MOF-based Photocatalysts Research Articles

Designing S-scheme heterojunction via in situ converting partial NH2-MIL-68 into defective In2O3 for photocatalytic CO2 reduction

Intrinsic characteristics of metal–organic frameworks (MOFs) make them become promising candidates for the application of photocatalytic CO2 reduction. However, their photocatalytic activities are still unsatisfactory due to serious recombination of photogenerated charge carriers and insufficient light absorption. S-scheme heterojunction has demonstrated high superiority in the separation of charge carriers due to its unique structure and interface interaction. Nevertheless, it is difficult to construct it in MOF-based photocatalysts because of high interface connection requirements. Herein, a NH2-MIL-68 (In-MOF) is chosen as the research object. S-scheme heterojunction (In2O3@In-MOF) with oxygen vacancies (OVs) is easily constructed via in situ converting partial In-MOF into defective In2O3. The in-situ derivatization strategy is similar to epitaxial crystal growth, which could avoid drastic changes in the morphology of epitaxial growth rh-In2O3 to ensure the high-quality interface connection. The S-scheme heterojunction not only enhances the separation efficiency of photogenerated charge carriers of In-MOF, but also maintains the high reduction power of its photogenerated electrons as well as expanding its light absorption capacity. Therefore, In2O3@In-MOF exhibits enhanced photocatalytic CO2 reduction activity compared to those of pure In-MOF and In2O3. This work may open a potential pathway for the S-scheme heterojunction designing in the field of photocatalytic CO2 reduction.

Integration of polyoxometalate into defective UiO-66-NH2(Zr/Hf) for visible-light-driven hydrogen photogeneration

UiO-66 plays a crucial role in photocatalytic systems due to its superior stability and tunability. However, the charge transfer from organic ligands to metals is rarely involved in the photo-excitation of the pristine material. Herein, several Keggin-type Cs2.5H0.5PW12O40 (CsPW) were successfully incorporated into a bimetallic metal-organic framework (MOF) using a one-pot, one-step method, resulting in a series of defective CsPW@UNH(Hf-Zr) as optimized photocatalysts for visible-light-driven hydrogen evolution. Further investigations demonstrate that a Z heterojunction mechanism proceeds in the CsPW@UNH(0.65Hf) heterojunction to boost the charge separation via the chemical interaction between the CsPW and UNH(0.65Hf) components. The hydrogen evolution rate for 5 %CsPW@UNH(0.65Hf) is nearly two orders of magnitude greater than that of the bare UNH(Zr). The coexistence of Hf3+ and Zr3+ was observed in defective polyoxometalate-encapsulated MOF (POM@MOF) for the first time during photocatalysis, confirming the successful conjugated π electrons transition from the amine-containing ligand to bimetallic cluster. This study offers a novel guideline for exploring efficient MOF-based photocatalysts through defect engineering.

Defect engineering on metal-organic frameworks for enhanced photocatalytic reduction of Cr(VI)

Cr(VI) stands as a profoundly toxic chemical and photocatalysis technology has shown promising potential in photocatalytic reduction of Cr(VI) to Cr(III), where the reduced Cr(III) is less toxic and can be further precipitated in a wide pH range. Metal-organic frameworks (MOFs), as emerging class of porous coordination polymers, is expected to be ideal platform for photocatalysis. In this study, defect engineering on MOFs was applied to promote photoreduction of Cr(VI). The obtained oxygen vacancy-containing MIL-125-NH2 samples showed modified electron structure, adjusted surface and porous properties, and enriched active sites. Among these oxygen vacancy-containing MIL-125-NH2 samples, the 300-M (MIL-125-NH2 heated at 300 °C for 2 h under N2 atmosphere) displayed the most remarkable performance in terms of photocatalytic Cr(VI) reduction. The pronounced efficacy of 300-M is evident from the achieved removal rate of Cr (VI), reaching an impressive 98 % in just 20 mins (19.6 mgCr(VI) g−1cata min−1), in stark contrast to MIL-125-NH2, which exhibited a modest removal rate of 53 %. Remarkably, the k-value for 300-M is 5.1 times that of MIL-125-NH2, further underscoring the superior efficiency of 300-M. The photoreduction mechanism of 300-M was further substantiated through a battery of advanced characterization techniques including transient photocurrent, electrochemical impedance spectroscopy, fluorescence spectroscopy, the Mott-Schottky analysis, and electron spin resonance. Those results disclosed that oxygen vacancies and mesopores introduced via controlled heat treatment play a pivotal role in facilitating the photoreduction of Cr(VI) within the MIL-125-NH2 structure. More advanced characterizations for the structures of photocatalysts and the photocatalytic mechanisms including charge transfer path need further studied. The systematic exploration of temperature-dependent effects on material properties opens avenues for future research in designing efficient and versatile MOF-based photocatalysts for environmental remediation applications.

Ti4+ Ions-Doped Metal-Organic Framework (MOF-74) for Photoreduction of Carbon Dioxide.

The development of efficient and sustainable methods for reducing carbon dioxide (CO2) and converting it into valuable hydrocarbons has gained significant attention. In this study, researchers focused on Ti4+-doped metal-organic framework (MOF-74) photocatalysts. The incorporation of Ti4+ ions into the MOF-74 structure was achieved through a one-pot hydrothermal method. By replacing Zn2+ ions with Ti4+ ions in a substitutional manner, researchers have aimed to enhance the photocatalytic activity of the CO2 reduction. The obtained Ti4+-doped MOF-74 photocatalysts exhibited a significantly improved performance in the reduction of CO2 into carbon monoxide (CO). The doping of Ti4+ ions induced energy bands below the conduction band minimum (CBM) of MOF-74, extending the visible response range and enabling the photocatalysts to utilize a broader spectrum of light for catalytic reactions. This extension of the visible response range enables photocatalysts to utilize a broader spectrum of light for catalytic reactions. The incorporation of Ti4+ ions not only extends the visible response range but also suppresses charge carrier recombination. This work provides valuable insights into the design principles of MOF-based photocatalysts and paves the way for their practical implementation in addressing the energy crisis and reducing greenhouse gas emissions.

Construction of functionalized In-based metal organic framework/BiOCl1−xIx Z-scheme heterojunction for efficient photocatalytic degradation of tetracycline: Performance and mechanism

The environmental implications of antibiotics have drawn widespread attention. Numerous monomer-based bismuth oxide halide catalysts have been extensively studied to remove tetracycline (TC) from aquatic environments. Integrating bismuth oxide halide composites with In-based metal organic framework (NH2-MIL-68(In)) might potentially serve as a novel strategy. By meticulously adjusting Cl and I within the composite bismuth halide oxide (B-x), a suite of purpose built heterojunctions (NMB-x) were synthesized, which were engineered to facilitate the efficient photodegradation of TC in simulated and actual aquatic environments. The incorporation of Z-scheme heterojunctions yielded a significant enhancement in photocatalytic responsiveness and charge carrier separation. Notably, NMB-0.3 demonstrated remarkable TC removal efficiency of 88.52 ± 3.05%, which is 3.74 times of B-0.3 within 90 min. The apparent quantum yield was also increased from 8.97% (B-0.3) to 19.68% (NMB-0.3). The removal of TC from natural water bodies was also assessed. Moreover, the photocatalyst concentration, assessed using response surface method, was found to show influential factors on TC removal. In addition, density functional theory (DFT) simulations were employed to identify vulnerable sites within TC. Intermediates and pathways in the photodegradation of TC have also been inferred. Furthermore, a comprehensive environmental toxicity assessment of representative intermediates demonstrated that these intermediates exhibited significantly reduced environmental toxicity compared to TC. This study provides a new approach to the design strategy of efficient and environmentally friendly MOF-based photocatalysts.

Solar-driven production of highly concentrated hydrogen peroxide by Zn3In2S6/PCN-222 heterostructure

The key to storage of solar energy is to obtain highly concentrated hydrogen peroxide (H2O2). However, achieving the versatility of reaction, separation and collection in a one-step process is a great challenge. Herein, a Zn3In2S6/porphyrin-based porous coordination network (Zn3In2S6/PCN-222, abbreviated as ZIS/PCN) heterojunction with strong electron/energy transfer was prepared for H2O2 production and organic synthesis in a two-phase system. Interestingly, Zn3In2S6 regulated the hydrophilicity/hydrophobicity of PCN-222, enhanced oxygen adsorption and optimized the reaction system. Thus, hydrophobic ZIS/PCN photocatalysts were selectively dispersed in the organic phase, while the generated H2O2 existed in the aqueous phase, achiveing the spontaneous seperation and collection of H2O2. The results showed that the H2O2 production (302 mM) in ZIS/PCN systems was 1.7 and 107.7 times higher than that in PCN-222 and Zn3In2S6 systems, respectively, and 7.7 times higher than reported MOF-based photocatalysts in similar systems. This work widens the application of heterojunction engineering in H2O2 photoproduction.

Cu-Metalated Porphyrin-Based MOFs Coupled with Anatase as Photocatalysts for CO2 Reduction: The Effect of Metalation Proportion

Converting carbon dioxide (CO2) into valuable chemicals such as fossil resources via photocatalysis requires the development of advanced materials. Herein, we coupled zirconium-based metal–organic frameworks (MOFs) containing porphyrin and Cu-porphyrin with anatase TiO2. The effect of the porphyrin metalation proportion was also investigated. Notably, while the use of free-base porphyrin as the organic linker resulted in the development of PCN-224, the presence of Cu-porphyrin provided mixed-phase MOF structures containing both PCN-224 and PCN-222. MOF/TiO2 composites bearing partial (50%) metalated porphyrin were proven more active and selective towards the production of CH4, at ambient conditions, in the gas phase and using water vapors without the use of hole scavengers. The optimized composite bearing 15 wt.% of the partial metalated MOF was three times more active than pure TiO2 towards CH4 production. This study provides insights on the effect of precise materials engineering at a molecular level on the development of advanced MOF-based photocatalysts for CO2 reduction.

Construction of B doped g-C3N4/Ni-MOF-74 porous heterojunction with boosted carrier separation for photocatalytic H2 generation

Novel heterojunction is favored to improve the separation of photogenerated carriers and maintain high redox ability. A porous heterojunction combining porous metal-organic frameworks (MOF), Ni-MOF-74, and porous B-doped g-C3N4 (BCN) was fabricated for solar-light-driven H2 generation. The permeable surface and type-I carrier transfer mode not only created more reactive sites for H2 generation but also facilitated mass transfer at the contact interphase among BCN and Ni-MOF-74 due to a slight difference in their valence bond energy, which enhanced the excellent light trapping ability and expanded spectral absorbance range and thus solving the intrinsic drawback of fast charge recombination of pristine g-C3N4. Besides that, B-doping enhanced redox ability and transport separation, and the BCN/Ni-MOF-74 composite demonstrated dramatically reduced hydrogen production overpotential. The optimal BCN-NM-3 showed outstanding H2 generation up to 2190 μmol g−1h−1, almost 11 times higher than BCN. The current study will benefit the development of new MOF-based photocatalysts and be influential in meeting environmental demands in the future.

Manipulation of interfacial charge dynamics for metal-organic frameworks toward advanced photocatalytic applications.

Compared to other known materials, metal-organic frameworks (MOFs) have the highest surface area and the lowest densities; as a result, MOFs are advantageous in numerous technological applications, especially in the area of photocatalysis. Photocatalysis shows tantalizing potential to fulfill global energy demands, reduce greenhouse effects, and resolve environmental contamination problems. To exploit highly active photocatalysts, it is important to determine the fate of photoexcited charge carriers and identify the most decisive charge transfer pathway. Methods to modulate charge dynamics and manipulate carrier behaviors may pave a new avenue for the intelligent design of MOF-based photocatalysts for widespread applications. By summarizing the recent developments in the modulation of interfacial charge dynamics for MOF-based photocatalysts, this minireview can deliver inspiring insights to help researchers harness the merits of MOFs and create versatile photocatalytic systems.

RGO/MUT-15 nanocomposite as a Fenton-like photocatalyst for the degradation of Acid Yellow 73 under visible light.

The Fenton-like reaction is an advanced oxidation process (AOP) used to effectively eliminate organic pollutants. Fenton-like materials include metal-organic frameworks (MOFs) containing Fe, Co, Mn, and Cu metal ions. MOF-based photocatalysts with the highest performance can be designed and synthesized using these metal ions. A new Mn-based metal-organic framework with the formula of [Mn2(DClTPA)2(DMF)3] (MUT-15) containing 2,5-dichloroterephthalic acid (DClTPA) and N,N-dimethylformamide (DMF) was prepared via a solvothermal method. According to single-crystal X-ray analysis, MUT-15 (MUT = Materials from University of Tehran) has a tetragonal crystal system with the I41/a space group. A simple one-pot solvothermal method was used to prepare a rGO/MUT-15 nanocomposite. PXRD, FT-IR, TGA, FE-SEM, TEM, EDX, DRS, PL, EIS, and Mott-Schottky measurements were used to characterize the MUT-15 and rGO/MUT-15 nanocomposite. Under visible-light irradiation, MUT-15 and rGO/MUT-15 as Fenton-like photocatalysts degraded Acid Yellow 73 in only 10 min with outstanding photocatalytic activity rates of 92.39% and 96.10%, respectively. Thus, the Mn(II)-O clusters in MUT-15 significantly contributed to the degradation of Acid Yellow 73 through their Fenton-like effect.

Highly efficient photosynthesis of hydrogen peroxide by a stable Zr(IV)-based MOF with a diamino-functionalized ligand.

Metal-organic frameworks (MOFs) have emerged as a promising class of materials for solar-driven hydrogen peroxide (H2O2) generation due to their porosity, large surface area and designable molecular building blocks; however, producing H2O2 from oxygen and water without sacrificial agents remains a major challenge. Herein, we have constructed two UiO-67-type MOFs, UiO-67-NH2 and UiO-67-(NH2)2, by a solvothermal method using 2-amino-4,4'-biphenyldicarboxylic acid and 2,2'-diamino-4,4'-biphenyldicarboxylic acid as ligands, respectively. A variety of photochemical measurements have shown that the introduction of diamino groups into UiO-67-(NH2)2 not only enhances its absorption ability for visible light, but also facilitates the separation of photogenerated electron/hole pairs. Consequently, compared to monoamino-functionalized UiO-67-NH2, UiO-67-(NH2)2 exhibits a 5.5 times higher H2O2 production rate in pure water for 1 h. A two-step one-electron oxygen reduction reaction pathway for photocatalytic H2O2 production was suggested based on a series of control experiments and active species trapping tests by electron paramagnetic resonance spectra. This work provides new insights into the regulation of functionalized MOF ligands at the molecular level and a catalytic mechanism towards MOF-based photocatalysts for H2O2 production with high activity.

Dual metal centers within a water-stable Co/Ni bimetallic metal-triazolate framework contribute to durable photocatalysis for water treatment.

Bimetallic metal-organic frameworks (MOFs) have been studied extensively in various fields, including photocatalytic and electrocatalytic applications. The enhanced catalytic activity is typically attributed to the synergistic effect of the two metals, often without further explanation. Here, we demonstrate a CoNi-bimetallic triazolate MOF with fixed metal occupancy within the MOF's secondary building unit. Due to the difference in electronegativity and so on, the charge redistribution between the two metal centers could be responsible for the enhanced photocatalytic activity. In addition, the metal(II)-triazolate MOFs we synthesized exhibit unique metal-N coordination and a strong bond between the metal center and triazole ring. Therefore, their crystal structure and high porosity are highly retained even after exposure to humid environments for several months or stirring in water for several days. Overall, the CoNi-bimetallic triazolate MOF combines the excellent water stability and high surface area of its two monometallic counterparts. It can be further tailored to yield the highest colloidal stability during photocatalytic water treatment. As a result, the dual metal centers within the bimetallic MOF, combined with boosted colloidal stability, demonstrate the highest reactive oxygen species generation and promising antibacterial performance compared to their Ni- or Co-based counterparts. These findings shed light on the future design of robust MOF-based photocatalysts, particularly bimetallic ones.

Metal-organic framework-based S-scheme heterojunction photocatalysts.

Photocatalysis is a promising technology to resolve energy and environmental issues, where the design of high-efficiency photocatalysts is the central task. As an emerging family of photocatalysts, semiconducting metal-organic frameworks (MOFs) with remarkable features have demonstrated great potential in various photocatalytic fields. Compared to MOF-based photocatalysts with a single component, construction of S-scheme heterojunctions can render MOFs with enhanced charge separation, redox capacity and solar energy utilization, and thus improved photocatalytic performance. Herein, an overview of the recent advances in the design of MOF-based S-scheme heterojunctions for photocatalytic applications is provided. The basic principle of S-scheme heterojunctions is introduced. Then, three types of MOF-based S-scheme heterojunctions with different compositions are systematically summarized including MOF/non-MOF, MOF-on-MOF and MOF-derived heterojunctions. Afterwards, the enhanced performances of MOF-based S-scheme heterojunctions in hydrogen production, CO2 reduction, C-H functionalization, H2O2 production and wastewater treatment are highlighted. Lastly, the current challenges and future prospects regarding the design and applications of MOF-based S-scheme heterojunctions are discussed to inspire the further development of this emerging field.

Ligand Defect-Induced Active Sites in Ni-MOF-74 for Efficient Photocatalytic CO2 Reduction to CO.

The conversion of CO2 into valuable carbon-based products using clean and renewable solar energy has been a significant challenge in photocatalysis. It is of paramount importance to develop efficient photocatalysts for the catalytic conversion of CO2 using visible light. In this study, the Ni-MOF-74 material is successfully modified to achieve a highly porous structure (Ni-74-Am) through temperature and solvent modulation. Compared to the original Ni-MOF-74, Ni-74-Am contains more unsaturated Ni active sites resulting from defects, thereby enhancing the performance of CO2 photocatalytic conversion. Remarkably, Ni-74-Am exhibits outstanding photocatalytic performance, with a CO generation rate of 1380 µmol g-1 h-1 and 94% CO selectivity under visible light, significantly surpassing the majority of MOF-based photocatalysts reported to date. Furthermore, experimental characterizations reveal that Ni-74-Am has significantly higher efficiency of photogenerated electron-hole separation and faster carrier migration rate for photocatalytic CO2 reduction. This work enriches the design and application of defective MOFs and provides new insights into the design of MOF-based photocatalysts for renewable energy and environmental sustainability. The findings of this study hold significant promise for developing efficient photocatalysts for CO2 reduction under visible-light conditions.

Multilevel-Regulated Metal-Organic Framework Platform Integrating Pore Space Partition and Open-Metal Sites for Enhanced CO2 Photoreduction to CO with Nearly 100% Selectivity.

Rational design and regulation of atomically precise photocatalysts are essential for constructing efficient photocatalytic systems tunable at both the atomic and molecular levels. Herein, we propose a platform-based strategy capable of integrating both pore space partition (PSP) and open-metal sites (OMSs) as foundational features for constructing high-performance photocatalysts. We demonstrate the first structural prototype obtained from this strategy: pore-partitioned NiTCPE-pstp (TCPE = 1,1,2,2-tetra(4-carboxylphenyl)ethylene, pstp = partitioned stp topology). Nonpartitioned NiTCPE-stp is constructed from six-connected [Ni3(μ3-OH)(COO)6] trimer and TCPE linker to form 1D hexagonal channels with six coplanar OMSs directed at channel centers. After introducing triangular pore-partitioning ligands, half of the OMSs were retained, while the other half were used for PSP, leading to unprecedented microenvironment regulation of the pore structure. The resulting material integrates multiple advanced properties, including robustness, wider absorption range, enhanced electronic conductivity, and high CO2 adsorption, all of which are highly desirable for photocatalytic applications. Remarkably, NiTCPE-pstp exhibits excellent CO2 photoreduction activity with a high CO generation rate of 3353.6 μmol g-1 h-1 and nearly 100% selectivity. Theoretical and experimental studies show that the introduction of partitioning ligands not only optimizes the electronic structure to promote the separation and transfer of photogenerated carriers but also reduces the energy barrier for the formation of *COOH intermediates while promoting CO2 activation and CO desorption. This work is believed to be the first example to integrate PSP strategies and OMSs within metal-organic framework (MOF) photocatalysts, which provides new insight as well as new structural prototype for the design and performance optimization of MOF-based photocatalysts.

Synergistic effect on photocatalytic CO2 reduction of facet-engineered Fe-soc-MOFs with photo-deposited PtO species

Photocatalytic CO2 reduction reaction (PCO2RR) holds potential for mitigating global warming and achieving carbon neutrality. Metal-organic frameworks (MOFs) have emerged as promising photocatalysts due to their tunable light absorption, CO2 adsorption and photoelectrical properties. This study reports synergistic effect of facet engineering and photo-deposited PtO species on Fe-soc-MOFs for enhanced PCO2RR performance. Three Fe-soc-MOFs, namely Fe-soc-O, Fe-soc-M and Fe-soc-C, were synthesized and evaluated the photocatalytic properties in a gas–solid phase system using H2O as sacrificial agent. Fe-soc-O exposing eight {111} facets exhibits the highest photocatalytic activity, achieving a CO selectivity of 63.4 %. After depositing PtO species, Fe-soc-O1.5 (1.5 represents 1.5 wt% Pt loading) demonstrates the most pronounced improvement in performance, with CO and CH4 yields of 285.6 and 18.1 µmol/g, surpassing Fe-soc-O by ratio of 11.8 and 1.2, respectively. Notably, Fe-soc-O1.5 shows an impressive CO selectivity of 94.0 %. The enhanced CO2-to-CO conversion was attributed to the efficient separation and transfer of photo-induced electrons, along with effective adsorption/desorption of intermediates on the photocatalyst surface. This work underscores the significance of integrating facet engineering and PtO deposition to optimize MOF-based photocatalysts for efficient CO2 reduction. The findings provide valuable insights for design of high-performance catalysts toward sustainable CO2 utilization.

Encapsulation of carbon-nanodots into metal-organic frameworks for boosting photocatalytic upcycling of polyvinyl chloride plastic

Although polyvinyl chloride (PVC) ranks as the third most mass-produced synthetic plastic, the chemical upcycling of non-biodegradable PVC waste remains a significant challenge. Herein, carbon nanodots combined with the metal-organic framework (CDs/Zr-MOF) are fabricated for photocatalytic upcycling of PVC. Specifically, the ultra-small-sized CDs (∼2.0 nm) are encapsulated into Zr-MOF pores via a mild pyrolysis strategy. The maintained MOF structure facilitates charge/mass transfer and improves the surface-to-volume ratio of active sites of CDs. The CDs/Zr-MOF exhibits high activity for PVC conversion of ∼76.5% towards acetic acid with a yield of ∼14%. The mechanism investigation indicates the generated •OH radicals can efficiently trigger cleavage of C-Cl/C-C bonds of PVC. Moreover, the reduction of the energy barrier for the hydroxylation reaction as a rate-limiting step contributed to improved PVC conversion performance. This work offers a feasible method for fabricating nanoparticle-embedded MOF-based photocatalysts and provides new insights into the chemical upcycling of plastics.

Recent Advances in Metal-Organic Framework (MOF)-Based Photocatalysts: Design Strategies and Applications in Heavy Metal Control.

The heavy metal contamination of water systems has become a major environmental concern worldwide. Photocatalysis using metal-organic frameworks (MOFs) has emerged as a promising approach for heavy metal remediation, owing to the ability of MOFs to fully degrade contaminants through redox reactions that are driven by photogenerated charge carriers. This review provides a comprehensive analysis of recent developments in MOF-based photocatalysts for removing and decontaminating heavy metals from water. The tunable nature of MOFs allows the rational design of composition and features to enhance light harvesting, charge separation, pollutant absorptivity, and photocatalytic activities. Key strategies employed include metal coordination tuning, organic ligand functionalization, heteroatom doping, plasmonic nanoparticle incorporation, defect engineering, and morphology control. The mechanisms involved in the interactions between MOF photocatalysts and heavy metal contaminants are discussed, including light absorption, charge carrier separation, metal ion adsorption, and photocatalytic redox reactions. The review highlights diverse applications of MOF photocatalysts in treating heavy metals such as lead, mercury, chromium, cadmium, silver, arsenic, nickel, etc. in water remediation. Kinetic modeling provides vital insights into the complex interplay between coupled processes such as adsorption and photocatalytic degradation that influence treatment efficiency. Life cycle assessment (LCA) is also crucial for evaluating the sustainability of MOF-based technologies. By elucidating the latest advances, current challenges, and future opportunities, this review provides insights into the potential of MOF-based photocatalysts as a sustainable technology for addressing the critical issue of heavy metal pollution in water systems. Ongoing efforts are needed to address the issues of stability, recyclability, scalable synthesis, and practical reactor engineering.

High performance photocatalyst TiO2@UiO-66 applied to degradation of methyl orange

MOFs have considerable adsorption capacity due to their huge specific surface area. They have the characteristics of photocatalysts for their organic ligands can absorb photons and produce electrons. In this paper, the photodegradation properties of TiO2 composites loaded with UiO-66 were investigated for the first time for MO. A series of TiO2@UiO-66 composites with different contents of TiO2 were prepared by a solvothermal method. The photocatalytic degradation of methyl orange (MO) was performed using a high-pressure mercury lamp as the UV light source. The effects of TiO2 loading, catalyst dosage, pH value, and MO concentration were investigated. The results showed that the degradation of MO by TiO2@UiO-66 could reach 97.59% with the addition of only a small amount of TiO2 (5 wt%). TiO2@UiO-66 exhibited significantly enhanced photoelectron transfer capability and inhibited efficient electron–hole recombination compared to pure TiO2 in MO degradation. The composite catalyst indicated good stability and reusability when they were recycled three times, and the photocatalytic reaction efficiencies were 92.54%, 88.76%, and 86.90%. The results provide a new option to design stable, high-efficiency MOF-based photocatalysts.

MOF-Based Photocatalytic Membrane for Water Purification: A Review.

Photocatalytic membranes can effectively integrate membrane separation and photocatalytic degradation processes to provide an eco-friendly solution for efficient water purification. It is of great significance to develop highly efficient photocatalytic membranes driven by visible light to ensure the long-term stability of membrane separation systems and the maximum utilization of solar energy. Metal-organic framework (MOF) is an emerging photocatalyst with a well-defined structure and tunable chemical properties, showing a broad application prospect in the construction of high-performance photocatalytic membranes. Herein, this work provides a comprehensive review of recent advancements in MOF-based photocatalytic membranes. Initially, this work outlines the main tailoring strategies that facilitate the enhancement of the photocatalytic activity of MOF-based photocatalysts. Next, this work introduces commonly used methods for fabricating MOF-based photocatalytic membranes. Subsequently, this work discusses the application and mechanisms of MOF-based photocatalytic membranes toward organic pollutant degradation, metal ion removal, and membrane fouling mitigation. Finally, challenges in developing MOF-based photocatalytic membranes and their practical applications are presented, while also pointing out future research directions toward overcoming these existing limitations.