Metal-organic Frameworks Structures Research Articles

An insight Into Surface and Diffusion Characteristics of UiO‐66@ZIF‐8 Core–Shell MOF for Asymmetric Supercapacitors with Unprecedented Energy Density

AbstractIn this study, nanosized zeolitic imidazolate framework‐8 (ZIF‐8) crystal has been produced on the universitetet i oslo‐66 (UiO‐66) metal–organic framework (MOF) to make core–shell structure using a layer‐by‐layer deposition method. In comparison to the pristine UiO‐66 and ZIF‐8, the core–shell MOF exhibits superior performance in terms of specific capacitance. This enhanced performance is attributed to its remarkable ability to facilitate the rapid diffusion of electrolyte ions through nanosized ZIF‐8 and enhance the electron transfer process involving the inner and outer metal ions within the UiO‐66@ZIF‐8 structure. Remarkably, the core–shell structure achieves an impressive specific capacitance of 588.8 F g−1 at a current density of 0.5 A g−1 using 1 m sulfuric acid (H2SO4) aqueous electrolyte. Additionally, the UiO‐66@ZIF‐8 core–shell material is demonstrated as a positive electrode, coupled with activated carbon (AC) derived from waste tissue paper serving as the negative electrode, in the fabrication of an asymmetric supercapacitor (ASC) device. At a power density of 400 W kg−1, this assembled asymmetric device delivers a notably high energy density of 53 Wh kg−1 along with a cyclic stability of 94.8% after 10 000 cycles. This study substantiates the superior performance of the UiO‐66@ZIF‐8 core–shell MOF structure as a highly effective supercapacitor electrode material, surpassing the performance of its pristine MOF counterparts.

Methotrexate-loaded Fe-metal organic frameworks: Synthesis, characterizations, and drug release investigations

Efficient diagnoses and effective treatment of diseases like cancer can be achieved by designing and developing targeted and controlled drug delivery systems. Metal-organic frameworks (MOFs) are promising drug delivery systems due to large surface area, tunable pore sizes, and controlled drug release. Herein, we report the loading and release of methotrexate (MTX) in MIL-101-Fe MOF as a drug delivery system. The functional groups, crystal structure, and morphology of the as-synthesized MOF was determined by Fourier transform infrared spectroscopy (FTIR), powdered X-ray diffraction and scanning electron microscopy (SEM), respectively. Interestingly, the MOF exhibited 84 % encapsulation efficiency for MTX and 62 % release in the initial 50 h at pH 5.5, which is ideal for tumor tissue. The MTX@MIL-101-Fe effectively killed the HeLa cells from human cervical cancer. Particularly noteworthy was that neither MIL-101-Fe nor MTX@MIL-101-Fe showed toxicity to healthy Vero cells. It proves that the Methotrexate was released from MTX@MIL-101-Fe in cancer cells at pH 5.5 and caused apoptosis. Theoretical studies used density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to explore three possible Methotrexate-MIL-101-Fe encapsulation complexes. The complex with the drug attached at the carboxylate-bridge site showed the highest binding. Moreover, a decrease in the calculated band gap was also observed during the encapsulation process. This study suggests that MIL-101-Fe can be a promising candidate for target-specific and efficient delivery of Methotrexate to cancer cells with reduced side effects.

Mechanistical Insights into the Ultrasensitive Detection of Radioactive and Chemotoxic UO22+ Ions by a Porous Anionic Co-Metal-Organic Framework.

Development of a simple, cost-efficient, and portable UO22+ sensory probe with high selectivity and sensitivity is highly desirable in the context of monitoring radioactive contaminants. Herein, we report a luminescent Co-based metal-organic framework (MOF), {[Me2NH2]0.5[Co(DATRz)0.5(NH2BDC)]·xG}n (1), equipped with abundant amino functionalities for the selective detection of uranyl cations. The ionic structure consists of two types of channels decorated with plentiful Lewis basic amino moieties, which trigger a stronger acid-base interaction with the diffused cationic units and thus can selectively quench the fluorescence intensity in the presence of other interfering ions. Furthermore, the limit of detection for selective UO22+ sensing was achieved to be as low as 0.13 μM (30.94 ppb) with rapid responsiveness and multiple recyclabilities, demonstrating its excellent efficacy. Density functional theory (DFT) calculations further unraveled the preferred binding sites of the UO22+ ions in the tubular channel of the MOF structure. Orbital hybridization between NH2BDC/DATRz and UO22+ together with its significantly large electron-accepting ability is identified as responsible for the luminescence quenching. More importantly, the prepared 1@PVDF {poly(vinylidene difluoride)} mixed-matrix membrane (MMM) displayed good fluorescence activity comparable to 1, which is of great significance for their practical employment as MOF-based luminosensors in real-world sensing application.

Metal-Organic Framework Nanomaterials as a Medicine for Catalytic Tumor Therapy: Recent Advances.

Nanomaterials, with unique physical, chemical, and biocompatible properties, have attracted significant attention as an emerging active platform in cancer diagnosis and treatment. Amongst them, metal-organic framework (MOF) nanostructures are particularly promising as a nanomedicine due to their exceptional surface functionalities, adsorption properties, and organo-inorganic hybrid characteristics. Furthermore, when bioactive substances are integrated into the structure of MOFs, these materials can be used as anti-tumor agents with superior performance compared to traditional nanomaterials. In this review, we highlight the most recent advances in MOFs-based materials for tumor therapy, including their application in cancer treatment and the underlying mechanisms.

Tune and turn the pyrolysis of metal organic frameworks towards stable supported nickel catalysts for the dry reforming of methane

Dry reforming of methane (DRM) is an inimitable approach for eliminating both greenhouse gases, methane and CO2, while producing synthesis gas which further can be converted to added-value fuels. However, the industrialization of DRM has been limited due to sintering and coking to the catalysts under the harsh reaction conditions. Here, we propose a new methodology for producing tunable supported nickel-based catalysts for DRM using metal organic frameworks (MOFs) as precursors of the catalyst components. In particular, Ni- and La-MOFs were coalesced using sonication and then calcined at different temperatures to produce catalysts with tailored Ni metal size (5–20 nm) and tuned strong metal-support interactions (SMSI). Here, the synthesis of nickel and nickel oxide nanoparticles embedded on lanthanum-based supports by controlled calcination of the MOF structures is demonstrated; the Ni supported catalysts were then used for DRM reaction. Among the developed catalysts, the catalyst produced following calcination at 500 °C (Ni-La-500) has shown stable and high CH4 conversion rates under DRM conditions at 800 °C with negligible carbon formation at elevated gas hourly space velocities. Further, the catalytic performance of Ni-La-500 catalyst (sonicated) was compared to the physically mixed MOFs derived catalyst (Ni-La-500-PM), conventional wetness impregnated catalyst (Ni-La-500 WI), Ni-MOF derived unsupported catalyst (Ni-500), and lower Ni concentration catalyst (sonicated, 10Ni-La-500). The observed CH4 conversion rates at 50,000 mL·gcat–1·h−1 GHSV are 81.8, 67.9, 85.4, 34.7, and 57.9 % for Ni-La-500, Ni-La-500 PM, Ni-La-500 WI, Ni-500, and 10Ni-La-500 catalysts, respectively after 24 h of DRM reaction. With isotopic studies, it was found that the 18O exchange rate was higher in case of Ni-La-500-PM catalyst (8.1 mmol·g−1) as compared to Ni-La-500 catalyst (5.5 mmol·g−1). Prior interaction between MOFs, calcination temperatures, reaction conditions, and the carbon pathways during catalytic activity dictates the conversion rates and selectivity of the products. Overall, with the herein proposed approach of MOF-derived supported catalysts exceptional conversion rates and stability during the DRM reaction with nominal coking and sintering were demonstrated, solving the two major challenges faced by conventional and unsupported catalysts.

Supported Ni nanoparticles derived from MOFs as a highly active catalyst for benzene hydrogenation

Metal-organic frameworks (MOFs) is easy to agglomerate at high temperature, resulting in the rapid collapse of the MOFs structure and the aggregation of metal sites. In this paper, Al2O3 is used as the support material to support the in-situ synthesis of Ni-MOF on the surface, and the metal Ni nanoparticles are successfully fixed on the Al2O3. The results showed that both Ni/Ni-MOF-300 and Ni/NA-MOF-300 catalysts reduced at 300 ℃ have good hydrogenation activity of benzene, and Ni/Ni-MOF-450 catalysts reduced at 450 ℃ formed huge Ni aggregates, which significantly reduced the hydrogenation activity of benzene. However, Ni/NA-MOF-450 catalyst reduced at 450 ℃ can effectively resist the metal Ni agglomeration caused by the collapse of MOFs structure at high temperature, and has better hydrogenation activity of benzene.

Multivariate mesoporous MOFs with regulatable hydrophilic/hydrophobic surfaces as a versatile platform for enzyme immobilization

Zeolitic imidazole frameworks materials-8 (ZIF-8), a member of the metal-organic framework (MOFs) series, have been extensively used as a host matrix for enzyme immobilization. However, the microporous structure and hydrophobicity, as well as the protonation of the precursor 2-methylimidazole (2-MeIm) of ZIF-8, remain considerable challenges in maintaining the activity of immobilized enzymes. Here, novel multivariate mesoporous MOFs (mMOFs) with regulatable hydrophilic/hydrophobic surfaces were designed by the multivariate competitive strategy and pore modification engineering. 3-Methyl-1H-1,2,4-triazole (3-MTZ) and 5-methyltetrazole (5-MTA) were employed to partially replace 2-MeIm. These were then combined with zinc sulfate heptahydrate (soft templates) to yield mMOFs in a methanol solution. As a proof-of-concept application, we used mMOFs as carriers for enzyme immobilization and investigated the properties of the immobilized enzymes. Benefiting from their mesoporous structure, hydrophilic surface, and improved microenvironment, multivariate mMOFs exhibit a strong ability to stabilize enzyme conformation and increase enzyme activity compared with traditional ZIF-8. Our study offers an avenue for the controllable preparation of well-designed MOF structures, which will further broaden the application opportunities of MOF materials for enzyme immobilization.

Supramolecular Structure of the β-Cyclodextrin Metal-Organic Framework Optimizes Iodine Stability and Its Co-delivery with l-Menthol for Antibacterial Applications.

The spread of upper respiratory tract (URT) infections harms people's health and causes social burdens. Developing targeted treatment strategies for URT infections that exhibit good biocompatibility, stability, and strong antimicrobial effects remains challenging. The dual antimicrobial and antiviral effects of iodine (I2) in combination with the cooling sensation of l-menthol in the respiratory tract can simultaneously alleviate URT inflammation symptoms. However, as both I2 and l-menthol are volatile, addressing stability issues is crucial. In this study, a potassium iodide β-cyclodextrin metal-organic framework [β-CD-POF(I)] with appropriate particle size was used to coload and deliver I2 and l-menthol. Primarily, β-CD-POF(I) was employed as the most efficient carrier to significantly enhance the stability of I2, surpassing any other known protection strategies in the pharmaceutical field (CD complexations, PVP conjugations, and cadexomer iodine). The mechanism underlying the improvement in stability of I2 by β-CD-POF(I) was investigated through scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and molecular docking. The results revealed that the key processes involved in improving stability were the inclusion of I2 by β-CD cavities in β-CD-POF(I) and the formation of polyiodide anion between iodine ions and I2. Furthermore, the potential of β-CD-POF(I) to load and deliver drugs was validated, and coloading of l-menthol and I2 demonstrated reliable stability. β-CD-POF(I) achieved a rate of URT deposition ≥95% in vitro, and the combined antibacterial effects of coloaded I2 and l-menthol was better than I2 or PVP-I alone, with no irritation noted following URT administration in rabbits. Therefore, the stable coloading of drugs by β-CD-POF(I), leading to enhanced antimicrobial effects, provides a new strategy for treating URT infections.

Synthesis of the composites of carbon quantum dots and metal organic framework and their application in hydrogen evolution

The Ti-MIL-125 metal-organic framework (MOF) functions as a nanoreactor, producing carbon quantum dots (CQDs) within its structure and forming CQD/MOF composites. Similarly, a Pt-CQD/MOF three-component composite is synthesized. Their properties, along with those of CQDs and MOF-free-CQDs (mf-CQDs) enclosed within the MOF, undergo assessment and comparison. Integrating CQDs and Pt minimally alters the MOF structure but reduces specific surface areas due to incorporation. The emitted wavelength of CQD/MOF (570 nm) differs from pristine CQDs (450 nm) and mf-CQDs (496 nm), indicating MOF influence on CQDs' growth and photoluminescence. HOMO and LUMO levels of CQDs/MOF, measured via ultraviolet photoelectron spectroscopy and low-energy inverse photoelectron spectroscopy, are more positive than those of the MOF, suggesting heterogeneous junction formation, aiding electron separation. CQD/MOF exhibits a modest photocatalytic hydrogen evolution rate of 20.4 μmol/g/h. Conversely, Pt-CQD/MOF significantly boosts the rate to 2213 μmol/g/h, underscoring Pt's pivotal catalytic role.

An overview of Metal–Organic Frameworks as potential platform: Sensing for detection environmental pollutants and drug delivery applications

Metal Organic Frameworks (MOFs) represent a novel class of materials, characterized by their ability to form extended porous crystalline structures through the linkage of inorganic clusters or metallic ions with organic ligands. The availability of broad range of metal centres and type of organic linkers gives us opportunity for tailoring physical and chemical properties of MOFs. These modified MOFs opens up new channels for the customization of new devices needed for specific purposes. Though MOFs have been explored for significant applications in different sectors such as gas storage, proton conduction, biotechnological, biomedical sciences, catalysis, and separation, but drug delivery and the sensing applications has been taken exclusively at the manuscript. So, this article entails an overview of various synthetic methodology of low dimensional MOFs such as 1D and 2-D MOFs, and also focuses on their applications in sensing and drug delivery. This stems from their remarkable catalytic chemistry and their compatibility with a broad spectrum of materials. Furthermore, the 2-D layered structure of MOFs and their distinctive coordination of metal ions with organic ligands have emerging interest in the recent years.

Bimetal-Organic Frameworks Incorporating Both Hard and Soft Base Active Sites for Heavy Metal Ion Capture.

The design and synthesis of stable porous materials capable of removing both hard and soft metal ions pose a significant challenge. In this study, a novel metal-organic framework (MOF) adsorbent named CdK-m-COTTTB was developed. This MOF material was constructed using sulfur-rich m-cyclooctatetrathiophene-tetrabenzoate (m-H4COTTTB) as the organic ligand and oxygen-rich bimetallic clusters as the inorganic nodes. The incorporation of both soft and hard base units within the MOF structure enables effective removal of various heavy metal ions, including both soft and hard acid species. In single-component experiments, the adsorption capacity of CdK-m-COTTTB for Pb2+, Tb3+, and Zr4+ ions reached levels of 636.94, 432.90, and 357.14 mg·g-1, respectively, which is comparable to specific MOF absorbents. The rapid adsorption process was found to be chemisorption. Furthermore, CdK-m-COTTTB exhibited the capability to remove at least 12 different metal ions in both separate and multicomponent solutions. The material demonstrated excellent acid-base stability and renewability, which are advantageous for practical applications. CdK-m-COTTTB represents the first reported pristine MOF material for the removal of both hard and soft acid metal ions. This work serves as inspiration for the design and synthesis of porous crystalline materials that can efficiently remove diverse heavy metal pollutants.

Probing ligand conformation and net dimensionality in a series of tetraphenylethene-based metal-organic frameworks.

Tetraphenylethene-based ligands with lowered symmetry are promising building blocks for the construction of novel luminescent metal-organic frameworks (MOFs). However, few examples have been reported, and predicting the ligand conformation and the dimensionality of the resulting MOF remains challenging. In order to uncover how synthetic conditions and accessible ligand conformations may affect the resulting MOF structure, four new MOF structures were synthesized under solvothermal conditions using the meta-coordinated tetraphenylethene-based ligand m-ETTC and paddlewheel SBUs composed of Co(II), Cu(II), and Zn(II). WSU-10 (WSU = Washington State University) is formed with either Zn or Cu comprising stacked psuedo-2D layers. The dimensionality of WSU-10 can be intentionally increased through the addition of pyrazine as a pillar ligand into the synthesis, forming the 3D structure WSU-11. The third structure, WSU-20, is formed by the combination of Zn or Co with m-ETTC and is intrinsically 3D without the use of a pillar ligand; interestingly, this is the result of a distortion in the paddlewheel SBU. Finally, Cu was also found to form a new structure (WSU-12), which displays an m-ETTC conformation unique from that found in the other isolated MOFs. Structural features are compared across the series and a mechanistic relationship between WSU-10 and -20 is proposed, providing insight into the factors that can encourage the generation of frameworks with increased dimensionality.

Synthesis and characterization of a β-cyclodextrin-MOF-based porous hydrogel for efficient adsorption of Au3+, Ag+, and Pb2+ ions

Wastewater containing heavy metal ions produced by electroplating, smelting and other industries poses a threat to human safety. Recently, metal–organic frameworks (MOFs) have emerged as porous crystalline adsorbents for the removal of heavy metal ions. Starch-derived cyclodextrins (CDs), a series of cyclic oligosaccharides, have been explored for fabrication of cost-efficient MOF materials. However, the coordination bonds in CD-based MOFs can be destroyed by water, which limits their application as absorbent materials for the removal of heavy metal ions from wastewater. In this work, a β-CD-MOF-based porous hydrogel was developed by incorporating a crosslinked hydrogel network based on acrylic acid (AA) and N,N’-methylenebis(acrylamide) (MBA) monomers into a β-CD-based MOF structure. The synthesized porous hydrogel, denoted A/M−CDMOF−gel, not only showed enhanced structural stability but also exhibited excellent properties for simultaneous adsorption of Au3+, Ag+, and Pb2+ ions. A kinetic study revealed that the A/M−CDMOF−gel had a satisfactory binding rate within 60 min of contact, and the higher fit coefficient from the pseudo-second-order model indicated its chemical adsorption property. Moreover, according to the Langmuir isotherm model fitting results, the maximum capacity of the A/M−CDMOF−gel reached 316.4, 60.9, and 414.2 mg/g for Au3+, Ag+, and Pb2+, respectively. Therefore, the regenerable A/M−CDMOF−gel adsorbent is expected to provide ideas for the development of renewable absorbent materials in the field of wastewater treatment and remediation.

Dehydration-Induced Cluster Consolidation in a Metal-Organic Framework for Sieving Hexane Isomers.

Metal-organic frameworks (MOFs) that exhibit dynamic phase-transition behavior under external stimuli could have great potential in adsorptive separations. Here we report on a zinc-based microporous MOF (JNU-80) and its reversible transformation between two crystalline phases: large pore (JNU-80-LP) and narrow pore (JNU-80-NP). Specifically, JNU-80-LP can undergo a dehydration-induced cluster consolidation under heat treatment, resulting in JNU-80-NP with a reduced channel that allows exclusion of di-branched hexane isomers while high adsorption of linear and mono-branched hexane isomers. We further demonstrate the fabrication of MOF-polymer composite (JNU-80-NP-block) and its application in the purification of di-branched isomers from liquid-phase hexane mixtures (98% di-branched) at room temperature, affording the di-branched hexane isomers with 99.5% purity and close to 90% recovery rate over ten cycles. This work illustrates an interesting dehydration-induced cluster consolidation in MOF structure and the ensuing channel shrinkage for sieving di-branched hexane isomers, which may have important implications for the development of MOFs with dynamic behavior and their potential applications in non-thermal driven separation technologies.

Improving gas adsorption modeling for MOFs by local calibration of Hubbard U parameters.

While computational screening with density functional theory (DFT) is frequently employed for the screening of metal-organic frameworks (MOFs) for gas separation and storage, commonly applied generalized gradient approximations (GGAs) exhibit self-interaction errors, which hinder the predictions of adsorption energies. We investigate the Hubbard U parameter to augment DFT calculations for full periodic MOFs, targeting a more precise modeling of gas molecule-MOF interactions, specifically for N2, CO2, and O2. We introduce a calibration scheme for the U parameter, which is tailored for each MOF, by leveraging higher-level calculations on the secondary building unit (SBU) of the MOF. When applied to the full periodic MOF, the U parameter calibrated against hybrid HSE06 calculations of SBUs successfully reproduces hybrid-quality calculations of the adsorption energy of the periodic MOF. The mean absolute deviation of adsorption energies reduces from 0.13eV for a standard GGA treatment to 0.06eV with the calibrated U, demonstrating the utility of the calibration procedure when applied to the full MOF structure. Furthermore, attempting to use coupled cluster singles and doubles with perturbative triples calculations of isolated SBUs for this calibration procedure shows varying degrees of success in predicting the experimental heat of adsorption. It improves accuracy for N2 adsorption for cases of overbinding, whereas its impact on CO2 is minimal, and ambiguities in spin state assignment hinder consistent improvements of O2 adsorption. Our findings emphasize the limitations of cluster models and advocate the use of full periodic MOF systems with a calibrated U parameter, providing a more comprehensive understanding of gas adsorption in MOFs.

Enhancing flame retardancy and antibacterial properties of wood veneer by promoting crosslinking in metal-organic framework structures

Decorative veneer, rotary cut from wood, serving as the outermost layer of decorative plates and is exposed to potential risks of fire hazards and bacterial growth. In this study, following the principle of eco-friendly and cost-effective, the polyamino polyether methylene phosphonate (PAPEMP) and magnesium chloride (MgCl2) were sequentially impregnated into the veneer, and then the alkaline environment was employed to facilitate the complexation, leading to the formation of cross-linked chains within the porous wood structure. Consequently, the modified wood veneer, endowed with exceptional flame retardancy, smoke suppression, antibacterial properties, and good wettability was successfully achieved. Through optimization in an alkaline environment, the modified decorative veneer exhibits a remarkable increase in limiting oxygen index from 19.7% in the pure veneer to 36.9%, coupled with a significant reduction of 19.38% in total heat release and 65.22% in total smoke release compared to the pure veneer. Additionally, the peak mass loss rate (PLMR) of the modified veneer was 66.41% lower than that of the pure veneer, and the char residue increased to 46.1%, representing a 149.19% improvement over the pure veneer. Compared with pure veneer, the wettability of modified veneer increased by 37.93%. Additionally, the tensile strength parallel to the grain of the modified veneer was enhanced by 22.09% compared to the veneer without NaOH solution treatment, and exhibits strong inhibitory effects on colony reproduction. The developed flame-retardant and antibacterial treatment processes for decorative veneers offer a novel and environmentally friendly method for utilizing precious tree veneers, suitable for a variety of precious woods, and successfully applied to decorative wooden doors and wooden fire-resistant doors.

Recent Developments in Porphyrin-Based Metal-Organic Framework Materials for Water Remediation under Visible-Light Irradiation.

Access to clean drinking water is a basic requirement, and eliminating pollutants from wastewater is important for saving water ecosystems. The porous structure and surface characteristics of metal-organic frameworks (MOFs) can function as a perfect scaffold for removing toxic compounds from wastewater. Porphyrins are promising building blocks for constructing MOFs. Porphyrin-based metal-organic frameworks (P-MOFs) have been fabricated using porphyrin ligands, metal clusters, or ions. These materials can harvest light from a wide region of the solar spectrum, and their framework morphology and physicochemical properties can be controlled by changing their peripheral subunits or metal ions. These porous crystalline materials have generated interest because of their distinctive characteristics, including large permanent porosity, interesting surface morphology, broad conformational diversity, high photostability, and semiconducting nature. This article discusses the recent progress and usefulness of P-MOFs. The fabrication procedures of P-MOFs are discussed, followed by the adsorptive and photocatalytic removal of contaminants from wastewater. The relationships between the geometries of P-MOFs and their light-harvesting and charge-transfer mechanisms for the photocatalytic degradation of pollutants are highlighted. Finally, some future perspectives and obstacles in the photodegradation usage of P-MOFs are discussed, along with feasible research directions to standardize efficient photocatalysts for improved photodegradation for water treatment.

Catalytical advantages of Hf-MOFs in benzaldehyde acetalization

The potential use of acetals as bioadditives based on sustainable feedstocks in the automotive industry is of great interest. If such feedstock is a residual stream, the process would represent a dual environmental challenge, such as the valorization of glycerol obtained as a by-product of biodiesel to produce acetals. There are just scarce works about this synthetic route due to the challenge in finding efficient catalytic converters for glycerol valorization in a single process. Herein four different Metal-Organic Frameworks (MOFs) are evaluated as heterogeneous catalysts for the acetalization reaction of benzaldehyde with methanol, specifically, two structures, MOF-808 and UiO-66, containing two structural metal ions, zirconium and hafnium. The aim of this work is to investigate the influence of the MOF structure, the metallic active sites and the reaction conditions on the catalytic performance of this acetal production-type reaction. Furthermore, the recyclability of the catalyst is evaluated, and a potential reaction mechanism is suggested. As relevant results, Hf-MOFs showed higher benzaldehyde conversion than Zr-based ones, and significant improvements in reaction conditions were achieved, such as a significant reduction in catalyst loading of 99.6 % using UiO-66-Hf, and an optimization of reagent ratios reducing methanol consumption by 50 % for a 92 % of benzaldehyde conversion. The Brønsted character of UiO-66-Hf seems to enhance the reaction rate more than the metal center accessibility and larger pore volumes offered by MOF-808.

Water-Stable High-Entropy Metal-Organic Framework Nanosheets for Photocatalytic Hydrogen Production.

Metal-organic frameworks (MOFs) have emerged as promising platforms for photocatalytic hydrogen evolution reaction (HER) due to their fascinating physiochemical properties. Rationally engineering the compositions and structures of MOFs can provide abundant opportunities for their optimization. In recent years, high-entropy materials (HEMs) have demonstrated great potential in the energy and environment fields. However, there is still no report on the development of high-entropy MOFs (HE-MOFs) for photocatalytic HER in aqueous solution. Herein, the authors report the synthesis of a novel p-type HE-MOFssingle crystal (HE-MOF-SC) and the corresponding HE-MOFsnanosheets (HE-MOF-NS) capable of realizing visible-light-driven photocatalytic HER. Both HE-MOF-SC and HE-MOF-NS exhibit higher photocatalytic HER activity than all the single-metal MOFs, which are supposed to be ascribed to the interplay between the different metal nodes in the HE-MOFsthat enables more efficient charge transfer. Moreover, impressively, the HE-MOF-NS demonstrates much higher photocatalytic activity than the HE-MOF-SC due to its thin thickness and enhanced surface area. At optimum conditions, the rate of H2 evolution on the HE-MOF-NS is ≈13.24 mmol h-1 g-1, which is among the highest values reported for water-stable MOF photocatalysts. This work highlights the importance of developing advanced high-entropy materials toward enhanced photocatalysis.

2D Copper–Porphyrin Metal–Organic Framework Nanosheet‐Photosensitized TiO2 for Efficiently Broadband Light‐Driven Conversion of CO2 to CH4

The effective utilization of light is crucial in the use of the solar energy for CO2 conversion into valuable fuels and chemicals, in which improving the photocatalytic materials’ capacity to absorb light is a key. Herein, a 2D copper–porphyrin metal−organic framework (MOF)‐photosensitized titania, TiO2/Zn–CuTCPP, is reported, which can absorb wide range of light and photoreduce CO2 with high efficiency under full spectrum irradiation. Fluorescence spectral analysis elucidates the relationship between the photocatalytic activity and the electron–hole separation efficiency. In addition, mechanistic information obtained from electron paramagnetic resonance and in situ infrared analyses demonstrates that the presence of Cu–N4 site in the MOF structure is conducive to the generation of hydrogen free radicals (•H), which plays a key role in the formation of intermediates, thus facilitating the hydrogenation in the reaction process. Consequently, TiO2/Zn–CuTCPP significantly enhances the photocatalytic conversion of CO2 into CH4 with a yield 14 times higher than that of P25.