;\u003cem\u003el\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-19\u0026thinsp;\u0026le;\u0026thinsp;\u003cem\u003eh\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;19\u003c/p\u003e\n \u003cp\u003e-18\u0026thinsp;\u0026le;\u0026thinsp;\u003cem\u003ek\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;17\u003c/p\u003e\n \u003cp\u003e-9\u0026thinsp;\u0026le;\u0026thinsp;\u003cem\u003el\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReflections collected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e37574\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11935\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIndependent reflections\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13818 [R\u003csub\u003eint\u003c/sub\u003e = 0.0518]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2145 [R\u003csub\u003eint\u003c/sub\u003e = 0.0735]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eData/restraints/parameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13818/2/575\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2145/0/166\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGoodness-of-fit on F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.034\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.057\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFinal R indexes [I\u0026thinsp;\u0026ge;\u0026thinsp;2\u0026sigma;(I)]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR\u003csub\u003e1\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.0718, wR\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.1923\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR\u003csub\u003e1\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.0331, wR\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.0865\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLargest diff. peak/hole / e \u0026Aring;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.79/-0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.31/-0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eThe morphologies of the materials were studied by using a Field Emission Scanning Electronic Microscopy (FESEM) (JEOL JSM 7200 F), equipped with a Bruker XFlash 6/60 (60 mm\u0026sup2;) EDS system equipped with software Esprit 2. The samples were coated with carbon using a Coating System BAL-TEC MED 020 (BAL-TEC, Liechtenstein) and kept in a desiccator until analysis. Conditions: chamber pressure\u0026thinsp;=\u0026thinsp;2.00x10⁻\u0026sup2; mbar; current\u0026thinsp;=\u0026thinsp;60mA; deposition rate 0.60nm/s. For the EDS a Co standard was used for calibration, with an electron beam of 10kV for DMA for Co-TPA-DMA (\u003cstrong\u003e1\u003c/strong\u003e) and 5 kV for Co-NO₂-TPA-DMF (\u003cstrong\u003e2)\u003c/strong\u003e with a focal distance of 10 \u0026micro;m.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e\u003cem\u003e2.2\u003c/em\u003e Obtaining the terephthalic acid from PET bottles and synthesis of 2-nitro-terephtalic acid\u003c/h2\u003e\n \u003cp\u003eTerephthalic acid (benzene-1,4-dicarboxylate acid; H₂TPA) was isolated from PET bottles used in commercial bottled waters, via acid hydrolysis. Small flakes (~\u0026thinsp;1 cm\u003csup\u003e2\u003c/sup\u003e) of plastic bottle (30 g) and concentrated HNO₃ (68%; 150 mL) were added in a flask. The mixture was refluxed at 140\u0026deg;C for 30 min. A white solid was formed with simultaneous evolution of NO₂ gas. The solid was filtered in Buchner funnel, washed with water until neutral pH value and dried in vacuum (96% yield). The other component of PET, ethylene glycol, is regenerated during this hydrolysis and is removed in the washing process due to its water solubility.\u003c/p\u003e\n \u003cp\u003eThe synthesis of 2-nitro-terephtlic acid (NO₂-H₂TPA) was via mono-nitration of 20 g H₂TPA, in a mixture of concentrated HNO₃ with H₂SO₄ in a 1:2 (v/v) ratio. The mixture was refluxed at 100\u0026deg;C for 8 h. A white solid was formed and filtered in Buchner funnel, washed with water until neutral pH value, recrystallized in acetone and in vacuum dried (85% yield).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eSyntheses of the MOFs with cobalt ion\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eAll the MOFs were produced following the same procedure. H₂TPA or NO\u003csub\u003e2\u003c/sub\u003e-H₂TPA (2 mmol) was dissolved in 15 mL of solvent (DMA or DMF) in a beaker, followed by addition of CoCl₂∙6H₂O (2 mmol). After the solution was homogenized, it was transferred to a solvothermal reactor and maintained under heating in an oven for 72 h. Violet crystals were collected in all the cases and washed with DMA for Co-TPA-DMA (\u003cstrong\u003e1\u003c/strong\u003e), or washed with DMF for Co-NO₂-TPA-DMF (\u003cstrong\u003e2\u003c/strong\u003e) and for Co-TPA-DMF (\u003cstrong\u003e3\u003c/strong\u003e).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results and Discussion","content":"\u003ch2\u003e3.1 Characterization of Terephtalic Acid and 2-Nitro-Terephtalic Acid\u003c/h2\u003e\u003cp\u003eIn the FTIR spectra of H₂BDC and NO₂-BDC (Fig \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), a prominent band in the range of 3200 − 3000 cm⁻\u003csup\u003e1\u003c/sup\u003e, attributed to the νO-H stretch, was observed. The bands related to the stretches νC = O and νC-O appeared at 1681 and 1425 cm⁻\u003csup\u003e1\u003c/sup\u003e, respectively, for H₂BDC, while for NO₂-BDC they appeared shifted to 1706 and 1416 cm\u003csup\u003e− 1\u003c/sup\u003e. Vibration frequencies for the symmetric and asymmetric stretches of the nitro group (νNO₂) appeared in the region of 1541 and 1355 cm⁻\u003csup\u003e1\u003c/sup\u003e for NO₂-BDC.\u003c/p\u003e\u003cp\u003eGiven the symmetry of the Terephthalic Acid (H₂TPA) molecule, the NMR spectra present two signals for hydrogen atoms and three signals for carbon atoms. In the ¹H NMR spectrum it is observed signals marked as \u003cb\u003eA\u003c/b\u003e at 8.03 ppm (s; 4H) corresponding to the aromatic ring, and signals marked as \u003cb\u003eB\u003c/b\u003e at 13.28 ppm (s; 2H) corresponding to a broad singlet typical of carboxylic acids (Fig S2a). In the ¹³C spectrum (Fig S2b), it is observed signal \u003cb\u003e1\u003c/b\u003e at 129.91 ppm corresponding to carbons of aromatic ring linked to H, signal \u003cb\u003e2\u003c/b\u003e at 134.91 ppm corresponding to carbons linked to COOH groups, and signal \u003cb\u003e3\u003c/b\u003e representing the COOH groups themselves. The 2D HSQC ¹H-¹³C spectrum showed the correlation between H\u003csub\u003e\u003cb\u003eA\u003c/b\u003e\u003c/sub\u003e and C\u003csub\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sub\u003e (Fig \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003ec).\u003c/p\u003e\u003cp\u003eIn the mono-nitration reaction to form 2-Nitro-Terephthalic Acid (NO₂-TPA), the nitro group (NO₂) replaced one H group, disrupting the molecule symmetry compared to Terephthalic Acid. Hence, increasing the number of hydrogen atom environments to three aromatic ones, in addition to two more corresponding to COOH, appearing as a broad singlet at 13.84 ppm (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The carbons signals changes from three to eight, all of which were assigned according to the chemical environment, and the 2D HSQC ¹H-¹³C spectrum showed correlation with the respective hydrogen atoms. In the ¹H NMR spectrum, it is observed two doublet signals at 7.95 ppm labeled as \u003cb\u003eA\u003c/b\u003e (d; 1H; J = 7.93 Hz), other at 8.28 ppm labeled as \u003cb\u003eB\u003c/b\u003e (dd; 1H; J = 7,94 Hz) corresponding to the H atom on the opposite side of the NO₂ group, and signal at 8.38 labeled a \u003cb\u003eC\u003c/b\u003e (d; 1H; J = 1.59 Hz) referring to the H adjacent to this same group. Additionally, it is not observed the signal at 8.03 ppm, indicating that the reaction and purification of 2-Nitro-Terephthalic Acid were successful. The broad singlet at 13.84 ppm refers to the hydrogen atoms of the COOH groups, which are more shielded in Terephthalic Acid and more unshielded in 2-Nitro-Terephthalic Acid.\u003c/p\u003e\u003cp\u003eAdditionally, 2-Nitro-Terephthalic Acid is more acidic than Terephthalic Acid. The ¹³C spectrum of 2-Nitro-Terephthalic Acid exhibits eight signals corresponding to the eight carbon atoms present in the molecule, each in a distinct chemical environment. Carbon atoms marked as \u003cb\u003e7\u003c/b\u003e and \u003cb\u003e8\u003c/b\u003e (at 166.05 ppm and 165.36 ppm, respectively) are associated with carboxylic acid (COOH) groups, with carbon \u003cb\u003e7\u003c/b\u003e being more shielded, positioned \u003cem\u003eortho\u003c/em\u003e to the nitro group (NO₂), and carbon \u003cb\u003e8\u003c/b\u003e in the \u003cem\u003epara\u003c/em\u003e position. Next, carbon \u003cb\u003e2\u003c/b\u003e, at 148.37 ppm, is observed, pertaining to the carbon attached to the nitro group itself, appearing more unshielded compared to other carbons in the ring due to the inductive effect of this group. Carbon atoms marked as \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e4\u003c/b\u003e (at 134.64 ppm and 131.61 ppm) refer to atoms in the aromatic ring attached to the COOH groups, positioned \u003cem\u003epara\u003c/em\u003e and \u003cem\u003emeta\u003c/em\u003e, respectively. Finally, atoms marked as \u003cb\u003e5\u003c/b\u003e, \u003cb\u003e6\u003c/b\u003e, and \u003cb\u003e3\u003c/b\u003e (at 134.11 ppm, 130.78 ppm, and 124.77 ppm) correspond to carbon atoms in the aromatic ring attached to hydrogen (H) groups in the \u003cem\u003epara\u003c/em\u003e, \u003cem\u003emeta\u003c/em\u003e, and \u003cem\u003eortho\u003c/em\u003e positions, respectively. These were assigned and differentiated using the 2D HSQC ¹H-¹³C spectrum, indicating correlations such as C\u003csub\u003e\u003cb\u003e5\u003c/b\u003e\u003c/sub\u003e-H\u003csub\u003e\u003cb\u003eB\u003c/b\u003e\u003c/sub\u003e, C\u003csub\u003e\u003cb\u003e6\u003c/b\u003e\u003c/sub\u003e-H\u003csub\u003e\u003cb\u003eA\u003c/b\u003e\u003c/sub\u003e, and C\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e-H\u003csub\u003e\u003cb\u003eC\u003c/b\u003e\u003c/sub\u003e. It is observed that H\u003csub\u003e\u003cb\u003eC\u003c/b\u003e\u003c/sub\u003e is the most deshielded due to the withdrawing inductive effect of the nitro group, while C\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e is the most shielded among the carbons with hydrogen substituents, possibly due to the difference in electronegativity between carbon and hydrogen. (Fig S3).\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e1\u003c/span\u003e. ¹H NMR spectra of 2-Nitro Terephtalic Acid in DMSO d₆ at 25.0°C.\u003c/p\u003e\u003ch2\u003e3.2 Characterization of MOFs\u003c/h2\u003e\u003ch2\u003e3.2.1 Crystal Structures of Cobalt MOFs\u003c/h2\u003e\u003cp\u003eCobalt MOFs can be formed by using di-alkyl-\u003cem\u003eN\u003c/em\u003e-amides solvents, typically DMF and DMA, which possess characteristics such as high boiling points and the ability to dissolve both metal salts and organic molecules, allowing for a homogeneous mixture of these reagents and ensuring products with a high degree of purity. They undergo decomposition into alkylamines, in this case dimethylamine, usually occurring slowly at high temperatures, forming basic species that assist in the deprotonation of organic ligands such as carboxylic acids.[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] The presence of formate, derived from the decomposition of formamides in the presence of water, was observed in the structure of Co-NO₂-TPA-DMF \u003cb\u003e(2)\u003c/b\u003e, and it is also capable of acting as a base by deprotonating ligands.\u003c/p\u003e\u003cp\u003eTerephthalic acid, H₂TPA, falls into the category of carboxylate ligands, as it is this group that coordinates to the metal centers. It is also known that this group has a high chemical affinity with various metal centers, given the vast range of MOFs formed with different metals and these ligands in their structures. H₂TBC, sourced primarily from PET polymer, is highly versatile in its reactivity with different metals, and it has the capacity to be functionalized, as demonstrated in this work, where a simple nitration reaction was able to form a new ligand generating a new MOF structure.\u003c/p\u003e\u003cp\u003eThe synthesis of MOFs was carried out by conventional solvothermal method, capable of providing crystalline products with excellent quality, but with the drawback of long synthesis times, typically in the range of several days. Cobalt MOFs are formed by the direct coordination of carboxylate groups to the metals, where they can bind in different ways within the same structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e3\u003c/span\u003e), including coordination of each oxygen atom to different metals (µ²-η¹:η¹, mode A), chelation to the same metal (η², mode B) and chelation to a first metal where another oxygen atom binds to a second metal (µ²-η²:η¹ mode C). These MOFs synthesized here do not exhibit SBUs (Secondary Building Units); as a consequence, various different coordination modes are observed within the same structure, and their stability is low, with metal leaching observed over time in aqueous solutions, outside the synthesis solvent, or when exposed to air.\u003c/p\u003e\u003cp\u003eThe solvothermal synthesis of compounds \u003cb\u003e1\u003c/b\u003e (Co-TPA-DMA) and \u003cb\u003e2\u003c/b\u003e (Co-NO₂-TPA-DMF) resulted in crystals suitable for single crystal X-ray diffraction technique. Compound \u003cb\u003e1\u003c/b\u003e has an asymmetric unit composed of three distinct cobalt(II) cations with varying geometries (tetrahedral for Co1 and octahedral for Co2 and Co3), three coordinated BDC ligands, three coordinated DMA molecules, and one DMA solvent molecule as a guest, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e4\u003c/span\u003ea and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e4\u003c/span\u003ec. In contrast, the asymmetric unit of \u003cb\u003e2\u003c/b\u003e contains only one cobalt(II) cation, which adopts an octahedral geometry, half of a NTPA\u003csup\u003e2−\u003c/sup\u003e ligand ion, one formate ligand, and one coordinated DMA molecule (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e4\u003c/span\u003eb and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e4\u003c/span\u003ed).\u003c/p\u003e\u003cp\u003eIn compound \u003cb\u003e1\u003c/b\u003e, Co2 and Co3 centers are coordinated by six oxygen atoms each. For Co3, two oxygen atoms originate from two DMA molecules, two from TPA\u003csup\u003e2−\u003c/sup\u003e ligands in mode A, and the remaining two ligands derive from bridged oxygens in mode C. On the other hand, for the Co2 center, all the six oxygen ligands are originated from the TPA\u003csup\u003e2−\u003c/sup\u003e ligands: four from the ligand in mode A, one bridged from mode C, and one bridged from mode E. The last one cobalt center Co1 is coordinated by four ligands, with one oxygen from a DMA molecule and the other three from the TPAC\u003csup\u003e2−\u003c/sup\u003e ligand, where two are coordinated in mode A and one is in mode E. The combination of the cobalt(II) cations with the TPA\u003csup\u003e2−\u003c/sup\u003e ligands and DMA molecules yielded a two-dimensional network with triangle-like cavities, as observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e5\u003c/span\u003e. In contrast, the analogous structure [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] reported in the literature features all crystallographic cobalt in octahedral geometry and exhibits coordination modes A, B, and C, with no solvent molecule coordinated to the metal center.\u003c/p\u003e\u003cp\u003eDistortions in the coordination polyhedra of the cobalt(II) centers were observed in \u003cb\u003e1\u003c/b\u003e, with the Co2 and Co3 centers showing bond angles involving the \u003cem\u003ecis\u003c/em\u003e-positioned atoms with values that deviate from the idealized value of 90º expected for a perfect octahedral (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). In the case of the tetrahedral cobalt, the τ\u003csub\u003e4\u003c/sub\u003e' parameter was employed to confirm the geometry of the Co1 atom, which indicates a tetrahedral geometry when its value is close to one, and a square planar geometry when it is close to zero. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] The τ\u003csub\u003e4\u003c/sub\u003e' parameter calculated for Co1 is 0.769, suggesting a distorted tetrahedral geometry for this metal center. The mentioned distortions were caused mainly by the biting angle of the TPA\u003csup\u003e2−\u003c/sup\u003e ions and the steric hindrance due to the arrangement of the ligands.\u003c/p\u003e\u003cp\u003eCompound \u003cb\u003e2\u003c/b\u003e has just one type of metal center, which exhibits an octahedral geometry and is coordinated to two oxygen atoms from two NO\u003csub\u003e2\u003c/sub\u003e-TPA\u003csup\u003e2−\u003c/sup\u003e ions, three oxygens from formate ligands, and one oxygen from the DMF molecule. Differently from the observed for \u003cb\u003e1\u003c/b\u003e, the NO\u003csub\u003e2\u003c/sub\u003e-TPA\u003csup\u003e2−\u003c/sup\u003e ION is coordinated to the Co(II) cations only through the mode A. In the case of the formate ligand, it is attached to three Co(II) centers in the bridging µ\u003csub\u003e3\u003c/sub\u003e-η\u003csup\u003e1\u003c/sup\u003e:η\u003csup\u003e2\u003c/sup\u003e mode. It is interesting to observe the obtaining of clusters containing six cobalt(II) cations with the presence of the formate and the NO\u003csub\u003e2\u003c/sub\u003e-TPA\u003csup\u003e2−\u003c/sup\u003e as bridging ligands, where the centers of these clusters coincide with the 3-fold rotoinversion axis (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The connection of the clusters occurs with the NO\u003csub\u003e2\u003c/sub\u003e-TPA\u003csup\u003e2−\u003c/sup\u003e ligands, enabling the formation of a two-dimensional arrangement for \u003cb\u003e2\u003c/b\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAs observed in \u003cb\u003e1\u003c/b\u003e, distortions from a regular octahedral geometry in the cobalt(II) center were also verified in \u003cb\u003e2\u003c/b\u003e (Table S2). These distortions can be attributed to the presence of different ligands within the coordination sphere, as well as the coordination modes presented by the ligands. A positional disorder was verified in the nitro group of the NO\u003csub\u003e2\u003c/sub\u003e-TPA in \u003cb\u003e2\u003c/b\u003e, with this group located at two different positions of the aromatic ring in a 1:1 ratio. Furthermore, even no formate salt or formic acid was used to synthesize the MOF, the formate ligand in the structure of \u003cb\u003e2\u003c/b\u003e was originated by the decomposition of the DMF solvent in the reaction with water derived from the metallic salts. It is believed that these species are reaction intermediates that promote the deprotonation of ligands, transitioning from the form of carboxylic acid to carboxylate.\u003c/p\u003e\u003cp\u003eWith the comparison of both structures reported herein with similar cobalt(II) MOFs obtained with terephthalic acid in DMF and 2-nitroterephtalic acid in DMA that were reported previously [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e], it can be easily verified the influence of the solvent in the construction of the MOFs. In 2013, Yang \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] reported the characterization of Co(II) MOF with 2-nitroterephtalic acid, where the use of a mixture of DMF and water (10:3 ratio) yielded a three-dimensional MOF with the cobalt(II) cations coordinated just to the NO\u003csub\u003e2\u003c/sub\u003e-TPA ligand, showing water molecules as guest. Furthermore, it was demonstrated that the synthesis of a cobalt(II) MOF based on terephthalic acid using DMF as a solvent but at a different temperature resulted in an ionic three-dimensional MOF containing dimethylammonium as cations [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Another difference due to the synthetic route manifests in the intermolecular interactions observed within the crystal structure. However, only weak non-conventional hydrogen interactions, with the carbon atom as the donor, were observed for both compounds (Table S3).\u003c/p\u003e\u003cp\u003eThrough analysis of the Hirshfeld Surface (HS) and 2D fingerprint plots (FP), it has been determined that the presence of solvent molecules leads to distinct intermolecular interactions, contributing to the stabilization of the crystalline packing (see Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e). The patterns observed in the fingerprint plots provide insights into the types of interactions present in the crystal. The bottom-right portion of the plot corresponds to the acceptor site, while the bottom-left corresponds to the donor site.\u003c/p\u003e\u003cp\u003eAs expected, the d\u003csub\u003enorm\u003c/sub\u003e HS of the asymmetric unit of the two MOFs have red regions, which corresponds mainly to the Co–O, C–O, and C–C bonds in \u003cb\u003e1\u003c/b\u003e, and to the Co–O and C–C bonds in \u003cb\u003e2\u003c/b\u003e. The FP of both structures show that the primary contributions are attributed to contacts involving hydrogen atoms (C⋯H/H⋯C, O⋯H/H⋯O, and H⋯H), while minor contributions include Co⋯O/O⋯Co, C⋯O/O⋯C, and C⋯C contacts (see Fig S4). The FP of \u003cb\u003e1\u003c/b\u003e has spikes in the region of minor d\u003csub\u003ei\u003c/sub\u003e and d\u003csub\u003ee\u003c/sub\u003e values due to the presence of the Co–O, C–O, and C–C bonds to the formation of the two-dimensional structure. For \u003cb\u003e2\u003c/b\u003e, the FP shows spikes with smaller d\u003csub\u003ei\u003c/sub\u003e and d\u003csub\u003ee\u003c/sub\u003e values, corresponding to the Co–O and C–C bonds. In \u003cb\u003e1\u003c/b\u003e, the most significant contribution arises from H⋯H contacts (40.6%), aligning with the abundance of organic ligands in its asymmetric unit, while for \u003cb\u003e2\u003c/b\u003e the predominant contribution is from O⋯H/H⋯O interactions (36%), likely due to the presence of nitro groups, which provide additional acceptor H-bond sites in the structure. This trend is similarly observed in CIFGUV [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003eUsing the Pore Analyzer feature of the Mercury (version 2023.3.0) software, calculated diameters have been summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The values for all structures fall within the diameter range categorized as micropores. A discernible trend observed is that structures with DMA solvent exhibit slightly larger pore sizes compared to those with DMF solvent.\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePore sizes for all the structures.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePore limiting diameter (Å)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMaximum pore diameter (Å)\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCo-TPA-DMA (1)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.09\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.19\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVAKREG [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.03\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.05\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCo-NO₂-TPA-DMF (2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.31\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.61\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCIFGUV [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.29\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.73\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003ch2\u003e3.2.3 Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS)\u003c/h2\u003e\u003cp\u003eThe morphology of Co-TPA-DMA and Co-NO₂-TPA-DMF is exhibited in Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e and \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e respectively. In both synthesized MOF, there is loss of crystallinity due to the removal of crystals from the solvents solution and the sample drying process, causing the loss of solvent coordinated in the crystalline lattice, destabilizing the crystal structure. The Co-TPA-DMA crystals do not have a regular shape (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e), making it impossible to obtain data on the length and calculate the area of the particles and exhibit an irregular surface texture (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003eb). The Co-NO₂-TPA-DMF feature one phase, a hexagonal prism shape (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e), with a particle size of ~ 1.5 µm x 3 µm with the clear pores. The elemental composition table of the MOFs obtained by EDS (Fig S5 an S6) reveals the presence of hydrogen, carbon, and nitrogen elements in the organic ligands and in the DMF and DMA solvents within the framework, in addition to the central metal cobalt and chlorine derived from the precursor salt (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cdiv class=\"gridtable\"\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=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eElemental composition of MOFs Co-TPA-DMA and Co-NO₂-TPA-DMF obtained via EDS.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCo-TPA-DMA\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMass (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMass Norm. (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAtom (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eabs. Error (%) (3 sigma)\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCarbon\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50.55\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50.55\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e64.52\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.68\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOxygen\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e31.08\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.08\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e29.78\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.16\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChlorine\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.33\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.08\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCobalt\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.97\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.97\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.37\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.76\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCo-NO\u003cem\u003e₂-\u003c/em\u003eTPA-DMF\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMass (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMass Norm. (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAtom (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eabs. Error (%) (3 sigma)\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCarbon\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.86\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.86\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e69.19\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.49\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOxygen\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e31.02\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.02\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27.49\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.3\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChlorine\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.13\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.13\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.05\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.21\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCobalt\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.25\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.25\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.26\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.3\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn this work, it was obtained Terephthalic Acid, H₂TPA, recovered from PET bottles through acid hydrolysis using nitric acid via a simple and rapid reaction. Additionally, 2-Nitro-Terephthalic Acid, NO₂-TPA, was obtained through the mono-nitration of the recovered Terephthalic Acid, where both were characterized by FTIR and NMR spectroscopy including \u0026sup1;H, \u0026sup1;\u0026sup3;C, and HSQC \u0026sup1;H-\u0026sup1;\u0026sup3;C. Both molecules were used as ligands in the synthesis of cobalt-based MOFs, using \u003cem\u003eN\u003c/em\u003e,\u003cem\u003eN\u003c/em\u003e\u0026rsquo;-dimethylformamide (DMF) and \u003cem\u003eN\u003c/em\u003e,\u003cem\u003eN\u003c/em\u003e\u0026rsquo;-dimethylacetamide (DMA) as solvents, via the solvothermal method, resulting in two new networks: Co-TPA-DMA \u003cb\u003e(1)\u003c/b\u003e and Co-NO₂-TPA-DMF \u003cb\u003e(2)\u003c/b\u003e, whose structures were elucidated by Single-Crystal X-ray diffraction (SCXRD) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS).\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eSupplementary Information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe online version contains supplementary material available at (DOI do paper)\u003c/p\u003e\n\u003cp\u003eSupplemental information available: \u0026nbsp; NMR spectra. The CIF files of the structures were deposited in the Cambridge Structural Database with CCDC no.\u0026nbsp;2353874 and 2353875.\u003c/p\u003e\n\u003cp\u003eDeclaration of interest\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll experiments were performed and discussed by VS,\u0026nbsp;JMRG, VGL and ALSM.\u0026nbsp;Crystallographic data were obtained and discussed by PHOS and JAE. \u0026nbsp;BSLN wrote the manuscript with some participation from the other authors.\u003c/p\u003e\n\u003cp\u003eFunding Declaration\u003c/p\u003e\n\u003cp\u003eThe authors are grateful to the Brazilian funding agencies Conselho Nacional de Desenvolvimento Cient\u0026iacute;fico e Tecnol\u0026oacute;gico \u0026ndash; CNPq (Process numbers 308843/2021-3; 312505/2021-3), Coordination for the Improvement of Higher Education Personnel \u0026ndash; Brazil (CAPES) \u0026ndash; Financial Code 001 and Funda\u0026ccedil;\u0026atilde;o de Amparo \u0026agrave; Pesquisa do estado de S\u0026atilde;o Paulo \u0026ndash; FAPESP (Process numbers 2023/17102-2; 2017/15850-0, 2021/10066-5).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eS.R. 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Chen, Two temperature-induced isomers of metal-carboxylate frameworks based on different linear trinuclear Co3(RCOO)8 clusters exhibiting different magnetic behaviours, CrystEngComm 12 (2010) 3834\u0026ndash;3839. https://doi.org/10.1039/c003032e.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"transition-metal-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"tmch","sideBox":"Learn more about [Transition Metal Chemistry](http://link.springer.com/journal/11243)","snPcode":"11243","submissionUrl":"https://submission.nature.com/new-submission/11243/3","title":"Transition Metal Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"pet bottles recycling, terephtalic acid, nitro-terephtalic acid, metal organic framework, cobalt","lastPublishedDoi":"10.21203/rs.3.rs-4631763/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4631763/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePoly(ethylene terephthalate) (PET) taken from postconsumer commercial water bottles was subjected to acid hydrolysis with HNO₃ to recover terephthalic acid (H₂TPA). The H₂TPA was submitted to mono-nitration with HNO₃/H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e to produce 2-nitro-terephthalic acid (NO₂-H₂TPA) in good yield. Both compounds were well characterized by NMR (\u0026sup1;H; \u0026sup1;\u0026sup3;C; \u0026sup1;H-\u0026sup1;\u0026sup3;C HSQC). These two molecules were used as ligands for the syntheses of two new cobalt-based Metal-Organic Frameworks (MOFs) via solvothermal methodology, in dimethylformamide (DMF) or dimethylacetamide (DMA). The MOFs Co-TPA-DMA \u003cb\u003e(1)\u003c/b\u003e and Co-(NO₂-TPA)-DMF \u003cb\u003e(2)\u003c/b\u003e were obtained and characterized by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS).\u003c/p\u003e","manuscriptTitle":"Facile recovery of terephthalic acid from PET bottles via acid hydrolysis with nitric acid and applications in synthesis of cobalt MOFs","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-19 19:28:41","doi":"10.21203/rs.3.rs-4631763/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-07-18T12:29:56+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-18T12:21:35+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-17T20:38:56+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-09T11:00:17+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-04T18:23:19+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-04T09:57:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"125728054488915833229002428606903218746","date":"2024-07-01T07:51:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"171877464489233869252008250300293163055","date":"2024-06-29T13:51:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"314494239869336035667383184584195117238","date":"2024-06-28T10:03:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"26013371486377173946306924547084374905","date":"2024-06-26T18:24:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"191196356397027709558733378909688729218","date":"2024-06-26T17:50:24+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-26T17:40:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-06-26T17:04:13+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-06-26T17:00:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Transition Metal Chemistry","date":"2024-06-24T17:32:05+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"transition-metal-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"tmch","sideBox":"Learn more about [Transition Metal Chemistry](http://link.springer.com/journal/11243)","snPcode":"11243","submissionUrl":"https://submission.nature.com/new-submission/11243/3","title":"Transition Metal Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"6e0456c2-13c2-4e3a-a04a-ee6bc815c187","owner":[],"postedDate":"July 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-09-23T16:02:41+00:00","versionOfRecord":{"articleIdentity":"rs-4631763","link":"https://doi.org/10.1007/s11243-024-00609-3","journal":{"identity":"transition-metal-chemistry","isVorOnly":false,"title":"Transition Metal Chemistry"},"publishedOn":"2024-09-16 15:57:36","publishedOnDateReadable":"September 16th, 2024"},"versionCreatedAt":"2024-07-19 19:28:41","video":"","vorDoi":"10.1007/s11243-024-00609-3","vorDoiUrl":"https://doi.org/10.1007/s11243-024-00609-3","workflowStages":[]},"version":"v1","identity":"rs-4631763","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4631763","identity":"rs-4631763","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}