A strategy to improve the performance of MnCe-MOFs/ZSM-5 for formaldehyde degradation at ambient temperature

A strategy to improve the performance of MnCe-MOFs/ZSM-5 for formaldehyde degradation at ambient temperature | 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 A strategy to improve the performance of MnCe-MOFs/ZSM-5 for formaldehyde degradation at ambient temperature Zi-su Yang, Qiong Huang, Xi Tong, Jia-xin Shan, Chen Wei, Jun-jie Mao, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7582325/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Reducing airborne formaldehyde (HCHO) to the indoor environmental standard (0.08 mg/m 3 ) remains challenging when relying solely on physical adsorption. Ambient-temperature catalytic oxidation offers an effective alternative, decomposing HCHO into CO 2 using high performance transition metal oxides. New type metal organic frameworks (MOFs) of monometallic, bimetallic oxides and supported catalysts with different carriers synthesized by the hydrothermal method were investigated in this study. 1.0 g of catalyst powder was dispersed uniformly on the petri dish (Φ=90 mm) and the initial concentration of HCHO was regulated to 1.0±0.5 mg/m 3 . The reaction temperature was set to ambient temperature (25±5°C), and the measurements for HCHO concentration were performed triply every 12 h. Among them, MnCe-MOFs displayed a high degradation rate (96.3%) at 48 h, with notable stability attributed to the synergistic redox cycling of Ce 4+ /Ce 3+ and Mn 3+ /Mn 4+ , which generated abundant reactive oxygen species (ROS, O 2 - and ·OH), along with their excellent hydrophobicity. Electron paramagnetic resonance (EPR) analysis revealed that oxygen-deficient sites facilitate the complete oxidation of HCHO. As for supported catalysts, 20wt%MnCe-MOFs/ZSM-5 also exhibited a high oxidation activity (93.4%) ascribed to abundant active components of MnCe-MOFs, surface week acid sites, high surface areas, and abundant oxygen vacancies, indicating high stability for HCHO oxidation. Metal organic frameworks HCHO Catalysts Catalytic oxidation at ambient temperature Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 1. Introduction Environmental pollution has posed a significant challenge, particularly for developing countries (Yang et al., 2015 ). Among air pollutants, formaldehyde (HCHO) is a colorless, volatile gas with strong irritant properties. It is commonly used in building materials, furniture, glues, cleaners and other indoor products, and is classified as highly toxic substance. This substance is typically emitted in indoor settings, potentially damaging human health (Yusuf et al., 2017 ). Prolonged exposure to HCHO at low levels may lead to various health issues, encompassing problems like breathing difficulties, eye soreness, headaches, vertigo, and coughing. In addition, HCHO has been recognized as a potential carcinogen, and prolonged exposure has been linked to the formation of certain cancers, such as nasopharyngeal cancer (Nie et al., 2016 ). Therefore, indoor HCHO concentration and exposure time are of great importance for human health. Implementing effective strategies to manage air quality and control HCHO emissions is crucial for safeguarding the health and safety of indoor environments (Tunga et al., 2010 ). The treatment techniques for remove indoor HCHO involve a variety of approaches, such as adsorption, photo-catalytic oxidation, catalytic oxidation, and others. For example, a large amount of adsorbents including activated carbon, zeolite and others are applied to adsorb HCHO and purify air (Saleem et al., 2019 ; Kang et al., 2022 ). However, the adsorption method is susceptible to adsorbent saturation, may cause secondary pollution, and is inefficiency at removing low concentration of HCHO. Photocatalytic degradation of HCHO to a harmless substance over various photocatalysts is an effective method, but the catalytic reactions require the use of ultraviolet or visible light (Talaiekhozani et al., 2021 ). Compared to conventional methods, catalytic oxidation processes employing precious metal-based or earth-abundant catalysts under ambient conditions exhibits significantly enhanced efficacy in HCHO degradation. The precious metals (e.g., Pt, Au, Pd, Ag and Rh) are often used as catalysts for efficient oxidation at ambient temperature, but the cost is very high. Researchers have also started to explore the non-noble catalysts, such as MnO 2 , Cr 2 O 3 , Co 3 O 4 , and other, which also exhibit more advantages (Dong et al., 2021; Yang et al., 2021; Huang et al., 2018 ). Manganese oxides have been increasingly employed for HCHO removal due to their high activity, low toxicity, and ready availability (Zhu et al., 2019). To examine the influence of precursor solution pH on the microstructure and surface characteristics of MnO x , a series of experiments were conducted. The results showed that at pH = 13, MnO x exhibited the largest interlayer spacing, alongside the greatest pore diameter and specific surface area. The distinct structural characteristics promoted the generation of numerous manganese vacancies and catalytically active sites, thereby enhancing ROS sequestration and improving catalytic performance in HCHO oxidation (Zhang et al., 2023). Co 3 O 4 was also a potential candidate for VOCs oxidation (Hua et al.,2023; Wu et al.,2024) owing to its unique spinel structure, multivalent state, abundant reactive oxygen, and superior redox performance. Mg-doped Co 3 O 4 was studied, and the resulting catalyst exhibited enhanced catalytic activity for HCHO oxidation at room temperature due to its defect-enriched structure (Meng et al., 2024). Table 1 was a comparison of the effect of catalytic oxidation of HCHO over MnO 2 -based catalysts reported previously. Obviously, the traditional MnO 2 -based catalysts were difficult to disintegrate HCHO at ambient temperature, except for precious metal catalysts with high prices. Table 1 Summarization of literature data on catalytic oxidation of HCHO over MnO x –based catalysts at low temperature Catalyst Preparation condition Test conditions T 50 T 100 References α-MnO 2 Calcined at 140 o C for 12h 170 ppm HCHO, GHSV ~ 100,100 mL/g·h - 140 (Bai et al., 2016 ) β-MnO 2 Calcined at 140 o C for 12h and dried at 120 o C 170 ppm HCHO, GHSV ~ 100,100 mL/g·h - 180 (Bai et al., 2016 ) MnO x -CeO 2 (MP773) Dried at 110 o C for 12h; calcined at 500 ℃for 6 h 580 ppm HCHO, 18% O 2 , He balance, GHSV ~ 30L/g·h > 80 100 (Tang et al., 2006 ) MnO x -CeO 2 (CeMn80) Dried at 110 o C overnight; calcined at 400 o C for 6 h 580 ppm HCHO, 20% O 2 , N 2 balance, GHSV ~ 30L/g·h > 75 100 (Liu et al., 2009 ) Pt/MnO x -CeO 2 Dried at 110 o C for 12h; calcined at 500 o C for 6 h 30 ppm HCHO, 20% O 2 , He balance, GHSV ~ 30L/g·h - RT (Tang et al., 2008 ) Ag/MnO x -CeO 2 Dried at 110 o C for 12h; calcined at 500 o C for 6 h 580 ppm HCHO, 18% O 2 , GHSV ~ 30L/g·h ~ 80 > 90 (Tang et al., 2006 ) Nevertheless, these oxides usually show low catalytic activity under high humidity conditions at ambient temperature, so effective strategies are required to improve their efficiency in HCHO decomposition. Therefore, a variety of new materials have been developed for the removal of indoor HCHO, including gas adsorption, gas storage and catalysis. MOFs have attracted considerable attention due to their unique structural characteristics and exceptional functional properties, such as high specific surface areas, inherent porosity, exceptional chemical stability, and accessible metallic sites. One type of UiO-66 derived MOFs catalysts were generated to degrade HCHO under visible light and exhibited a high activity (Duan et al., 2022 a). MnO 2 /UiO-66-NH 2 MOFs nanocomposite were also prepared to remove gas HCHO. The results showed that MnO 2 /UiO-66-NH 2 can effectively remove HCHO at ambient temperature, but increasing the loading of manganese dioxide diminishes its removal efficiency (Vikrant et al., 2022). The solid solution of Mn x Co 3 -xO 4 prepared using MOFs with varying Co/Mn molar ratios was reported to display superior catalytic efficiency for oxidation under standard ambient conditions. In summary, various MOFs precursors were synthesized and characterized, and their derived oxide catalysts were evaluated for HCHO degradation under ambient conditions. These findings highlight the promising catalytic potential of MOFs-derived materials in HCHO oxidation at low-temperatures (Tu et al., 2021 ). In this study, a series of monometallic and bimetallic MOFs-derived metal oxide catalysts and supported catalysts were synthesized via hydrothermal synthesis and further characterized using X-ray diffraction (XRD), Scanning and transmission electron microscopy (SEM, TEM), H 2 -temperature programmed reduction (H 2 -TPR), NH 3 -temperature programmed desorption (NH 3 -TPD), X-ray spectroscopy (XPS), and electron paramagnetic resonance (EPR). In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was utilized to gain a better understanding of the potential mechanism underlying HCHO degradation over MnCe-MOFs catalysts. This research can provide some new insights into efficient methods to eliminate low indoor concentration of HCHO at ambient temperature. 2. Materials and Methods 2.1. Catalyst preparation The synthesis of MnCe-MOFs catalysts via a hydrothermal process incorporating N, N-dimethylformamide (DMF) was conducted in a series of steps to enable the catalytic degradation of HCHO. First, 4.2g of 1, 3, 5-benzoic acid (H 3 -BTC) were added to 50 mL of DMF solution and stirred until completely dissolved to obtain solution A. Second, 1.45g of Ce(NO 3 ) 3 ·6H 2 O and 3.87mL of 50% Mn(NO 3 ) 2 solution were added to 10 mL distilled water and stirred until completely dissolved to obtain solution B. Subsequently, solution B was gradually introduced into solution A under continuous stirring for 15 minutes, followed by transferring the resultant mixture into a Teflon-lined autoclave and maintaining it at 120°C for an 8-hour hydrothermal treatment. After that, the powered products were obtained by centrifugation and washed separately three times with H 3 -BTC and ethanol. The final processing steps involved drying the samples for 5 hours at 80°C, followed by calcination for 3 hours at 500°C. The catalysts synthesized with a Mn:Ce molar ratio of 5:1 were designated as MnCe-MOFs. The studied catalysts, including monometallic MOFs catalysts and supported catalysts (MnCe-MOFs/ZSM-5, MnCe-MOFs/Al 2 O 3 , and MnCe-MOFs/palygorskite) with various loading amount were all synthesized using the same procedure. 2.2. Characterization The crystallographic features of the catalysts were characterized via X-ray diffraction (XRD) analysis (XRD-6100, Bruker, Germany) employing a CuKα radiation-based diffractometer. The measurements were conducted over an angular range of 10°–80° at a rate of 8° per minute. Morphological examination and high-resolution imaging of the microstructure and crystalline phases were performed using the scanning electron microscope (SEM, Hitachi, Japan) and the transmission electron microscope (TEM, FEI, USA) techniques. Energy dispersive spectroscopy (EDS) was utilized to analyze the elemental composition and map the spatial distribution of active sites, thereby providing insights into their microstructural features. The specific surface area, pore volume, and pore size distribution were analyzed using the BET and BJH model, with data acquired via an ASAP 2460 analyzer (Hitachi, Japan). The redox behavior of the catalyst was investigated via hydrogen temperature-programmed reduction (H 2 -TPR) analysis, enabling the evaluation of its reduction kinetics and active site distribution. The catalyst samples (50 mg) were exposed to an argon gas flow for pretreatment purposes at 300 o C for 30 min. After that, a 10% H 2 /Ar mixture flow (30 mL/min) was introduced, and the reactor was heated at a rate of 10 o C·min − 1 from environmental temperature to 800 o C. The temperature programmed desorption of O 2 (O 2 -TPD) was carried out on the same apparatus as for H 2 -TPR to investigate the location of active oxygen in the catalyst. The measurement was performed over a temperature range of 60–800℃, with a heating rate of 15 ℃/min. NH 3 temperature programmed desorption (NH 3 -TPD) detected by the TCD was applied to characterize the surface acidity and distribution of acid strengths on the catalyst. Surface-related elemental composition, chemical bonding states, and electronic configurations were characterized using X-ray photoelectron spectroscopy (XPS, Thermo ESCALAB 250XI, USA). An Al Kα radiation source was used with the energy of 1486.8 eV, the tube voltage of 15 kV, and the current of 10 mA, respectively. Additionally, surface unpaired electrons were characterized via electron paramagnetic resonance (EPR) to evaluate the influence of oxygen vacancies on the catalytic material's performance. 2.3. Performance evaluation Under conditions simulating an indoor quiet environment, the catalytic oxidation efficacy of the catalysts was assessed using a 0.125 m 3 sealed glass container. First, 1.0 g of MnCe-MOFs powder catalyst was uniformly dispersed across a 90 mm diameter petri dish and positioned at the reactor's base. The starting concentration of HCHO was regulated to 1.0 ± 0.5 mg/m 3 by volatilization of HCHO solution and measured by HCHO analyzer (PPM-400st, UK). After that, the reactor was enclosed with a large amount of vaseline to prevent a decrease in HCHO concentration without catalysts. Environmental temperature stabilized at 25 ± 5°C, with concentration measurements performed triply every 12 hours. The catalytic oxidation performance of the catalysts was calculated by determining the HCHO degradation rate via Eq. (1): η (%) = 1-[( C 0 - C t )]/ C 0 ×100% (1) where C 0 denotes the initial HCHO concentration; C t represents the concentration of gaseous HCHO at time; η denotes the degradation rate. 3. Results and discussion 3.1. Characterization analysis 3.1.1. XRD The crystal structures of Mn-MOFs and MnCe-MOFs calcined at 500 o C were investigated by XRD. As shown in Fig. 1 (a), the diffraction peaks at 2θ = 18.0°, 28.9°, 32.3°, 36.1°, 38.0°, and 64.7° correspond to the (101), (112), (103), (211), (004) and (400) crystal planes of Mn 3 O 4 (PDF#24–0734), which are attributed to MnO and Mn 2 O 3 , respectively. The peaks at 2θ = 28.5°, 33.1°, 47.5°, 56.3°, 59.1°, 69.4°, 76.7°, and 79.1° correspond to the (111), (200), (220) and (311), (222), (400), (331) and (420) of CeO 2 (PDF#43-1002). Previous studies have demonstrated that the ionic radius of Mn 3+ (0.066 nm) is smaller than that of Ce 4+ (0.094 nm), and the characteristic diffraction peak of Mn 3 O 4 in MnCe-MOFs exhibits a weaker intensity compared to Mn-MOFs. This is attributed to the inhibitory effect of CeO 2 on Mn 3 O 4 crystal growth (Kan et al., 2017 ; Wang et al., 2017 ), thereby facilitating the incorporation of Mn into the CeO 2 lattice to form a solid solution (Niu et al., 2020 ; Sihaib et al., 2017 ). The XRD patterns of MnCe-MOFs with different loading amounts supported on ZSM-5 were shown in Fig. 1 (b). The results showed that these MnCe-MOFs/ZSM-5 catalysts were similar, and the intensities of the diffraction peaks of ZSM-5 (PDF#42–0120), observed at 2θ = 13.2°, 13.9°, 14.7°, 23.0°, 23.8°, 29.8°, 44.9°and 45.4°, gradually decreased as MnCe-MOFs loading increased, due to enhanced surface coverage of active components on ZSM-5. As the MnCe-MOFs supporting amount enhanced, the characteristic diffraction peaks at 2θ = 28.5°, 47.4°, and 36.1° could be detected in this sample, indicating the creation of a solid solution phase comprising manganese and cerium oxide constituents. The above result also demonstrated that the crystal size increased with the enhancing supporting amount, which was also beneficial for the improvement of HCHO degradation, but the oxidation rate decreased. Compared to conventional MnOx-CeO 2 composites requiring complex synthesis or high Mn:Ce ratios (Miao et al., 2019 ), our MnCe-MOFs achieved atomic-level mixing of Mn and Ce via a single-step hydrothermal method (Mn:Ce = 5:1). This structural homogeneity, evidenced by EPR and H 2 -TPR, facilitated abundant oxygen vacancies and enhanced oxygen mobility. MOFs-derived materials retain the highly ordered porous structures and ultrahigh surface areas from their MOFs precursors, facilitating efficient mass transfer and abundant exposure of active site. For example, MnCe-MOFs demonstrated a specific surface area of 370.48 m²/g (Table 1 ), far exceeding typical metal oxides like MnO 2 (Zhang et al., 2022 ). This structural advantage facilitates enhanced adsorption and catalytic degradation of HCHO at ambient temperature. 3.1.2. BET To examine the influence of support material and loading quantity on catalysts' specific surface area and pore dimensions, BET measurements were conducted on representative samples (Table 2 and Fig. 2 ). The specific surface area and pore dimensions of MnCe-MOFs/ZSM-5 catalysts decreased with increasing MnCe-MOFs loading, possibly due to the successful dispersion of MnCe-MOFs active components on the high-surface-area and low-pore-size ZSM-5 support. The findings further revealed that catalytic performance was influenced by parameters beyond surface area characteristics, with the MnCe-MOFs active component serving as a critical contributor to its functionality. However, compared to ZSM-5, the MnCe-MOFs supported on Al 2 O 3 and palygorskite exhibited lower surface area and larger pore size, which was not conducive to improved performance, as the support materials failed to provide sufficient active site for enhanced adsorption and oxidation. The BET results indicated that ZSM-5 was superior to Al 2 O 3 and palygorskite as a support due to its porous structure, which facilitates the diffusion of HCHO molecules and enhance contact between HCHO and the active sites, thereby facilitating HCHO oxidation at ambient temperature. Table 2 Specific surface area, pore volume and size of these catalysts Samples Specific surface area (m 2 /g) Pore volume (cm 3 /g) Average aperture (nm) MnCe-MOFs/ZSM-5 (2%) 370.5 10.1 5.5 MnCe-MOFs/ZSM-5 (40%) 263.5 10.2 9.5 MnCe-MOFs/Al 2 O 3 (40%) 29.2 10.1 12.7 MnCe-MOFs/palygorskite (40%) 53.7 10.2 10.8 As shown in Fig. 2 (a), the MnCe-MOFs-500/ZSM-5 catalyst exhibits a Type IV-type isotherm (Thommes et al., 2015 ) and shows a significant increase in adsorption due to capillary condensation in the moderate relative pressure region ( p / p 0 ~ 0.4 − 0.8). The desorption branch presents a H4-type hysteresis loop at p / p 0 ~ 0.4 − 0.5 (Fig. 2 (a)). According to IUPAC classification, the Type IV-type isotherm indicates a mesoporous structure (2–50 nm), while the H4-type hysteresis loop suggests the microporous-mesoporous composite pore characteristics, such as the synergistic interaction between micropores in the ZSM-5 support and mesopores in the MnCe-MOFs active components. This interpretation aligns with the pore size distribution results (Fig. 2 (b)). The MnCe-MOFs catalysts loaded on Al 2 O 3 and palygorskite also exhibit Type IV-type isotherms, but accompanied by H3-type hysteresis loops (Fig. 2 (a)). According to IUPAC definitions, H3 hysteresis loops are typically associated with non-rigid layered particle aggregation structures or open mesopores. In conjunction with its BET data (Table 2 ), the low specific surface area (29.21 m 2 /g) and large average pore size (12.7 nm) of MnCe-MOFs/Al 2 O 3 indicate that the active components primarily cover the surface of the support, forming a loosely packed mesoporous structure. The broad pore size distribution (10.8 nm) of MnCe-MOFs/palygorskite, however, aligns with the interlayer pore characteristics of natural fibrous clay supports. Additionally, commercially available ZSM-5, due to its well-defined microporous framework (pore size < 2 nm) and high specific surface area (370.5 m 2 /g), can provide abundant anchoring sites for MnCe-MOFs, promoting uniform dispersion of active components and forming micro-porous-mesoporous composite channels, thereby optimizing the diffusion and oxidation performance of HCHO molecules. 3.1.3. SEM and TEM The relationship between compositional variations and the microstructural properties of the catalysts, including their morphological features, was systematically analyzed. Figure 3 exhibited the SEM and TEM images of Mn-MOFs (a, b, c, d) and MnCe-MOFs (e, f, g, h). Mn-MOFs calcined at 500 o C displayed a large interlayer void, a disrupted skeleton, and a relatively rough surface morphology, with numerous spherical Mn 3 O 4 nanoparticles, which facilitated the catalytic reaction. However, compared to Mn-MOFs, MnCe-MOFs exhibited an abundant surface structure with more uniformly loose spherical nanoparticles composed of CeO 2 and Mn 3 O 4 , which was beneficial for improving performance. Meanwhile, crystal structures of Mn 3 O 4 and CeO 2 , exhibiting lattice fringes of 0.25 nm and 0.31 nm, corresponding to (2 1 1) and (1 1 1) planes, were observed on the main exposed surface of Mn-MOFs and MnCe-MOFs, respectively, in agreement with the XRD results. Moreover, some amorphous metal oxides can be observed in the MnCe-MOFs, which is attributed to the ability of cerium oxide to inhibit the growth of manganese oxide crystals, and to the synergistic effects of bimetallic Mn-Ce oxiders; both factors contribute to improving oxidative activity. To evaluate the spatial dispersion of elements in Mn-MOFs catalysts and MnCe-MOFs catalysts, the Mn, Ce and O elemental mapping was performed in Fig. 4 . The analysis showed an even distribution of Mn and O components on the Mn-MOFs surface, suggesting their integration into the Mn 3 O 4 lattice structure. Meanwhile, the Mn, Ce and O also dispersed homogeneously on the surface of MnCe-MOFs. Furthermore, the low content of Ce was highly dispersed owing to the uniform self-assembly arrangement, providing the potential synergism with manganese oxide to enhance electron transfer efficiency and improve active site availability, thereby boosting HCHO oxidation performance. 3.1.4. H 2 -TPR The reducibility of the Mn-MOFs, Ce-MOFs, and MnCe-MOFs catalysts was determined by H 2 -TPR (Fig. 5 ). The peak observed at 250°C in Mn-MOFs was attributed to the reduction of MnO 2 /Mn 2 O 3 to Mn 3 O 4 , while the peak at 359°C corresponded to the reduction of Mn 3 O 4 to MnO (Hu et al., 2021 ). The Mn-MOFs sample exhibited remarkable low-temperature reduction capability, attributed to the coexisting valence states of manganese and the dynamic behavior of oxygen species, which collectively contributed to its enhanced catalytic performance toward HCHO oxidation under ambient conditions. However, no reduction peak was observed in the Ce-MOFs due to their low redox performance at low temperatures. While Ce was introduced into Mn-MOFs and derived the bimetal mixed oxide, the reduction peak shifted to lower temperatures, indicating an increase in oxygen fluidity (Azalim et al., 2011 ; Quiroz et al., 2015 ). Therefore, MnCe-MOFs exhibited significantly enhanced redox performance, and the two reduction temperatures were reduced by 11 o C, attributed to the synergism of Mn and Ce, which reduced the bonding energy between cations and oxygen ions while enhancing oxygen mobility (Venkataswamy et al., 2015 ). The lower temperature of H 2 reduction for MnCe-MOFs implied the higher oxygen mobility participated in the oxidation reaction, which was conducive to the removal of HCHO at ambient temperature. 3.1.5. O 2 -TPD analysis Research has shown that in transition metal oxides, oxygen typically desorbs in three distinct temperature zones: molecular adsorbed oxygen (O 2 ) at 50 to 350℃, atomic adsorbed oxygen (O-) at 350 to 750℃, and lattice oxygen (O 2− ) at temperatures above 750℃. Among these, adsorbed oxygen is more prone to desorption compared to lattice oxygen (Bai et al., 2013 ; Bai et al., 2014). As shown in Fig. 6 , the MnCe-MOFs/ZSM-5 catalyst shows two smaller peaks at 95°C and 125°C, which likely correspond to the desorption of physically adsorbed O 2 molecules. Peaks at 336°C, 546°C, and 676°C might correspond to the desorption of chemically adsorbed atomic oxygen (O − ). These peaks suggest that the MnCe-MOFs/ZSM-5 catalyst surface contains a significant amount of active oxygen species, which desorb at lower temperatures, indicating their potential role in catalytic reactions. Compared to Mn-MOFs and MnCe-MOFs catalysts, MnCe-MOFs/ZSM-5 exhibits oxygen species desorption peaks at lower temperatures (e.g., 95°C and 125°C), suggesting a higher concentration of active oxygen species on its surface, which may facilitate the oxidation of HCHO. Although MnCe-MOFs also shows a low desorption temperature, it may not have as rich or active oxygen species as MnCe-MOFs/ZSM-5. The higher desorption temperature of Mn-MOFs may result in lower participation of active oxygen species at room temperature, thereby affecting its catalytic performance. 3.1.6. NH 3 -TPD analysis Studies have demonstrated that the catalyst's acidic properties are critical to affect the oxidation process of VOCs, and that the C-H bond is broken at these acidic sites. First, weak acid sites enhance the adsorption of HCHO molecules on the catalyst surface through hydrogen bonding or electrostatic interactions, bringing them closer to active redox sites, such as Mn 3+ /Mn 4+ and Ce 3+ /Ce 4+ . This reduces the activation energy of C-H bonds and accelerates subsequent oxidation reactions (Huang et al., 2020 ). Second, the acidity of weak acid sites is moderate, allowing for effective promotion of C-H bond cleavage in HCHO through proton H + transfer, generating intermediate products (Quiroz et al., 2015 ). This also avoids the excessive adsorption or accumulation of intermediates caused by strong acid sites. Additionally, the interaction between weak acid sites and surface hydroxyl groups (-OH) or reactive oxygen species (e.g., \(\:{O}_{2}^{-}\) and •OH) enhances the stability of these reactive oxygen species (Zhang et al., 2021 ), enabling their continuous participation in the deep oxidation of HCHO, ultimately converting it into CO 2 and H 2 O. To explore the relationship between the surface acidity of MnCe-MOFs loaded on different supporters and their activity, NH 3 -TPD analysis were conducted (Fig. 7 ). Three types of catalysts showed desorption peaks at 122 o C, 114 o C and 95 o C in the weak acid region, respectively. The result indicated that MnCe-MOFs/ZSM-5 displayed the highest weak acidity and lowest desorption peak temperature, which was beneficial for improving oxidation performance. Meanwhile, the medium and strong acidity levels of MnCe-MOFs/ZSM-5 and MnCe-MOFs/Al 2 O 3 were relatively low, whereas MnCe-MOFs/palygorskite exhibited increased acidity, especially in the strong acid region, which was detrimental to the optimal performance. The above results demonstrated that the MnCe-MOFs loaded on different supporters exhibited varying acidity, which in turn led to differences in oxidation properties, mainly due to the presence of weak acid sites. Leveraging the high specific surface area and ordered pore structure of the ZSM-5 support, the presence of weak acid sites further improves the contact efficiency between HCHO molecules and active components, thereby synergistically enhancing the catalyst’s oxidation activity and cycling performance. Ultimately, this results in excellent catalytic effects of MnCe-MOFs/ZSM-5 in the degradation of HCHO at low concentrations and room temperature. Supported MnO 2 catalysts show limited stability due to weak metal-support interactions (Miao et al., 2019 ). ZSM-5 high surface area (370 m 2 /g) and weak acid sites promote HCHO adsorption and intermediate oxidation, while the MOFs-derived active components prevent aggregation, ensuring long-term stability. 3.1.7. XPS To further quantify the chemical state of the surface elements of Mn-MOFs catalysts and MnCe-MOFs catalysts, the binding energies of Mn 2p, Ce 3d and O 1s were analyzed by XPS (Fig. 8 ). The Mn 2p spectrum divided into Mn 2p 3/2 and Mn 2p 1/2 with the binding energies at 641.7 eV and 653.3 eV, respectively. The Mn 2p 3/2 XPS peaks were decomposed into three distinct peaks at binding energies of 640.2 eV, 641.8 eV, and 644.2 eV, corresponding to Mn 2+ , Mn 3+ and Mn 4+ , respectively. This confirmed the presence of mixed valence states in Mn, with a Mn 3+ /Mn 4+ ratio of 1.06 calculated based on peak area integration. The coexistence of manganese in diverse valence states can enhance the generation of abundant oxygen vacancy sites and surface undercoordinated bonds, thereby accelerating the oxidation reaction kinetics (Yang et al., 2018 ). While the characteristic peak areas of Mn decreased, the Mn 3+ /Mn 4+ ratio also dropped from 1.06 to 0.99, suggesting an elevated Mn 4+ concentration in MnCe-MOFs as a result of Ce incorporation. Figure 8 (b) showed the Ce 3d XPS spectra of MnCe-MOFs, which can be divided into peaks at 882.4 eV, 888.7 eV, 898.3 eV, 900.9 eV, 907.3 eV, and 916.7 eV corresponding to Ce 4+ , and at 884.6 eV and 903.2 eV assigned to Ce 3+ . The presence of Ce 3+ also induced the charge imbalance, generating unsaturated chemical bonds and oxygen vacancies, and these lattice oxygen storage and transfer between Ce 3+ and Ce 4+ was conducive to the oxidation reaction (Zhang et al., 2020 ). Figure 8 (c) shows the O 1s XPS spectra of Mn-MOFs and MnCe-MOFs, which can be deconvoluted into two peaks at binding energies of 531.3 eV and 529.7 eV, corresponding to surface oxygen species ( O sur ) and lattice oxygen ( O latt ), respectively. The conversion pathways of oxygen were usually O 2 (sur)→ O 2− (sur) → O − (sur) → O 2− (lat). O sur was found to participate in oxidation reactions, and higher concentrations of O sur enhanced oxidation activity, while a high concentration of O lat facilitated C-H bond cleavage (Liu et al., 2012 ). The results exhibited that O sur could quickly transfer and replenish the consumed O lat to maintain the oxygen balance. 3.1.8. EPR To detect the oxygen vacancies of the sample, an EPR test was performed (Fig. 9 ). A g = 2.003 signal was detected in all samples, because of oxygen vacancies in the material (Zhao et al., 2021 ; Zhou et al., 2023 ). Oxygen vacancy signals exhibited a descending intensity sequence: MnCe-MOFs/ZSM-5 > MnCe-MOFs/Al 2 O 3 > MnCe-MOFs > Mn-MOFs, which indicates that the interaction between MnCe-MOFs and ZSM-5 carriers result in more oxygen vacancies, while MOFs materials without loading form fewer oxygen vacancies than their loaded counterparts. Oxygen vacancy as an electron enrichment facilitates O 2 adsorption, activation and formation of superoxide radical (• \(\:{O}_{2}^{-}\) ) or lattice oxygen (O − ), which directly participates in the deep oxidation of HCHO (HCHO→CO 2 + H 2 O) (Huang et al., 2020 ). Hence, MnCe-MOFs/ZSM-5 demonstrates superior catalytic performance. While composite catalysts (MnOx-CeO 2 ) enhance activity through Mn 3+ /Mn 4+ and Ce 3+ /Ce 4+ redox cycles, such composites typically require high Mn:Ce ratios or complex synthesis methods (Miao et al., 2019 ). Our MnCe-MOFs derive from a single-step hydrothermal process with a Mn:Ce ratio of 5:1. As shown in EPR patterns, the MOFs structure ensures atomic-level mixing of Mn and Ce, creating abundant oxygen vacancies and facilitating O 2 activation. Meanwhile, H 2 -TPR confirms a 50℃ reduction in peak temperature for MnCe-MOFs compared to Mn-MOFs, indicating enhanced oxygen mobility. 3.2. Catalyst performance evaluation The oxidation activities of these monometallic oxides, bimetallic oxides, and supported catalysts were all evaluated by a low concentration of HCHO under ambient temperature. The activities of these MOFs catalysts, composed of six different types of monometallic oxides, were evaluated for HCHO degradation (Fig. 10 ). These catalysts displayed significant differences in oxidation according to the different property of these monometallic oxides. Among them, Mn-MOFs catalysts exhibited the highest activities for HCHO oxidation. HCHO concentration was reduced from 1.062 mg/m 3 to 0.008 mg/m 3 within 48 h, and a 99.3% degradation rate was achieved due to the unique structure of MOFs, their lower H 2 reduction peak temperature, and the presence of multiple manganese valence states. Although Cu-MOFs exhibited a larger H 2 reduction peak area at 269 o C, it showed the lowest removal rate of 14.0% in these samples. The order of HCHO degradation among these samples was observed as follows: Cu-MOFs < Co-MOFs < Fe-MOFs ≈ Ce-MOFs < Cr-MOFs < Mn-MOFs. Although Mn-MOFs had the optimum oxidation performance, the degradation rate decreased from 99.3% to 82.6% after five cycles of experiments with a poor stability, which may be attributed to the poor ability of water vapor resistance. Therefore, the performances of MOFs-derived bimetallic oxides (MnFe-MOFs, MnCu-MOFs, MnCo-MOFs, MnCr-MOFs, and MnCe-MOFs) for HCHO degradation were investigated and are presented in Fig. 11 to evaluate their effectiveness in enhancing stability. The result exhibited that the oxidation activities of these MOFs-derived bimetallic oxides were all lower than Mn-MOFs. Among them, the MnCe-MOFs and MnCu-MOFs showed the highest (96.3%) and lowest (81.7%) degradation efficiency, respectively. Then, five cycles of experiments demonstrated that the degradation rate of HCHO consistently remained above 96% using MnCu-MOFs catalysts. Mn-MOFs degraded to 82.6% due to poor water resistance (Huang et al., 2020 ). This stability is attributed to hydrophobic MOFs frameworks and robust metal-oxide interactions. Meanwhile, the level of HCHO was below the regulatory limit (0.08 mg/m 3 ) at 48 h, indicating that the cerium oxide doping could improve the stability of the MOFs-derived monometallic oxides. To evaluate the influence of support materials on the catalytic oxidation performance of MnCe-MOFs-based catalysts, ZSM-5, Al 2 O 3 , and palygorskite powder were selected to support MnCe-MOFs active components (Fig. 12 ). The performances of these catalysts, each containing 40% MnCe-MOFs support, show only subtle difference, yet all exhibited excellent performance owing to the active components of MnCe-MOFs. Among the catalysts tested, MnCe-MOFs/ZSM-5 demonstrated the highest catalytic activity, attributed to ZSM-5's high surface area and abundant weak acid sites. The HCHO concentration was reduced from 1.038 mg/m 3 to 0.04 mg/m 3 within 48 h, and the degradation rate reached 96.2% using MnCe-MOFs/ZSM-5 at ambient temperature. To further enhance performance and reduce costs, the study examined the effect of the loading amount of MnCe-MOFs/ZSM-5 on oxidation activities (Fig. 13 (a)). The activities significantly decreased with the reduction in the amount of supported MnCe-MOFs active components. The HCHO removal rate declined from 96.2% to 57.6% as the MnCe-MOFs loading decreased from 40% to 2%. MOFs allow precise control over metal ratios and organic linkers, enabling customized active sites. By optimizing the ZSM-5 loading, MnCe-MOFs/ZSM-5 achieved 93.4% degradation rate of HCHO, a performance that is difficult to attain with conventional oxides (Huang et al., 2020 ). According to the above results, the stability experiments of MnCe-MOFs/ZSM (20%) were conducted (Fig. 13 (b)). The activity remains nearly constant in the five consecutive cycles of experiments, and the degradation rates of HCHO were 93.4%, 92.7%, 92.8%, 93.2% and 93.1% at 48 h, respectively. Therefore, it demonstrated that the MnCe-MOFs/ZSM-5 (20%) was a kind of excellent catalysts for HCHO degradation at ambient temperature in indoor environment. 3.3. Reaction mechanism To elucidate the HCHO oxidation mechanism, operando infrared spectroscopy was employed to analyze the redox behavior of MnCe-MOFs under HCHO/N 2 and HCHO/O 2 atmospheres at ambient temperature (Fig. S1 ). The findings revealed comparable vibrational peak positions between HCHO/N 2 and HCHO/O 2 environments, though spectral intensities exhibited distinct variations. The peaks at 3710 cm − 1 and 1660 cm − 1 were assigned to the bending vibration of H 2 O and the hydroxyl group that is adsorbed on the surface. The peak at 3660 cm − 1 corresponded to the stretching vibration model ν (OH) of the structural hydroxyl group, and its intensity gradually decreased over time in HCHO/N 2 , while remaining stable in HCHO/O 2 , indicating that hydroxyl (OH) groups were consumed during HCHO oxidation in HCHO/N 2 and replenished in HCHO/O 2 . The broad absorption band observed at 3480 cm − 1 corresponds to an overlapping signal originating from hydrogen-bonding interactions, as well as the in-phase and out-of-phase stretching vibrations of H 2 O molecules. This indicates water generation during HCHO oxidation, which subsequently facilitates HCHO adsorption and dissociation on the catalyst surface. The absorption peak at 3240 cm − 1 corresponds to the C-H stretching vibration ν (CH) of format, while the peaks at 2840 cm − 1 and 1060 cm − 1 are assigned to the CH stretching vibration ν (CH) and CO stretching vibration ν (CO), respectively, originating from dioxymethylene (DOM), which is the primary intermediate in the HCHO oxidation process. The data revealed a progressive attenuation of DOM intensity under HCHO/N 2 conditions, whereas its enhancement was observed in HCHO/O 2 environment. This implies that the presence of oxygen leads to the generation of reactive oxygen species (ROS) on the catalyst surface, thereby facilitating the oxidative decomposition of HCHO. Concurrently, the peak at 2340 cm − 1 corresponds to CO 2 adsorption, indicating that CO 2 is the terminal oxidation product of HCHO. The peaks at 1560cm − 1 , 1460 cm − 1 , and 1360 cm − 1 corresponded to COO asymmetric stretching vibration ν (COO), CH bending vibration δ (CH), and COO symmetric stretching vibration ν s (COO), respectively. Based on the above activity and characterization analysis results, the proposed mechanism of MnCe-MOF catalysts for formaldehyde oxidation is depicted in Fig. 14 . HCHO is adsorbed onto the catalyst surface through hydrogen bonding interactions, while O₂ undergoes dissociation to reactive oxygen species and surface hydroxyl group during the initial reaction stages. Then, these HCHO molecules participated in the redox reaction with these MnO x and CeO 2 active components under active oxygen species and surface hydroxyl group. Meanwhile, the intermediate products of dioxymethylene (DOM), formate and else produced and then further oxidized to carbonic acid under the action of lattice oxygen, which was unstable and quickly decompose into CO 2 and H 2 O. Simultaneously, there was a mutual promotion between Mn 3 O 4 and CeO 2 , which could achieve oxygen transfer through the change of Mn 3+ /Mn 4+ and Ce 4+ /Ce 3+ valence states, leading to abundant oxygen vacancy sites and diverse oxygen species, which facilitated the catalytic oxidation of formaldehyde over MnCe-MOF catalysts. 4. Conclusion In this study, a series of novel metal-organic frameworks (MOFs)-based catalysts, including monometallic, bimetallic oxide, and supported catalysts with varied carriers, were synthesized via the hydrothermal method and evaluated for their catalytic oxidation performance toward HCHO degradation at ambient temperature. The results exhibited that the Mn-MOFs, MnCe-MOFs, and MnCe-MOFs/ZSM-5 displayed over 95% HCHO degradation rates at 48h, attributed to reactive oxygen species (ROS, O 2 − and ·OH) instead of physical adsorption. Meanwhile, compared to the Mn-MOFs, their stability and reaction mechanism were analyzed. The results demonstrated that MnCe-MOFs exhibited significantly higher stability due to their excellent resistance to water vapor and the cooperation of Mn 3+ /Mn 4+ and Ce 4+ /Ce 3+ valence states. As for supported catalysts, MnCe-MOFs/ZSM-5 prepared with 20 wt% supporting amount displayed a high oxidation activity (93.4%) and optimal cost-effectiveness, attributed to the synergistic effects of MnCe-MOFs active components and the favorable surface properties (including weak acidity, high surface area, abundant oxygen vacancies) provided by the ZSM-5 support, demonstrating good stability for HCHO oxidation. Abbreviations formaldehyde HCHO H 2 -temperature programmed reduction H 2 -TPR metal organic frameworks MOFs NH 3 -temperature programmed desorption NH 3 -TPD Electron paramagnetic resonance EPR X-ray spectroscopy XPS X-ray diffraction XRD In situ diffuse reflectance infrared Fourier transform spectroscopy DRIFTS Scanning electron microscopy SEM N, N-dimethylformamide DMF transmission electron microscopy TEM dioxymethylene DOM 1, 3, 5-benzoic acid H 3 -BTC Declarations Ethics and consent to participate This manuscript does not involve human tissue or related experiments. Competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work; there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled. Author contribution All authors contributed to the work. Zisu Yang, Qiong Huang, Tao Tao and Mindong Chen were involved in conceptualization. Zisu Yang, Xi Tong, Jia-xin Shan, Qiong Huang and Mindong Chen contributed to methodology. Zisu Yang, Xi Tong, Jia-xin Shan, Jun-jie Mao, Chen Wei, Dawei Li and Bo Yang involved in formal analysis. Zisu Yang, Xi Tong, Jia-xin Shan and Dawei Li involved in data curation. Zisu Yang and Qiong Huang wrote the original draft. Tao Tao, Hong Yang and Bing Li completed language modification. Funding This research was supported by Natural Science Foundation of Jiangsu Province (No. BK20201389, BK20190786, and BK20170954), the National Natural Science Foundation of China (No. 21501097 and 51902166), the Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYCX23-1384), the Qing Lan Project of the Jiangsu Higher Education Institutions, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and NUIST-Reading Research Institute Pump-Priming Project. Availability of data and materials The authors confirm that the data supporting the findings of this study are available within the article or as its supplementary materials. Acknowledgments All individuals who have contributed to this article have been included in the co-authors. References S. Azalim, M. Franco, R. Brahmi, et al. Removal of oxygenated volatile organic compounds by catalytic oxidation over Zr–Ce–Mn catalysts. 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catalysts\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/25940b3314807bbcb5dc8dd0.png"},{"id":92013498,"identity":"207c69f6-a9a4-4bdb-a938-e4eb11411b06","added_by":"auto","created_at":"2025-09-23 16:05:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":51772,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of Mn 2p (a), Ce 3d (b), and O 1s (c)\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/fd8bfca15402a2e0f1538ae4.png"},{"id":92010884,"identity":"7be3fbe7-0724-450b-b94c-b2a969d3ace9","added_by":"auto","created_at":"2025-09-23 15:41:25","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":33208,"visible":true,"origin":"","legend":"\u003cp\u003eEPR patterns of Mn-MOFs, MnCe-MOFs, MnCe-MOFs/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and MnCe-MOFs/ZSM-5 catalysts\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/8c46c9315926eccccbe2bf62.png"},{"id":92010879,"identity":"397a6faf-8cd9-4eaa-b110-860018b752c8","added_by":"auto","created_at":"2025-09-23 15:41:25","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":54726,"visible":true,"origin":"","legend":"\u003cp\u003ePerformance of MOFs-derived monometallic oxides for HCHO oxidation\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/3ac1a329b6ead4f05d8fd437.png"},{"id":92012899,"identity":"a782de39-e72d-43c6-a19b-1fadcfa6da5a","added_by":"auto","created_at":"2025-09-23 15:57:25","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":26938,"visible":true,"origin":"","legend":"\u003cp\u003ePerformance of MOFs-derived bimetallic oxides for HCHO oxidation\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/11ddc17e5d16cfee0648a3f8.png"},{"id":92010876,"identity":"9ab624fc-f4f4-4777-bbd3-ffa57b707249","added_by":"auto","created_at":"2025-09-23 15:41:25","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":27873,"visible":true,"origin":"","legend":"\u003cp\u003ePerformance of MnCe-MOFs supported catalysts for HCHO oxidation\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/4612f49f0249328dfdeab368.png"},{"id":92011785,"identity":"e78fb67f-f379-44c2-ac2b-b74a8fc5a7e9","added_by":"auto","created_at":"2025-09-23 15:49:25","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":58867,"visible":true,"origin":"","legend":"\u003cp\u003ePerformance of MnCe-MOFs/ZSM-5 for HCHO oxidation under different MnCe-MOFs supporting amounts (a) and stability experiments of MnCe-MOFs/ZSM-5 (20%) (b)\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/7cf7b2ec348f93b19b8f0055.png"},{"id":92010890,"identity":"11689d5d-e31f-4767-b458-a9c634b97ba7","added_by":"auto","created_at":"2025-09-23 15:41:25","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":183324,"visible":true,"origin":"","legend":"\u003cp\u003ePossible mechanism of catalytic oxidation of HCHO over MnCe-MOFs catalyst\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/1ce90530accfc012752f4269.png"},{"id":93353600,"identity":"15773424-f722-466a-b564-3b05fa739797","added_by":"auto","created_at":"2025-10-12 22:01:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2172097,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/919afe72-28ed-486c-b77d-1c061b0df82f.pdf"},{"id":92011776,"identity":"f23fa699-94fd-4375-9009-d3e81a8aeaa8","added_by":"auto","created_at":"2025-09-23 15:49:24","extension":"doc","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":235008,"visible":true,"origin":"","legend":"","description":"","filename":"Supportinginformation.doc","url":"https://assets-eu.researchsquare.com/files/rs-7582325/v1/cd0995cb8a52bcf04d25cb52.doc"}],"financialInterests":"No competing interests reported.","formattedTitle":"A strategy to improve the performance of MnCe-MOFs/ZSM-5 for formaldehyde degradation at ambient temperature","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eEnvironmental pollution has posed a significant challenge, particularly for developing countries (Yang et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Among air pollutants, formaldehyde (HCHO) is a colorless, volatile gas with strong irritant properties. It is commonly used in building materials, furniture, glues, cleaners and other indoor products, and is classified as highly toxic substance. This substance is typically emitted in indoor settings, potentially damaging human health (Yusuf et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Prolonged exposure to HCHO at low levels may lead to various health issues, encompassing problems like breathing difficulties, eye soreness, headaches, vertigo, and coughing. In addition, HCHO has been recognized as a potential carcinogen, and prolonged exposure has been linked to the formation of certain cancers, such as nasopharyngeal cancer (Nie et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Therefore, indoor HCHO concentration and exposure time are of great importance for human health. Implementing effective strategies to manage air quality and control HCHO emissions is crucial for safeguarding the health and safety of indoor environments (Tunga et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe treatment techniques for remove indoor HCHO involve a variety of approaches, such as adsorption, photo-catalytic oxidation, catalytic oxidation, and others. For example, a large amount of adsorbents including activated carbon, zeolite and others are applied to adsorb HCHO and purify air (Saleem et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Kang et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, the adsorption method is susceptible to adsorbent saturation, may cause secondary pollution, and is inefficiency at removing low concentration of HCHO. Photocatalytic degradation of HCHO to a harmless substance over various photocatalysts is an effective method, but the catalytic reactions require the use of ultraviolet or visible light (Talaiekhozani et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Compared to conventional methods, catalytic oxidation processes employing precious metal-based or earth-abundant catalysts under ambient conditions exhibits significantly enhanced efficacy in HCHO degradation. The precious metals (e.g., Pt, Au, Pd, Ag and Rh) are often used as catalysts for efficient oxidation at ambient temperature, but the cost is very high. Researchers have also started to explore the non-noble catalysts, such as MnO\u003csub\u003e2\u003c/sub\u003e, Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, and other, which also exhibit more advantages (Dong et al., 2021; Yang et al., 2021; Huang et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Manganese oxides have been increasingly employed for HCHO removal due to their high activity, low toxicity, and ready availability (Zhu et al., 2019). To examine the influence of precursor solution pH on the microstructure and surface characteristics of MnO\u003csub\u003ex\u003c/sub\u003e, a series of experiments were conducted. The results showed that at pH\u0026thinsp;=\u0026thinsp;13, MnO\u003csub\u003ex\u003c/sub\u003e exhibited the largest interlayer spacing, alongside the greatest pore diameter and specific surface area. The distinct structural characteristics promoted the generation of numerous manganese vacancies and catalytically active sites, thereby enhancing ROS sequestration and improving catalytic performance in HCHO oxidation (Zhang et al., 2023). Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e was also a potential candidate for VOCs oxidation (Hua et al.,2023; Wu et al.,2024) owing to its unique spinel structure, multivalent state, abundant reactive oxygen, and superior redox performance. Mg-doped Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e was studied, and the resulting catalyst exhibited enhanced catalytic activity for HCHO oxidation at room temperature due to its defect-enriched structure (Meng et al., 2024). Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e was a comparison of the effect of catalytic oxidation of HCHO over MnO\u003csub\u003e2\u003c/sub\u003e-based catalysts reported previously. Obviously, the traditional MnO\u003csub\u003e2\u003c/sub\u003e-based catalysts were difficult to disintegrate HCHO at ambient temperature, except for precious metal catalysts with high prices.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSummarization of literature data on catalytic oxidation of HCHO over MnO\u003csub\u003ex\u003c/sub\u003e\u0026ndash;based catalysts at low temperature\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCatalyst\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePreparation condition\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTest conditions\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eT\u003c/em\u003e\u003csub\u003e50\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eT\u003c/em\u003e\u003csub\u003e100\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eReferences\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eα-MnO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCalcined at 140 \u003csup\u003eo\u003c/sup\u003eC for 12h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e170 ppm HCHO, GHSV\u0026thinsp;~\u0026thinsp;100,100 mL/g\u0026middot;h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e140\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Bai et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2016\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eβ-MnO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCalcined at 140 \u003csup\u003eo\u003c/sup\u003eC for 12h and dried at 120 \u003csup\u003eo\u003c/sup\u003eC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e170 ppm HCHO, GHSV\u0026thinsp;~\u0026thinsp;100,100 mL/g\u0026middot;h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e180\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Bai et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2016\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMnO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-CeO\u003csub\u003e2\u003c/sub\u003e (MP773)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDried at 110 \u003csup\u003eo\u003c/sup\u003eC for 12h; calcined at 500 ℃for 6 h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e580 ppm HCHO, 18% O\u003csub\u003e2\u003c/sub\u003e, He balance, GHSV\u0026thinsp;~\u0026thinsp;30L/g\u0026middot;h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Tang et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2006\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMnO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-CeO\u003csub\u003e2\u003c/sub\u003e (CeMn80)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDried at 110 \u003csup\u003eo\u003c/sup\u003eC overnight; calcined at 400 \u003csup\u003eo\u003c/sup\u003eC for 6 h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e580 ppm HCHO, 20% O\u003csub\u003e2\u003c/sub\u003e, N\u003csub\u003e2\u003c/sub\u003e balance, GHSV\u0026thinsp;~\u0026thinsp;30L/g\u0026middot;h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Liu et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2009\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePt/MnO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-CeO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDried at 110 \u003csup\u003eo\u003c/sup\u003eC for 12h; calcined at 500 \u003csup\u003eo\u003c/sup\u003eC for 6 h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30 ppm HCHO, 20% O\u003csub\u003e2\u003c/sub\u003e, He balance, GHSV\u0026thinsp;~\u0026thinsp;30L/g\u0026middot;h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eRT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Tang et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2008\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAg/MnO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-CeO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDried at 110 \u003csup\u003eo\u003c/sup\u003eC for 12h; calcined at 500 \u003csup\u003eo\u003c/sup\u003eC for 6 h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e580 ppm HCHO, 18% O\u003csub\u003e2\u003c/sub\u003e, GHSV\u0026thinsp;~\u0026thinsp;30L/g\u0026middot;h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e~\u0026thinsp;80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Tang et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2006\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eNevertheless, these oxides usually show low catalytic activity under high humidity conditions at ambient temperature, so effective strategies are required to improve their efficiency in HCHO decomposition. Therefore, a variety of new materials have been developed for the removal of indoor HCHO, including gas adsorption, gas storage and catalysis. MOFs have attracted considerable attention due to their unique structural characteristics and exceptional functional properties, such as high specific surface areas, inherent porosity, exceptional chemical stability, and accessible metallic sites. One type of UiO-66 derived MOFs catalysts were generated to degrade HCHO under visible light and exhibited a high activity (Duan et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003ea). MnO\u003csub\u003e2\u003c/sub\u003e/UiO-66-NH\u003csub\u003e2\u003c/sub\u003e MOFs nanocomposite were also prepared to remove gas HCHO. The results showed that MnO\u003csub\u003e2\u003c/sub\u003e/UiO-66-NH\u003csub\u003e2\u003c/sub\u003e can effectively remove HCHO at ambient temperature, but increasing the loading of manganese dioxide diminishes its removal efficiency (Vikrant et al., 2022). The solid solution of Mn\u003csub\u003ex\u003c/sub\u003eCo\u003csub\u003e3\u003c/sub\u003e-xO\u003csub\u003e4\u003c/sub\u003e prepared using MOFs with varying Co/Mn molar ratios was reported to display superior catalytic efficiency for oxidation under standard ambient conditions. In summary, various MOFs precursors were synthesized and characterized, and their derived oxide catalysts were evaluated for HCHO degradation under ambient conditions. These findings highlight the promising catalytic potential of MOFs-derived materials in HCHO oxidation at low-temperatures (Tu et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn this study, a series of monometallic and bimetallic MOFs-derived metal oxide catalysts and supported catalysts were synthesized via hydrothermal synthesis and further characterized using X-ray diffraction (XRD), Scanning and transmission electron microscopy (SEM, TEM), H\u003csub\u003e2\u003c/sub\u003e-temperature programmed reduction (H\u003csub\u003e2\u003c/sub\u003e-TPR), NH\u003csub\u003e3\u003c/sub\u003e-temperature programmed desorption (NH\u003csub\u003e3\u003c/sub\u003e-TPD), X-ray spectroscopy (XPS), and electron paramagnetic resonance (EPR). \u003cem\u003eIn situ\u003c/em\u003e diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was utilized to gain a better understanding of the potential mechanism underlying HCHO degradation over MnCe-MOFs catalysts. This research can provide some new insights into efficient methods to eliminate low indoor concentration of HCHO at ambient temperature.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Catalyst preparation\u003c/h2\u003e\u003cp\u003eThe synthesis of MnCe-MOFs catalysts via a hydrothermal process incorporating N, N-dimethylformamide (DMF) was conducted in a series of steps to enable the catalytic degradation of HCHO. First, 4.2g of 1, 3, 5-benzoic acid (H\u003csub\u003e3\u003c/sub\u003e-BTC) were added to 50 mL of DMF solution and stirred until completely dissolved to obtain solution A. Second, 1.45g of Ce(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO and 3.87mL of 50% Mn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e solution were added to 10 mL distilled water and stirred until completely dissolved to obtain solution B. Subsequently, solution B was gradually introduced into solution A under continuous stirring for 15 minutes, followed by transferring the resultant mixture into a Teflon-lined autoclave and maintaining it at 120\u0026deg;C for an 8-hour hydrothermal treatment. After that, the powered products were obtained by centrifugation and washed separately three times with H\u003csub\u003e3\u003c/sub\u003e-BTC and ethanol. The final processing steps involved drying the samples for 5 hours at 80\u0026deg;C, followed by calcination for 3 hours at 500\u0026deg;C. The catalysts synthesized with a Mn:Ce molar ratio of 5:1 were designated as MnCe-MOFs. The studied catalysts, including monometallic MOFs catalysts and supported catalysts (MnCe-MOFs/ZSM-5, MnCe-MOFs/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, and MnCe-MOFs/palygorskite) with various loading amount were all synthesized using the same procedure.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Characterization\u003c/h2\u003e\u003cp\u003eThe crystallographic features of the catalysts were characterized via X-ray diffraction (XRD) analysis (XRD-6100, Bruker, Germany) employing a CuKα radiation-based diffractometer. The measurements were conducted over an angular range of 10\u0026deg;\u0026ndash;80\u0026deg; at a rate of 8\u0026deg; per minute. Morphological examination and high-resolution imaging of the microstructure and crystalline phases were performed using the scanning electron microscope (SEM, Hitachi, Japan) and the transmission electron microscope (TEM, FEI, USA) techniques. Energy dispersive spectroscopy (EDS) was utilized to analyze the elemental composition and map the spatial distribution of active sites, thereby providing insights into their microstructural features. The specific surface area, pore volume, and pore size distribution were analyzed using the BET and BJH model, with data acquired via an ASAP 2460 analyzer (Hitachi, Japan). The redox behavior of the catalyst was investigated via hydrogen temperature-programmed reduction (H\u003csub\u003e2\u003c/sub\u003e-TPR) analysis, enabling the evaluation of its reduction kinetics and active site distribution. The catalyst samples (50 mg) were exposed to an argon gas flow for pretreatment purposes at 300 \u003csup\u003eo\u003c/sup\u003eC for 30 min. After that, a 10% H\u003csub\u003e2\u003c/sub\u003e/Ar mixture flow (30 mL/min) was introduced, and the reactor was heated at a rate of 10 \u003csup\u003eo\u003c/sup\u003eC\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e from environmental temperature to 800 \u003csup\u003eo\u003c/sup\u003eC. The temperature programmed desorption of O\u003csub\u003e2\u003c/sub\u003e (O\u003csub\u003e2\u003c/sub\u003e-TPD) was carried out on the same apparatus as for H\u003csub\u003e2\u003c/sub\u003e-TPR to investigate the location of active oxygen in the catalyst. The measurement was performed over a temperature range of 60\u0026ndash;800℃, with a heating rate of 15 ℃/min. NH\u003csub\u003e3\u003c/sub\u003e temperature programmed desorption (NH\u003csub\u003e3\u003c/sub\u003e-TPD) detected by the TCD was applied to characterize the surface acidity and distribution of acid strengths on the catalyst. Surface-related elemental composition, chemical bonding states, and electronic configurations were characterized using X-ray photoelectron spectroscopy (XPS, Thermo ESCALAB 250XI, USA). An Al Kα radiation source was used with the energy of 1486.8 eV, the tube voltage of 15 kV, and the current of 10 mA, respectively. Additionally, surface unpaired electrons were characterized via electron paramagnetic resonance (EPR) to evaluate the influence of oxygen vacancies on the catalytic material's performance.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Performance evaluation\u003c/h2\u003e\u003cp\u003eUnder conditions simulating an indoor quiet environment, the catalytic oxidation efficacy of the catalysts was assessed using a 0.125 m\u003csup\u003e3\u003c/sup\u003e sealed glass container. First, 1.0 g of MnCe-MOFs powder catalyst was uniformly dispersed across a 90 mm diameter petri dish and positioned at the reactor's base. The starting concentration of HCHO was regulated to 1.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 mg/m\u003csup\u003e3\u003c/sup\u003e by volatilization of HCHO solution and measured by HCHO analyzer (PPM-400st, UK). After that, the reactor was enclosed with a large amount of vaseline to prevent a decrease in HCHO concentration without catalysts. Environmental temperature stabilized at 25\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u0026deg;C, with concentration measurements performed triply every 12 hours. The catalytic oxidation performance of the catalysts was calculated by determining the HCHO degradation rate via Eq.\u0026nbsp;(1):\u003c/p\u003e\u003cp\u003e\u003cem\u003eη\u003c/em\u003e (%)\u0026thinsp;=\u0026thinsp;1-[(\u003cem\u003eC\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e-\u003cem\u003eC\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e)]/\u003cem\u003eC\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e\u0026times;100% (1)\u003c/p\u003e\u003cp\u003ewhere \u003cem\u003eC\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e denotes the initial HCHO concentration; \u003cem\u003eC\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e represents the concentration of gaseous HCHO at time; \u003cem\u003eη\u003c/em\u003e denotes the degradation rate.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Characterization analysis\u003c/h2\u003e\u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\u003ch2\u003e3.1.1. XRD\u003c/h2\u003e\u003cp\u003eThe crystal structures of Mn-MOFs and MnCe-MOFs calcined at 500 \u003csup\u003eo\u003c/sup\u003eC were investigated by XRD. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a), the diffraction peaks at 2θ\u0026thinsp;=\u0026thinsp;18.0\u0026deg;, 28.9\u0026deg;, 32.3\u0026deg;, 36.1\u0026deg;, 38.0\u0026deg;, and 64.7\u0026deg; correspond to the (101), (112), (103), (211), (004) and (400) crystal planes of Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e (PDF#24\u0026ndash;0734), which are attributed to MnO and Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, respectively. The peaks at 2θ\u0026thinsp;=\u0026thinsp;28.5\u0026deg;, 33.1\u0026deg;, 47.5\u0026deg;, 56.3\u0026deg;, 59.1\u0026deg;, 69.4\u0026deg;, 76.7\u0026deg;, and 79.1\u0026deg; correspond to the (111), (200), (220) and (311), (222), (400), (331) and (420) of CeO\u003csub\u003e2\u003c/sub\u003e (PDF#43-1002). Previous studies have demonstrated that the ionic radius of Mn\u003csup\u003e3+\u003c/sup\u003e (0.066 nm) is smaller than that of Ce\u003csup\u003e4+\u003c/sup\u003e (0.094 nm), and the characteristic diffraction peak of Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e in MnCe-MOFs exhibits a weaker intensity compared to Mn-MOFs. This is attributed to the inhibitory effect of CeO\u003csub\u003e2\u003c/sub\u003e on Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e crystal growth (Kan et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), thereby facilitating the incorporation of Mn into the CeO\u003csub\u003e2\u003c/sub\u003e lattice to form a solid solution (Niu et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Sihaib et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe XRD patterns of MnCe-MOFs with different loading amounts supported on ZSM-5 were shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b). The results showed that these MnCe-MOFs/ZSM-5 catalysts were similar, and the intensities of the diffraction peaks of ZSM-5 (PDF#42\u0026ndash;0120), observed at 2θ\u0026thinsp;=\u0026thinsp;13.2\u0026deg;, 13.9\u0026deg;, 14.7\u0026deg;, 23.0\u0026deg;, 23.8\u0026deg;, 29.8\u0026deg;, 44.9\u0026deg;and 45.4\u0026deg;, gradually decreased as MnCe-MOFs loading increased, due to enhanced surface coverage of active components on ZSM-5. As the MnCe-MOFs supporting amount enhanced, the characteristic diffraction peaks at 2θ\u0026thinsp;=\u0026thinsp;28.5\u0026deg;, 47.4\u0026deg;, and 36.1\u0026deg; could be detected in this sample, indicating the creation of a solid solution phase comprising manganese and cerium oxide constituents. The above result also demonstrated that the crystal size increased with the enhancing supporting amount, which was also beneficial for the improvement of HCHO degradation, but the oxidation rate decreased.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eCompared to conventional MnOx-CeO\u003csub\u003e2\u003c/sub\u003e composites requiring complex synthesis or high Mn:Ce ratios (Miao et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), our MnCe-MOFs achieved atomic-level mixing of Mn and Ce via a single-step hydrothermal method (Mn:Ce\u0026thinsp;=\u0026thinsp;5:1). This structural homogeneity, evidenced by EPR and H\u003csub\u003e2\u003c/sub\u003e-TPR, facilitated abundant oxygen vacancies and enhanced oxygen mobility. MOFs-derived materials retain the highly ordered porous structures and ultrahigh surface areas from their MOFs precursors, facilitating efficient mass transfer and abundant exposure of active site. For example, MnCe-MOFs demonstrated a specific surface area of 370.48 m\u0026sup2;/g (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), far exceeding typical metal oxides like MnO\u003csub\u003e2\u003c/sub\u003e (Zhang et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This structural advantage facilitates enhanced adsorption and catalytic degradation of HCHO at ambient temperature.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e3.1.2. BET\u003c/h2\u003e\u003cp\u003eTo examine the influence of support material and loading quantity on catalysts' specific surface area and pore dimensions, BET measurements were conducted on representative samples (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The specific surface area and pore dimensions of MnCe-MOFs/ZSM-5 catalysts decreased with increasing MnCe-MOFs loading, possibly due to the successful dispersion of MnCe-MOFs active components on the high-surface-area and low-pore-size ZSM-5 support. The findings further revealed that catalytic performance was influenced by parameters beyond surface area characteristics, with the MnCe-MOFs active component serving as a critical contributor to its functionality. However, compared to ZSM-5, the MnCe-MOFs supported on Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and palygorskite exhibited lower surface area and larger pore size, which was not conducive to improved performance, as the support materials failed to provide sufficient active site for enhanced adsorption and oxidation. The BET results indicated that ZSM-5 was superior to Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and palygorskite as a support due to its porous structure, which facilitates the diffusion of HCHO molecules and enhance contact between HCHO and the active sites, thereby facilitating HCHO oxidation at ambient temperature.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\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\u003eSpecific surface area, pore volume and size of these catalysts\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\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\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSamples\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSpecific surface area (m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePore volume (cm\u003csup\u003e3\u003c/sup\u003e/g)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAverage aperture (nm)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMnCe-MOFs/ZSM-5 (2%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e370.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e5.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMnCe-MOFs/ZSM-5 (40%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e263.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMnCe-MOFs/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (40%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e29.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e12.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMnCe-MOFs/palygorskite (40%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e53.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e10.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a), the MnCe-MOFs-500/ZSM-5 catalyst exhibits a Type IV-type isotherm (Thommes et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and shows a significant increase in adsorption due to capillary condensation in the moderate relative pressure region (\u003cem\u003ep\u003c/em\u003e/\u003cem\u003ep\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;~\u0026thinsp;0.4\u0026thinsp;\u0026minus;\u0026thinsp;0.8). The desorption branch presents a H4-type hysteresis loop at \u003cem\u003ep\u003c/em\u003e/\u003cem\u003ep\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;~\u0026thinsp;0.4\u0026thinsp;\u0026minus;\u0026thinsp;0.5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a)). According to IUPAC classification, the Type IV-type isotherm indicates a mesoporous structure (2\u0026ndash;50 nm), while the H4-type hysteresis loop suggests the microporous-mesoporous composite pore characteristics, such as the synergistic interaction between micropores in the ZSM-5 support and mesopores in the MnCe-MOFs active components. This interpretation aligns with the pore size distribution results (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b)).\u003c/p\u003e\u003cp\u003eThe MnCe-MOFs catalysts loaded on Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and palygorskite also exhibit Type IV-type isotherms, but accompanied by H3-type hysteresis loops (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a)). According to IUPAC definitions, H3 hysteresis loops are typically associated with non-rigid layered particle aggregation structures or open mesopores. In conjunction with its BET data (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), the low specific surface area (29.21 m\u003csup\u003e2\u003c/sup\u003e/g) and large average pore size (12.7 nm) of MnCe-MOFs/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e indicate that the active components primarily cover the surface of the support, forming a loosely packed mesoporous structure. The broad pore size distribution (10.8 nm) of MnCe-MOFs/palygorskite, however, aligns with the interlayer pore characteristics of natural fibrous clay supports. Additionally, commercially available ZSM-5, due to its well-defined microporous framework (pore size\u0026thinsp;\u0026lt;\u0026thinsp;2 nm) and high specific surface area (370.5 m\u003csup\u003e2\u003c/sup\u003e/g), can provide abundant anchoring sites for MnCe-MOFs, promoting uniform dispersion of active components and forming micro-porous-mesoporous composite channels, thereby optimizing the diffusion and oxidation performance of HCHO molecules.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e3.1.3. SEM and TEM\u003c/h2\u003e\u003cp\u003eThe relationship between compositional variations and the microstructural properties of the catalysts, including their morphological features, was systematically analyzed. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e exhibited the SEM and TEM images of Mn-MOFs (a, b, c, d) and MnCe-MOFs (e, f, g, h). Mn-MOFs calcined at 500 \u003csup\u003eo\u003c/sup\u003eC displayed a large interlayer void, a disrupted skeleton, and a relatively rough surface morphology, with numerous spherical Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles, which facilitated the catalytic reaction. However, compared to Mn-MOFs, MnCe-MOFs exhibited an abundant surface structure with more uniformly loose spherical nanoparticles composed of CeO\u003csub\u003e2\u003c/sub\u003e and Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, which was beneficial for improving performance. Meanwhile, crystal structures of Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e and CeO\u003csub\u003e2\u003c/sub\u003e, exhibiting lattice fringes of 0.25 nm and 0.31 nm, corresponding to (2 1 1) and (1 1 1) planes, were observed on the main exposed surface of Mn-MOFs and MnCe-MOFs, respectively, in agreement with the XRD results. Moreover, some amorphous metal oxides can be observed in the MnCe-MOFs, which is attributed to the ability of cerium oxide to inhibit the growth of manganese oxide crystals, and to the synergistic effects of bimetallic Mn-Ce oxiders; both factors contribute to improving oxidative activity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo evaluate the spatial dispersion of elements in Mn-MOFs catalysts and MnCe-MOFs catalysts, the Mn, Ce and O elemental mapping was performed in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The analysis showed an even distribution of Mn and O components on the Mn-MOFs surface, suggesting their integration into the Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e lattice structure. Meanwhile, the Mn, Ce and O also dispersed homogeneously on the surface of MnCe-MOFs. Furthermore, the low content of Ce was highly dispersed owing to the uniform self-assembly arrangement, providing the potential synergism with manganese oxide to enhance electron transfer efficiency and improve active site availability, thereby boosting HCHO oxidation performance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e3.1.4. H\u003csub\u003e2\u003c/sub\u003e-TPR\u003c/h2\u003e\u003cp\u003eThe reducibility of the Mn-MOFs, Ce-MOFs, and MnCe-MOFs catalysts was determined by H\u003csub\u003e2\u003c/sub\u003e-TPR (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The peak observed at 250\u0026deg;C in Mn-MOFs was attributed to the reduction of MnO\u003csub\u003e2\u003c/sub\u003e/Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e to Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, while the peak at 359\u0026deg;C corresponded to the reduction of Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e to MnO (Hu et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The Mn-MOFs sample exhibited remarkable low-temperature reduction capability, attributed to the coexisting valence states of manganese and the dynamic behavior of oxygen species, which collectively contributed to its enhanced catalytic performance toward HCHO oxidation under ambient conditions. However, no reduction peak was observed in the Ce-MOFs due to their low redox performance at low temperatures. While Ce was introduced into Mn-MOFs and derived the bimetal mixed oxide, the reduction peak shifted to lower temperatures, indicating an increase in oxygen fluidity (Azalim et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Quiroz et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Therefore, MnCe-MOFs exhibited significantly enhanced redox performance, and the two reduction temperatures were reduced by 11 \u003csup\u003eo\u003c/sup\u003eC, attributed to the synergism of Mn and Ce, which reduced the bonding energy between cations and oxygen ions while enhancing oxygen mobility (Venkataswamy et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The lower temperature of H\u003csub\u003e2\u003c/sub\u003e reduction for MnCe-MOFs implied the higher oxygen mobility participated in the oxidation reaction, which was conducive to the removal of HCHO at ambient temperature.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e3.1.5. O\u003csub\u003e2\u003c/sub\u003e-TPD analysis\u003c/h2\u003e\u003cp\u003eResearch has shown that in transition metal oxides, oxygen typically desorbs in three distinct temperature zones: molecular adsorbed oxygen (O\u003csub\u003e2\u003c/sub\u003e) at 50 to 350℃, atomic adsorbed oxygen (O-) at 350 to 750℃, and lattice oxygen (O\u003csub\u003e2\u0026minus;\u003c/sub\u003e) at temperatures above 750℃. Among these, adsorbed oxygen is more prone to desorption compared to lattice oxygen (Bai et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Bai et al., 2014). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the MnCe-MOFs/ZSM-5 catalyst shows two smaller peaks at 95\u0026deg;C and 125\u0026deg;C, which likely correspond to the desorption of physically adsorbed O\u003csub\u003e2\u003c/sub\u003e molecules. Peaks at 336\u0026deg;C, 546\u0026deg;C, and 676\u0026deg;C might correspond to the desorption of chemically adsorbed atomic oxygen (O\u003csup\u003e\u0026minus;\u003c/sup\u003e). These peaks suggest that the MnCe-MOFs/ZSM-5 catalyst surface contains a significant amount of active oxygen species, which desorb at lower temperatures, indicating their potential role in catalytic reactions. Compared to Mn-MOFs and MnCe-MOFs catalysts, MnCe-MOFs/ZSM-5 exhibits oxygen species desorption peaks at lower temperatures (e.g., 95\u0026deg;C and 125\u0026deg;C), suggesting a higher concentration of active oxygen species on its surface, which may facilitate the oxidation of HCHO. Although MnCe-MOFs also shows a low desorption temperature, it may not have as rich or active oxygen species as MnCe-MOFs/ZSM-5. The higher desorption temperature of Mn-MOFs may result in lower participation of active oxygen species at room temperature, thereby affecting its catalytic performance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\u003ch2\u003e3.1.6. NH\u003csub\u003e3\u003c/sub\u003e-TPD analysis\u003c/h2\u003e\u003cp\u003eStudies have demonstrated that the catalyst's acidic properties are critical to affect the oxidation process of VOCs, and that the C-H bond is broken at these acidic sites. First, weak acid sites enhance the adsorption of HCHO molecules on the catalyst surface through hydrogen bonding or electrostatic interactions, bringing them closer to active redox sites, such as Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e/Ce\u003csup\u003e4+\u003c/sup\u003e. This reduces the activation energy of C-H bonds and accelerates subsequent oxidation reactions (Huang et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Second, the acidity of weak acid sites is moderate, allowing for effective promotion of C-H bond cleavage in HCHO through proton H\u003csup\u003e+\u003c/sup\u003e transfer, generating intermediate products (Quiroz et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). This also avoids the excessive adsorption or accumulation of intermediates caused by strong acid sites. Additionally, the interaction between weak acid sites and surface hydroxyl groups (-OH) or reactive oxygen species (e.g., \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{O}_{2}^{-}\\)\u003c/span\u003e\u003c/span\u003e and \u0026bull;OH) enhances the stability of these reactive oxygen species (Zhang et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), enabling their continuous participation in the deep oxidation of HCHO, ultimately converting it into CO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO.\u003c/p\u003e\u003cp\u003eTo explore the relationship between the surface acidity of MnCe-MOFs loaded on different supporters and their activity, NH\u003csub\u003e3\u003c/sub\u003e-TPD analysis were conducted (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Three types of catalysts showed desorption peaks at 122 \u003csup\u003eo\u003c/sup\u003eC, 114 \u003csup\u003eo\u003c/sup\u003eC and 95 \u003csup\u003eo\u003c/sup\u003eC in the weak acid region, respectively. The result indicated that MnCe-MOFs/ZSM-5 displayed the highest weak acidity and lowest desorption peak temperature, which was beneficial for improving oxidation performance. Meanwhile, the medium and strong acidity levels of MnCe-MOFs/ZSM-5 and MnCe-MOFs/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e were relatively low, whereas MnCe-MOFs/palygorskite exhibited increased acidity, especially in the strong acid region, which was detrimental to the optimal performance. The above results demonstrated that the MnCe-MOFs loaded on different supporters exhibited varying acidity, which in turn led to differences in oxidation properties, mainly due to the presence of weak acid sites. Leveraging the high specific surface area and ordered pore structure of the ZSM-5 support, the presence of weak acid sites further improves the contact efficiency between HCHO molecules and active components, thereby synergistically enhancing the catalyst\u0026rsquo;s oxidation activity and cycling performance. Ultimately, this results in excellent catalytic effects of MnCe-MOFs/ZSM-5 in the degradation of HCHO at low concentrations and room temperature.\u003c/p\u003e\u003cp\u003eSupported MnO\u003csub\u003e2\u003c/sub\u003e catalysts show limited stability due to weak metal-support interactions (Miao et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). ZSM-5 high surface area (370 m\u003csup\u003e2\u003c/sup\u003e/g) and weak acid sites promote HCHO adsorption and intermediate oxidation, while the MOFs-derived active components prevent aggregation, ensuring long-term stability.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\u003ch2\u003e3.1.7. XPS\u003c/h2\u003e\u003cp\u003eTo further quantify the chemical state of the surface elements of Mn-MOFs catalysts and MnCe-MOFs catalysts, the binding energies of Mn 2p, Ce 3d and O 1s were analyzed by XPS (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). The Mn 2p spectrum divided into Mn 2p\u003csub\u003e3/2\u003c/sub\u003e and Mn 2p\u003csub\u003e1/2\u003c/sub\u003e with the binding energies at 641.7 eV and 653.3 eV, respectively. The Mn 2p\u003csub\u003e3/2\u003c/sub\u003e XPS peaks were decomposed into three distinct peaks at binding energies of 640.2 eV, 641.8 eV, and 644.2 eV, corresponding to Mn\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e3+\u003c/sup\u003e and Mn\u003csup\u003e4+\u003c/sup\u003e, respectively. This confirmed the presence of mixed valence states in Mn, with a Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e ratio of 1.06 calculated based on peak area integration. The coexistence of manganese in diverse valence states can enhance the generation of abundant oxygen vacancy sites and surface undercoordinated bonds, thereby accelerating the oxidation reaction kinetics (Yang et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). While the characteristic peak areas of Mn decreased, the Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e ratio also dropped from 1.06 to 0.99, suggesting an elevated Mn\u003csup\u003e4+\u003c/sup\u003e concentration in MnCe-MOFs as a result of Ce incorporation.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(b) showed the Ce 3d XPS spectra of MnCe-MOFs, which can be divided into peaks at 882.4 eV, 888.7 eV, 898.3 eV, 900.9 eV, 907.3 eV, and 916.7 eV corresponding to Ce\u003csup\u003e4+\u003c/sup\u003e, and at 884.6 eV and 903.2 eV assigned to Ce\u003csup\u003e3+\u003c/sup\u003e. The presence of Ce\u003csup\u003e3+\u003c/sup\u003e also induced the charge imbalance, generating unsaturated chemical bonds and oxygen vacancies, and these lattice oxygen storage and transfer between Ce\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e4+\u003c/sup\u003e was conducive to the oxidation reaction (Zhang et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(c) shows the O 1s XPS spectra of Mn-MOFs and MnCe-MOFs, which can be deconvoluted into two peaks at binding energies of 531.3 eV and 529.7 eV, corresponding to surface oxygen species (\u003cem\u003eO\u003c/em\u003e\u003csub\u003esur\u003c/sub\u003e) and lattice oxygen (\u003cem\u003eO\u003c/em\u003e\u003csub\u003elatt\u003c/sub\u003e), respectively. The conversion pathways of oxygen were usually O\u003csub\u003e2\u003c/sub\u003e(sur)\u0026rarr; O\u003csup\u003e2\u0026minus;\u003c/sup\u003e(sur) \u0026rarr; O\u003csup\u003e\u0026minus;\u003c/sup\u003e(sur) \u0026rarr; O\u003csup\u003e2\u0026minus;\u003c/sup\u003e(lat). \u003cem\u003eO\u003c/em\u003e\u003csub\u003esur\u003c/sub\u003e was found to participate in oxidation reactions, and higher concentrations of \u003cem\u003eO\u003c/em\u003e\u003csub\u003esur\u003c/sub\u003e enhanced oxidation activity, while a high concentration of \u003cem\u003eO\u003c/em\u003e\u003csub\u003elat\u003c/sub\u003e facilitated C-H bond cleavage (Liu et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The results exhibited that \u003cem\u003eO\u003c/em\u003e\u003csub\u003esur\u003c/sub\u003e could quickly transfer and replenish the consumed \u003cem\u003eO\u003c/em\u003e\u003csub\u003elat\u003c/sub\u003e to maintain the oxygen balance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\u003ch2\u003e3.1.8. EPR\u003c/h2\u003e\u003cp\u003eTo detect the oxygen vacancies of the sample, an EPR test was performed (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e). A g\u0026thinsp;=\u0026thinsp;2.003 signal was detected in all samples, because of oxygen vacancies in the material (Zhao et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zhou et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Oxygen vacancy signals exhibited a descending intensity sequence: MnCe-MOFs/ZSM-5\u0026thinsp;\u0026gt;\u0026thinsp;MnCe-MOFs/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;MnCe-MOFs\u0026thinsp;\u0026gt;\u0026thinsp;Mn-MOFs, which indicates that the interaction between MnCe-MOFs and ZSM-5 carriers result in more oxygen vacancies, while MOFs materials without loading form fewer oxygen vacancies than their loaded counterparts. Oxygen vacancy as an electron enrichment facilitates O\u003csub\u003e2\u003c/sub\u003e adsorption, activation and formation of superoxide radical (\u0026bull;\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{O}_{2}^{-}\\)\u003c/span\u003e\u003c/span\u003e) or lattice oxygen (O\u003csup\u003e\u0026minus;\u003c/sup\u003e), which directly participates in the deep oxidation of HCHO (HCHO\u0026rarr;CO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO) (Huang et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Hence, MnCe-MOFs/ZSM-5 demonstrates superior catalytic performance.\u003c/p\u003e\u003cp\u003eWhile composite catalysts (MnOx-CeO\u003csub\u003e2\u003c/sub\u003e) enhance activity through Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e/Ce\u003csup\u003e4+\u003c/sup\u003e redox cycles, such composites typically require high Mn:Ce ratios or complex synthesis methods (Miao et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Our MnCe-MOFs derive from a single-step hydrothermal process with a Mn:Ce ratio of 5:1. As shown in EPR patterns, the MOFs structure ensures atomic-level mixing of Mn and Ce, creating abundant oxygen vacancies and facilitating O\u003csub\u003e2\u003c/sub\u003e activation. Meanwhile, H\u003csub\u003e2\u003c/sub\u003e-TPR confirms a 50℃ reduction in peak temperature for MnCe-MOFs compared to Mn-MOFs, indicating enhanced oxygen mobility.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Catalyst performance evaluation\u003c/h2\u003e\u003cp\u003eThe oxidation activities of these monometallic oxides, bimetallic oxides, and supported catalysts were all evaluated by a low concentration of HCHO under ambient temperature. The activities of these MOFs catalysts, composed of six different types of monometallic oxides, were evaluated for HCHO degradation (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e). These catalysts displayed significant differences in oxidation according to the different property of these monometallic oxides. Among them, Mn-MOFs catalysts exhibited the highest activities for HCHO oxidation. HCHO concentration was reduced from 1.062 mg/m\u003csup\u003e3\u003c/sup\u003e to 0.008 mg/m\u003csup\u003e3\u003c/sup\u003e within 48 h, and a 99.3% degradation rate was achieved due to the unique structure of MOFs, their lower H\u003csub\u003e2\u003c/sub\u003e reduction peak temperature, and the presence of multiple manganese valence states. Although Cu-MOFs exhibited a larger H\u003csub\u003e2\u003c/sub\u003e reduction peak area at 269 \u003csup\u003eo\u003c/sup\u003eC, it showed the lowest removal rate of 14.0% in these samples. The order of HCHO degradation among these samples was observed as follows: Cu-MOFs\u0026thinsp;\u0026lt;\u0026thinsp;Co-MOFs\u0026thinsp;\u0026lt;\u0026thinsp;Fe-MOFs\u0026thinsp;\u0026asymp;\u0026thinsp;Ce-MOFs\u0026thinsp;\u0026lt;\u0026thinsp;Cr-MOFs\u0026thinsp;\u0026lt;\u0026thinsp;Mn-MOFs.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAlthough Mn-MOFs had the optimum oxidation performance, the degradation rate decreased from 99.3% to 82.6% after five cycles of experiments with a poor stability, which may be attributed to the poor ability of water vapor resistance. Therefore, the performances of MOFs-derived bimetallic oxides (MnFe-MOFs, MnCu-MOFs, MnCo-MOFs, MnCr-MOFs, and MnCe-MOFs) for HCHO degradation were investigated and are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e to evaluate their effectiveness in enhancing stability. The result exhibited that the oxidation activities of these MOFs-derived bimetallic oxides were all lower than Mn-MOFs. Among them, the MnCe-MOFs and MnCu-MOFs showed the highest (96.3%) and lowest (81.7%) degradation efficiency, respectively. Then, five cycles of experiments demonstrated that the degradation rate of HCHO consistently remained above 96% using MnCu-MOFs catalysts. Mn-MOFs degraded to 82.6% due to poor water resistance (Huang et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). This stability is attributed to hydrophobic MOFs frameworks and robust metal-oxide interactions. Meanwhile, the level of HCHO was below the regulatory limit (0.08 mg/m\u003csup\u003e3\u003c/sup\u003e) at 48 h, indicating that the cerium oxide doping could improve the stability of the MOFs-derived monometallic oxides.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo evaluate the influence of support materials on the catalytic oxidation performance of MnCe-MOFs-based catalysts, ZSM-5, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, and palygorskite powder were selected to support MnCe-MOFs active components (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e). The performances of these catalysts, each containing 40% MnCe-MOFs support, show only subtle difference, yet all exhibited excellent performance owing to the active components of MnCe-MOFs. Among the catalysts tested, MnCe-MOFs/ZSM-5 demonstrated the highest catalytic activity, attributed to ZSM-5's high surface area and abundant weak acid sites. The HCHO concentration was reduced from 1.038 mg/m\u003csup\u003e3\u003c/sup\u003e to 0.04 mg/m\u003csup\u003e3\u003c/sup\u003e within 48 h, and the degradation rate reached 96.2% using MnCe-MOFs/ZSM-5 at ambient temperature.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo further enhance performance and reduce costs, the study examined the effect of the loading amount of MnCe-MOFs/ZSM-5 on oxidation activities (Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e(a)). The activities significantly decreased with the reduction in the amount of supported MnCe-MOFs active components. The HCHO removal rate declined from 96.2% to 57.6% as the MnCe-MOFs loading decreased from 40% to 2%. MOFs allow precise control over metal ratios and organic linkers, enabling customized active sites. By optimizing the ZSM-5 loading, MnCe-MOFs/ZSM-5 achieved 93.4% degradation rate of HCHO, a performance that is difficult to attain with conventional oxides (Huang et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAccording to the above results, the stability experiments of MnCe-MOFs/ZSM (20%) were conducted (Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e(b)). The activity remains nearly constant in the five consecutive cycles of experiments, and the degradation rates of HCHO were 93.4%, 92.7%, 92.8%, 93.2% and 93.1% at 48 h, respectively. Therefore, it demonstrated that the MnCe-MOFs/ZSM-5 (20%) was a kind of excellent catalysts for HCHO degradation at ambient temperature in indoor environment.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Reaction mechanism\u003c/h2\u003e\u003cp\u003eTo elucidate the HCHO oxidation mechanism, operando infrared spectroscopy was employed to analyze the redox behavior of MnCe-MOFs under HCHO/N\u003csub\u003e2\u003c/sub\u003e and HCHO/O\u003csub\u003e2\u003c/sub\u003e atmospheres at ambient temperature (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The findings revealed comparable vibrational peak positions between HCHO/N\u003csub\u003e2\u003c/sub\u003e and HCHO/O\u003csub\u003e2\u003c/sub\u003e environments, though spectral intensities exhibited distinct variations. The peaks at 3710 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1660 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were assigned to the bending vibration of H\u003csub\u003e2\u003c/sub\u003eO and the hydroxyl group that is adsorbed on the surface. The peak at 3660 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to the stretching vibration model \u003cem\u003eν\u003c/em\u003e(OH) of the structural hydroxyl group, and its intensity gradually decreased over time in HCHO/N\u003csub\u003e2\u003c/sub\u003e, while remaining stable in HCHO/O\u003csub\u003e2\u003c/sub\u003e, indicating that hydroxyl (OH) groups were consumed during HCHO oxidation in HCHO/N\u003csub\u003e2\u003c/sub\u003e and replenished in HCHO/O\u003csub\u003e2\u003c/sub\u003e. The broad absorption band observed at 3480 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to an overlapping signal originating from hydrogen-bonding interactions, as well as the in-phase and out-of-phase stretching vibrations of H\u003csub\u003e2\u003c/sub\u003eO molecules. This indicates water generation during HCHO oxidation, which subsequently facilitates HCHO adsorption and dissociation on the catalyst surface. The absorption peak at 3240 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the C-H stretching vibration ν (CH) of format, while the peaks at 2840 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1060 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are assigned to the CH stretching vibration ν (CH) and CO stretching vibration ν (CO), respectively, originating from dioxymethylene (DOM), which is the primary intermediate in the HCHO oxidation process. The data revealed a progressive attenuation of DOM intensity under HCHO/N\u003csub\u003e2\u003c/sub\u003e conditions, whereas its enhancement was observed in HCHO/O\u003csub\u003e2\u003c/sub\u003e environment. This implies that the presence of oxygen leads to the generation of reactive oxygen species (ROS) on the catalyst surface, thereby facilitating the oxidative decomposition of HCHO. Concurrently, the peak at 2340 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to CO\u003csub\u003e2\u003c/sub\u003e adsorption, indicating that CO\u003csub\u003e2\u003c/sub\u003e is the terminal oxidation product of HCHO. The peaks at 1560cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1460 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 1360 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to COO asymmetric stretching vibration \u003cem\u003eν\u003c/em\u003e(COO), CH bending vibration \u003cem\u003eδ\u003c/em\u003e(CH), and COO symmetric stretching vibration \u003cem\u003eν\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e(COO), respectively. Based on the above activity and characterization analysis results, the proposed mechanism of MnCe-MOF catalysts for formaldehyde oxidation is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eHCHO is adsorbed onto the catalyst surface through hydrogen bonding interactions, while O₂ undergoes dissociation to reactive oxygen species and surface hydroxyl group during the initial reaction stages. Then, these HCHO molecules participated in the redox reaction with these MnO\u003csub\u003ex\u003c/sub\u003e and CeO\u003csub\u003e2\u003c/sub\u003e active components under active oxygen species and surface hydroxyl group. Meanwhile, the intermediate products of dioxymethylene (DOM), formate and else produced and then further oxidized to carbonic acid under the action of lattice oxygen, which was unstable and quickly decompose into CO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO. Simultaneously, there was a mutual promotion between Mn\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e and CeO\u003csub\u003e2\u003c/sub\u003e, which could achieve oxygen transfer through the change of Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e and Ce\u003csup\u003e4+\u003c/sup\u003e/Ce\u003csup\u003e3+\u003c/sup\u003e valence states, leading to abundant oxygen vacancy sites and diverse oxygen species, which facilitated the catalytic oxidation of formaldehyde over MnCe-MOF catalysts.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this study, a series of novel metal-organic frameworks (MOFs)-based catalysts, including monometallic, bimetallic oxide, and supported catalysts with varied carriers, were synthesized via the hydrothermal method and evaluated for their catalytic oxidation performance toward HCHO degradation at ambient temperature. The results exhibited that the Mn-MOFs, MnCe-MOFs, and MnCe-MOFs/ZSM-5 displayed over 95% HCHO degradation rates at 48h, attributed to reactive oxygen species (ROS, O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e and \u0026middot;OH) instead of physical adsorption. Meanwhile, compared to the Mn-MOFs, their stability and reaction mechanism were analyzed. The results demonstrated that MnCe-MOFs exhibited significantly higher stability due to their excellent resistance to water vapor and the cooperation of Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e and Ce\u003csup\u003e4+\u003c/sup\u003e/Ce\u003csup\u003e3+\u003c/sup\u003e valence states. As for supported catalysts, MnCe-MOFs/ZSM-5 prepared with 20 wt% supporting amount displayed a high oxidation activity (93.4%) and optimal cost-effectiveness, attributed to the synergistic effects of MnCe-MOFs active components and the favorable surface properties (including weak acidity, high surface area, abundant oxygen vacancies) provided by the ZSM-5 support, demonstrating good stability for HCHO oxidation.\u003c/p\u003e"},{"header":"Abbreviations","content":" \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 179px;\"\u003e\n \u003cp\u003eformaldehyde\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003eHCHO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 181px;\"\u003e\n \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003e-temperature programmed reduction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 100px;\"\u003e\n \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003e-TPR\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 179px;\"\u003e\n \u003cp\u003emetal organic frameworks\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003eMOFs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 181px;\"\u003e\n \u003cp\u003eNH\u003csub\u003e3\u003c/sub\u003e-temperature programmed desorption\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 100px;\"\u003e\n \u003cp\u003eNH\u003csub\u003e3\u003c/sub\u003e-TPD\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 179px;\"\u003e\n \u003cp\u003eElectron paramagnetic resonance\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003eEPR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 181px;\"\u003e\n \u003cp\u003eX-ray spectroscopy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 100px;\"\u003e\n \u003cp\u003eXPS\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 179px;\"\u003e\n \u003cp\u003eX-ray diffraction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003eXRD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 181px;\"\u003e\n \u003cp\u003eIn situ diffuse reflectance infrared Fourier transform spectroscopy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 100px;\"\u003e\n \u003cp\u003eDRIFTS\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 179px;\"\u003e\n \u003cp\u003eScanning electron microscopy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003eSEM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 181px;\"\u003e\n \u003cp\u003eN, N-dimethylformamide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 100px;\"\u003e\n \u003cp\u003eDMF\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 179px;\"\u003e\n \u003cp\u003etransmission electron microscopy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003eTEM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 181px;\"\u003e\n \u003cp\u003edioxymethylene\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 100px;\"\u003e\n \u003cp\u003eDOM\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 179px;\"\u003e\n \u003cp\u003e1, 3, 5-benzoic acid\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003eH\u003csub\u003e3\u003c/sub\u003e-BTC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 181px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 100px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis manuscript does not involve human tissue or related experiments.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work; there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the work. Zisu Yang, Qiong Huang, Tao Tao and Mindong Chen were involved in conceptualization. Zisu Yang, Xi Tong, Jia-xin Shan, Qiong Huang and Mindong Chen contributed to methodology. Zisu Yang, Xi Tong, Jia-xin Shan, Jun-jie Mao, Chen Wei, Dawei Li and Bo Yang involved in formal analysis. Zisu Yang, Xi Tong, Jia-xin Shan and Dawei Li involved in data curation. Zisu Yang and Qiong Huang wrote the original draft.\u0026nbsp;Tao Tao, Hong Yang and Bing Li completed language modification.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by Natural Science Foundation of Jiangsu Province (No. BK20201389, BK20190786, and BK20170954), the National Natural Science Foundation of China (No. 21501097 and 51902166), the Postgraduate Research \u0026amp; Practice Innovation Program of Jiangsu Province (KYCX23-1384), the Qing Lan Project of the Jiangsu Higher Education Institutions, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and NUIST-Reading Research Institute Pump-Priming Project.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe\u0026nbsp;authors\u0026nbsp;confirm\u0026nbsp;that\u0026nbsp;the\u0026nbsp;data\u0026nbsp;supporting\u0026nbsp;the\u0026nbsp;findings\u0026nbsp;of\u0026nbsp;this\u0026nbsp;study\u0026nbsp;are\u0026nbsp;available\u0026nbsp;within\u0026nbsp;the\u0026nbsp;article\u0026nbsp;or\u0026nbsp;as\u0026nbsp;its\u0026nbsp;supplementary\u0026nbsp;materials.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll individuals who have contributed to this article have been included in the co-authors.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eS. 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Chinese Chemical Letters. 2023, 34 (3): 107605, https://doi.org/10.1016/j.cclet.2022.06.028.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Metal organic frameworks, HCHO, Catalysts, Catalytic oxidation at ambient temperature","lastPublishedDoi":"10.21203/rs.3.rs-7582325/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7582325/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eReducing airborne formaldehyde (HCHO) to the indoor environmental standard (0.08 mg/m\u003csup\u003e3\u003c/sup\u003e) remains challenging when relying solely on physical adsorption. Ambient-temperature catalytic oxidation offers an effective alternative, decomposing HCHO into CO\u003csub\u003e2\u003c/sub\u003e using high performance transition metal oxides. New type metal organic frameworks (MOFs) of monometallic, bimetallic oxides and supported catalysts with different carriers synthesized by the hydrothermal method were investigated in this study. 1.0 g of catalyst powder was dispersed uniformly on the petri dish (Φ=90 mm) and the initial concentration of HCHO was regulated to 1.0±0.5 mg/m\u003csup\u003e3\u003c/sup\u003e. The reaction temperature was set to ambient temperature (25±5°C), and the measurements for HCHO concentration were performed triply every 12 h. Among them, MnCe-MOFs displayed a high degradation rate (96.3%) at 48 h, with notable stability attributed to the synergistic redox cycling of Ce\u003csup\u003e4+\u003c/sup\u003e/Ce\u003csup\u003e3+\u003c/sup\u003e and Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e, which generated abundant reactive oxygen species (ROS, O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e and ·OH), along with their excellent hydrophobicity. Electron paramagnetic resonance (EPR) analysis revealed that oxygen-deficient sites facilitate the complete oxidation of HCHO. As for supported catalysts, 20wt%MnCe-MOFs/ZSM-5 also exhibited a high oxidation activity (93.4%) ascribed to abundant active components of MnCe-MOFs, surface week acid sites, high surface areas, and abundant oxygen vacancies, indicating high stability for HCHO oxidation.\u003c/p\u003e","manuscriptTitle":"A strategy to improve the performance of MnCe-MOFs/ZSM-5 for formaldehyde degradation at ambient temperature","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-23 15:41:19","doi":"10.21203/rs.3.rs-7582325/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"48d9cff4-eed3-48cd-b5be-a5555340090c","owner":[],"postedDate":"September 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-12T21:53:28+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-23 15:41:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7582325","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7582325","identity":"rs-7582325","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}