Herein, Pd/UiO-66(Ce) catalysts were successfully synthesized by N2H4, H2, and NaBH4 reduction methods with UiO-66(Ce) as support. The best catalyst was selected via utilizing o-xylene as the probe molecule, and its degradation performance of mixed VOCs was further investigated. It was found that the reduction methods greatly influenced the size of Pd nanoparticles, the state of surface Pd, and the support structure in the catalysts, which in turn affected their catalytic performance. Among them, Pd/UiO-66(Ce)-Na exhibited the best o-xylene degradation activity (T90 = 192 degrees C) due to its smaller average Pd particle size (Pd Average = 2.93 nm) and higher surface Pd0 content (Pd0/Pdtotal = 0.79). The performance and interaction of Pd/UiO-66(Ce)-Na catalyst for degradation of mixed VOCs (o-xylene and toluene/benzene) were investigated by DFT adsorption energy calculation, in situ DRIFTS and GC-MS. Results suggested that the single adsorption energy of o-xylene was -1.20 eV, while in the system with toluene/benzene, the adsorption energy decreased to -0.78 and -0.6 eV, respectively. This showed the competitive adsorption effect between benzene and o-xylene was stronger than that between benzene and o-xylene. Finally, combined with in situ DRIFTS and GC-MS, the degradation path of mixed components was analyzed and studied systematically, and the mechanism of intermolecular interaction of benzene in the degradation process of mixed components was further revealed.

Phthalic acid esters (PAEs), ubiquitous semi-volatile organic compounds (SVOCs) in indoor environments, pose adverse effects on human health. However, their degradation mechanisms and pathways remain unclear. Herein, we developed an efficient photothermal catalyst by introducing defects (oxygen vacancies, OVs) on TiO2 (P25) surfaces via electron beam irradiation technology with different irradiation doses (100, 300, 500, and 700 kGy). The TiO2 with defects was employed as a support to prepare Pt-TiO2 catalysts for the photothermal degradation of di (2-ethylhexyl) phthalate (DEMP) and dimethyl phthalate (DMP), two representative PAEs. TiO2 pre-treated with a 300 kGy irradiation dose supported the Pt catalyst (Pt-Ti-P-300) and presented the optimal catalytic performance for DEMP and DMP degradation. Characterization results confirmed that OVs were successfully introduced to the catalysts. Meanwhile, OVs induced by electron beam irradiation expanded the light absorption range and improved the generation and separation of photogenerated carriers, which significantly enhanced the catalytic activity of the catalysts for PAE degradation. Importantly, the degradation mechanism and pathway of DMP were further explored by using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and gas chromatography–mass spectrometry (GC-MS). These findings provide important insights into the electron beam irradiation-mediated regulation of catalysts and the photothermal catalytic removal of PAEs in indoor environments.

The synthesis of high-performance catalysts for volatile organic compounds (VOCs) degradation under humid conditions is essential for their practical industrial application. Herein, a codoping strategy was adopted to synthesize the N-Co3O4-C catalyst with N, C codoping for low-temperature ethyl acetate (EA) degradation under humid conditions. Results showed that N-Co3O4-C exhibited great catalytic activity (T 90 = 177 °C) and water resistance (5.0 vol% H2O, T 90 = 178 °C) for EA degradation. Characterization results suggested that the C, N codoping weakened the Co-O bond strength, increased surface Co3+ and Oads species, and improved the low-temperature redox ability and the mobility of lattice oxygen species, which boosted the catalytic performance of N-Co3O4-C for EA degradation. Meanwhile, the N-doping-induced oxygen vacancies could interact with water vapor to generate extra active oxygen species, which enhanced the water resistance. Importantly, based on a series of characterization technologies, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and theoretical calculations, the synergistic effect of C, N codoping was systematically investigated and elucidated. The C doping induced the increase of surface area and the weakening of Co-O bond strength, which improved EA adsorption and lattice oxygen species activation to dissociate and oxidize EA, forming the key intermediate, acetate acid. N doping enhanced the adsorption and activation of gaseous oxygen species to form active oxygen species, attacking and breaking the C-C bond in acetate acid to accelerate EA deep oxidation, which synergistically facilitated EA degradation.

Defect engineering improves catalytic activity, electron transport efficiency, and stability by introducing defects such as oxygen vacancies, offering significant potential for applications in environmental remediation and energy conversion. Electron beam (EB) irradiation has emerged as a key technique in defect engineering, renowned for its mild reaction conditions and precise defect construction capabilities. This study synthesized defect-rich commercial TiO2 catalysts (P25) using high-energy EB irradiation to investigate the photodegradation efficiency of multicomponent VOCs. The EB irradiation technique promoted the formation of oxygen vacancies, which played a key role in the adsorption and activation of pollutant molecules. DFT calculations further confirmed the superior photocatalytic activity of the irradiated P25 catalyst. The photodegradation experiments showed that the 300P25 degraded pure ethyl acetate up to 99.05 % (40 min) and acetone up to 97.14 % (60 min), but toluene only up to 7.34 % (60 min). Interestingly, in acetone and toluene mixture, 300P25 achieved toluene removal as high as 68 % (60 min) with a rate constant (k) of 0.0181 min(-1), a 12.1-fold than pure toluene (0.0015 min(-1)). In-situ infrared spectroscopy analysis revealed that during the simultaneous degradation of toluene and acetone, acetone significantly promoted the deep oxidation of toluene, leading to the rapid oxidation of intermediate products (benzyl alcohol and benzaldehyde) to benzoic acid and smaller molecules. This work provides important guidance for developing efficient and stable photocatalysts for degrading multicomponent VOCs.

Herein, MnCo spinel catalysts with large surface area were successfully prepared by using Mn/Co-MOFs as precursors for toluene catalytic degradation.

The catalytic oxidation technology has been extensively employed for the control of air pollution caused by the large emissions of volatile organic compounds (VOCs). However, compared with the widespread research on single-component VOC elimination over supported Pd catalysts, the control of miscellaneous VOCs simultaneously and the revelation of their mutual influence still need to be solved eagerly. Herein, a mutual influence different from mutual inhibition or mutual promotion was revealed during the typical VOC mixture (toluene and acetone) degradation over metal-organic frameworks-derived Pd/ZrO2 catalysts by a series of experiments and characterizations. The results showed that an antagonism effect was observed between toluene and acetone during their mixture degradation; namely, acetone suppressed toluene oxidation, whereas toluene did not inhibit acetone degradation but promoted its degradation weakly. The mechanism was proposed in which the competitive adsorption inhibited the occurrence of acetone adsorption polymerization reaction to form mesityl oxide (MSO) at low temperatures, which induced the release of surface-active sites to enhance acetone oxidation. However, the polarity of acetone molecules induced its strong adsorption on the catalyst surface, which greatly suppressed toluene adsorption and the ring-opening reaction to generate maleic anhydride, weakening its degradation. This work provides guidance for supported Pd catalyst design for multicomponent VOC elimination.

The construction of metal-organic frameworks (MOFs) with highly efficient capture for volatile organic compounds (VOCs) adsorption under humid conditions is a significant yet formidable task. Herein, series of fluorinated UiO-67 modified with trifluoroacetic acid (TFA) and 4-fluorobenzoic acid were successfully synthesized for VOCs adsorption under high humidity conditions. Experiments results showed that UiO-67 modified with 4-fluorobenzoic acid (67-F) presented excellent adsorption capacity of 345 mg/g for toluene adsorption and exhibited great water resistance (10.0 vol% H2O, 374 mg/g toluene adsorption capacity). Characterization results indicated that the introduction of 4-fluorobenzoic acid induced the competitive coordination between 4-fluorobenzoic acid and 4,4-biphenyl dicarboxylic acid (BPDC) with Zr4+, causing the formation of abundant defects to provide extra adsorption sites. Meanwhile, the benzene ring in 4-fluorobenzoic acid enhanced the 7C-7C conjugation, causing the further promotion of VOCs adsorption capacity. More importantly, the water resistance mechanism was investigated and elucidated that the introduction of F decreased the surface energy of 67-F and its affinity with water. Meanwhile, the metal complex induced by the fluorinated modification produced an electron -dense pore environment, which greatly improved its chemical and water stability. This work provided a strategy for preparing an adsorbent with high water resistance for real -world VOCs adsorption at high humidity conditions.

In recent years, multifarious new materials have been developed for environmental governance. Thereinto, metal organic framework (MOF)-based catalysts have been widely employed for heterogeneous catalysis because of their high porosity to confine noble metal particles faraway from aggregation. However, the potential reactions between residual species from the material synthesis process and target pollutants, which could form highly toxic byproducts, are often neglected. Herein, we took the widely used Zr-MOF, UiO-66, with highly thermal stability supported Pd catalysts as the example to investigate how the residual species in catalysts are involved in aromatic volatile organic compounds (VOCs) degradation reaction. The results showed that residual Cl species originated from the ZrCl4 metal precursor participated in the VOC degradation reaction, leading to the production of various chlorine-containing byproducts, even the hypertoxicity dioxin precursor, dichlorobenzene. Meanwhile, the chlorination mechanism for the formation of chlorine-containing byproducts was revealed by density functional theory calculation. Furthermore, the highly efficient residual Cl removal approaches are proposed. Importantly, the migration and transformation of residual Cl during the degradation of five benzene series VOCs are comprehensively studied and elucidated. We anticipate that these findings will raise alarm about the neglected issue of residual species in MOF-based catalysts for heterogeneous catalysis, especially environmentally friendly catalysis.

Volatile organic compounds (VOCs) posed a significant threat to the sustainability of ecosystems and human health, and photocatalytic oxidation technology emerged as one of the promising strategies. In this work, Ndoped TiO2 composites were prepared by ball milling utilized melamine as a precursor for the photodegradation of high-concentration ethyl acetate under visible light. The electric field polarization effect of TiO2 facilitated the exposure of active sites, promoting separation and migration of photogenerated carriers. DFT calculations further demonstrated that N-TiO2 possessed better electron transition capabilities and stronger pollutant adsorption abilities. Notably, the optimized N-TiO2 (9-N-P25) exhibited an ethyl acetate removal rate of up to 98.8 % (2000 ppm) under visible light irradiation, and the speed constant k values (0.09488 min(-1)) was 2.66 folds higher than that of pure TiO2 (0.03571 min(-1)). The center dot O-2(-) and center dot OH free radicals played major roles in the photodegradation process, and the interaction mechanism between free radicals and pollutant molecules was analyzed through insitu infrared. Additionally, the mechanism of photocatalytic degradation of ethyl acetate by N-TiO2 was further elucidated. This work provided new insights into the semiconductor photodegradation of high-concentration VOCs, offering novel pathways for removing VOCs in the atmospheric environment.

Irradiation process can accelerate synthesis and induce various chemical reactions without the application of catalysts in organic framework materials. In recent years, more and more publications regarding the synthesis and modification of organic frameworks via different irradiation technologies indicates that irradiation process will play an important role in materials chemistry. This review presents an overview of the utilization of irradiation process to synthesize and modify the organic frameworks. Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), as the two most representative organic framework materials, have been widely applied in lots of fields because of their unique pore structure, physical and chemical properties. This review is meant to describe the effect of different irradiation on synthesis and modification of organic frameworks. Considering these particular aspects, the advantages of irradiation process compared with conventional heating method of synthesis and traditional material modification methods have been explained in detail. Finally, the wide application and future prospect of MOFs and COFs modified by irradiation in catalysis, adsorption, sensing, tumor therapy and energy with improved performance are elaborated. The application of irradiation technology provides a new strategy for material synthesis in industrial scale and the reference value for material modification in the future.

Graphene-based aerogels have attracted considerable interest in recent years for their ability to remove toxic pollutants, due to their attractive properties, which include a sufficient number of anchor positioning points, arbitrarily changing shapes, and adjustable functional groups and pore sizes. The potential methods for adsorption, degradation, and reduction of water and atmospheric pollutants using graphene-based aerogels have been thoroughly investigated. Firstly, this review introduced the current research on the application of graphene-based aerogels as environmentally efficient materials for removing water and atmospheric contaminants, including heavy metal ions, organic dyes, nitrogen oxides (NOx), and volatile organic compounds (VOCs). Secondly, the important role in promoting adsorption and catalysis and the types of modifications of graphene aerogels are discussed in depth. Finally, this review summarized the great potential of graphene-based aerogels as environmentally functional materials and put forward the challenges and prospects, aiming to promote the development and industrial application of graphene-based aerogels.

The design of efficient catalysts with great water-resistance for volatile organic compounds (VOCs) degradation is challenging. Herein, series of Mn-based catalysts with great catalytic activity were prepared via a novel non-thermal derivation by Na2CO3 solution treatment using Mn-MIL-100 as a sacrificial template. Among them, the Mn-Na-1.0 catalyst prepared by treating with 1.0 mol/L Na2CO3 solution presented the optimal toluene degradation performance (T-90 = 209 degrees C) and water-resistance (5.0 vol%). Characterization results suggested that the abundant surface Mn3+ and O-ads species, better surface lattice oxygen species mobility, low-temperature reducibility, and high surface area accounted for the great catalytic performance of the Mn-Na-1.0 catalyst. Importantly, the promotion of water vapor to toluene oxidation was observed and systematically elucidated by many characterizations and experiments. The results showed that the introduced water vapor was activated and dissociated to form dissociation adsorbed active oxygen species, which served as the additional active site and provided active oxygen species to accelerate the oxidation of intermediates and toluene mineralization. This work provided a novel approach for designing Mn-based catalysts with good water-resistance in VOCs degradation under actual industrial conditions.

In this paper, the effect of three monocarboxylic acids on MIL-125 synthesis was systematically investigated and the results were discussed in detail. X-ray diffractometry (XRD) and nitrogen adsorption-desorption curves indicated that small molecule acids (acetic acid, propionic acid and butyric acid) affected the morphology of MIL125 and induced lamellar pores and structural defects in the crystals. Thermogravimetric measurements confirmed the presence of acid-regulated defective metal-organic frameworks (MOFs). Electrochemical tests and density function theory calculations indicated that acid modulation could change the forbidden bandwidth of the material. The acid modification strategy effectively promoted the transfer of photogenerated electrons and enhanced the adsorption and activation of O2 and H2O molecules, generating reactive radicals. The modified MOFs also showed excellent performance in the removal of mixed toluene and chlorobenzene. The degradation pathways of the mixture were analyzed by in situ infrared (IR) and gas chromatography-mass spectrometry (GC-MS). The mixture was converted to chlorophenolic intermediates in the presence of reactive oxygen species, further decomposed to form ethers and ethanol, and finally formed small molecules such as carbon dioxide and water. A feasible method was provided for the preparation of photocatalysts for the treatment of mixed VOCs.

The regulation of metal-support interaction is one of the productive strategies to enhance volatile organic compounds (VOCs) deep degradation. Herein, Pd@ZrO2 catalysts were synthesized via using in-situ growth Zr-based metal organic framework (MOF) Pd@UiO-66 as the precursor to boost toluene deep degradation. Compared with Pd@ZrO2-Zr(OH)4 synthesized by using Zr(OH)4 as the precursor, MOF-derived Pd@ZrO2 catalysts with different calcination time exhibited more superior catalytic performance, water-resistance and stability. Characterizations results indicated the occurrence of interfacial interaction in MOF-derived Pd@ZrO2 induced the better reducibility at low-temperature and the generation of oxygen vacancies, enhanced Oads species content, weakened Zr-O bond strength, improved the mobility of Olat species, which caused its better toluene degradation performance. Simultaneously, in-situ diffuse reflectance infrared Fourier transform spec-troscopy results clarified that the interfacial interaction heightened the adsorption and activation ability for gaseous oxygen to form reactive oxygen species and replenish consumed Olat species, promoted toluene ring -opening reaction, reduced benzoate acid species cumulation, expedited the fast deeply degradation of toluene to CO2 and H2O. This work may provide a new perspective on MOF-derived catalysts with better performance for VOCs degradation deeply by tuning interfacial interaction.

The high specific surface area, adjustable porosity, and unique topological structure of metal–organic frameworks (MOFs) can be well inherited in their derivatives, which makes MOFs and their derivatives very promising in the elimination of typical gaseous pollutants by catalytic oxidation. In this paper, the synthesis methods of different types of MOFs and their derivative catalysts and their research progress in catalytic oxidation of typical gaseous pollutants are systematically reviewed. The effects of preparation methods, catalyst components, and experimental conditions on the performance of the catalyst were discussed, and the effects of the interaction between different metals on the performance of the catalyst were expounded. In addition, two important technical means of in situ experimental characterization and theoretical calculation to reveal the catalytic mechanism are introduced, and the reaction pathways and the reaction pathway and mechanism of pollutant degradation on some specific structures are summarized. Finally, the challenges and prospects of MOFs and their derivatives in catalytic applications are discussed.

Herein, a novel preparation method via non-thermal derivation by using Mn-MIL-100 as the precursor to synthesize MnOx catalysts was proposed. The synthesized catalysts were applied to toluene oxidation. Characterizations and experiments results showed that the more surface Mn3+, Oads species, large surface area, better low-temperature reducibility and higher lattice oxygen mobility of Mn-Na2CO3 prepared via Na2CO3 treatment induced its great catalytic activity for toluene oxidation.

The crystal engineering of metal oxide supports aims to enhance the performance of precious metal catalysts in semi-volatile organic compounds (SVOCs). Di (2-ethylhexyl) phthalate (DEHP) as one of the representative SVOCs in indoor environments, has become a research hotspot in recent years. For the catalytic oxidation of DEHP, Pt/TiO2 catalysts were prepared on supports of TiO2 with different crystalline phases (mixed phase (P25), anatase, and rutile). P25 exhibits a higher PtOx content due to its unique mixed crystalline phase, giving the best catalytic performance of the synthesized catalyst through light, thermal and photothermal catalytic experiments. The degradation of DEHP is optimized by a combination of photocatalysis and thermal catalysis. The intermediates and degradation pathways were analyzed through GC-MS and other characterization methods, and the possible degradation pathways were schematically studied. This work provides the possibility to rationalize the design of photothermal catalysts for SVOC removal.

The synthesis method of precious metal catalysts would affect the electronic metal-support interaction (EMSI) of catalysts, which further affected the catalytic activity. In this paper, Co3O4 was obtained as support by the pyrolysis of ZIF-67 as a template sacrificial agent, and Pt species were loaded by three different reduction methods. Among them, the catalyst produced by the NaBH4 reduction method possessed the best activity with T90 of 168 degrees C. Through a series of characterization and experiments, it was found that the EMSI of the catalyst was optimized by this synthesis method, which led to electron transfer among Pt species and Co3O4. The catalysts also exhibited excellent water resistance, stability, and recycling performance. The possible degradation mechanism of toluene was also revealed by in situ DRIFTS and GC-MS. This paper provided ideas for the construction of catalysts and a theoretical reference for the relevant verification of EMSI.

In the process of volatile organic compounds (VOCs) catalytic oxidation, the search of the reaction mechanism and the reaction rate-controlling part are the key and difficult elements of research. In this work, the intermediate products in the process of eliminating various VOCs by different catalytic technologies are systematically reviewed. Based on intermediates analysis, the advantages and disadvantages of various catalytic technologies in the control of by-products are described in detail. The paper also focuses on the detection techniques of characteristic intermediates in VOCs elimination, and discusses the characterization methods and their usage conditions. Finally, several factors are provided that affect the formation and conversion of intermediates. Especially, the effects of catalysts surface metal capacity and oxygen species on intermediates are discussed. It is believed that the review will provide a good basis and reference point for the exploration of VOCs catalytic oxidation pathways and the analysis of intermediate products.

Since the environmental hazards of volatile organic compounds (VOCs) are well known, heterogeneous catalysis has become one of the most popular methods to treat VOCs due to its environmental friendliness and simplicity of operation. Although a large number of reports have reviewed the application of catalytic oxidation for the degradation of VOCs, relatively few reports are based on this direction of metal organic frameworks (MOFs) and MOF derivatives. Herein, this paper reviews the recent applications of heterogeneous catalytic technologies in the degradation of VOCs, including photocatalysis, thermal catalysis and other catalytic approaches. The applications of MOFs and their derivatives in VOCs degradation, such as the progress of MOF-derived metal oxides in the treatment of toluene, were highlighted. The mechanisms of VOCs degradation by different catalytic approaches were systematically presented. Finally, we presented the views and directions of VOCs treatment technology development. We hope that this reaction type-oriented review will provide important insights into MOFs and MOF-derived materials for VOCs pollution control.