Porous MOF Research Articles

Porous Pd-Loaded IRMOF-9 as Highly Efficient Recyclable Material Towards the Reduction of Nitroaromatics in Aqueous Media.

Nitroaromatic compounds (NACs) cause severe hazardous impacts on human health as well as on the environment. Therefore, there is dire need to develop a robust material to reduce the toxicity of these organic pollutants. In this regard, our group developed a series of porous MOF materials viz., Pdx@IRMOF-9 (x=2 %, 5 % and 10 %) by loading different concentration of Pd(II) on IRMOF-9 and explored them towards reduction of different nitroaromatic compounds. Pd10%@IRMOF-9showed ~30 % greater efficiency for the reduction of 4-NP as compared to Pd2%@IRMOF-9. Pd10%@IRMOF-9showed excellent reduction ability (>85 %) towards 4-NP, 2-NP, 2-NA, 3-NA and 2,4-DNPH. The kinetic studies indicates that the reduction follows the pseudo-first-order kinetics. Moreover, the rate constant value for reduction of 3-NA was ~9 times higher than that of 2-NP. Based on the kinetic parameters, the t1/2 values for all the nitroaromatics have been calculated. The kinetic parameters, Km and Vmax have been calculated from double reciprocal Lineweaver-Burk plot and found to be 65.984 μM and 116×10-6 Mmin-1 respectively. Pd10%@IRMOF-9showed excellent recyclability towards the reduction of 4-NP for few consecutive cycles without any remarkable loss in its activity. Thus, highly efficient, porous and robust material for the reduction of nitroaromatic compounds in aqueous media have been demonstrated.

Ambidextrous approach in action: Mg(OMe)2-doped hierarchical porous zirconium MOFs for decontaminating toxic chemical agents in nonbuffered systems

Utilizing a ligand-truncation strategy, a hierarchically porous structure was engineered within MOF-808, designated as HP-MOF-808. Furthermore, Mg(OMe)2 doping yielded HP-MOF-808@Mg(OMe)2, materials with both hierarchical porosity and basic character, for decontamination of two types of toxic chemical agents in nonbuffered solutions. In aqueous solution, the HP-808-2 exhibited decontamination rate constants for dimethyl-4-nitrophenyl phosphate (DMNP) and the nerve agent soman (GD) that were 3.13 and 1.98 times higher than MOF-808, respectively. The decontamination half-lives of HP-808-2@Mg(OMe)2 1:2 for DMNP and GD were further reduced by 13.87 and 36.82 times compared to HP-808-2. The material retains its decontamination efficacy for DMNP even after 60-days exposure in air and maintains structural integrity in solvents devoid of labile hydrogen for at least 24 h. In methanol, HP-808-2@Mg(OMe)2 achieved 100% DMNP decontamination in 25 min, outperforming HP-808-2 at 31.8%, marking it as the fastest DMNP decontamination material in methanol. Theoretical simulations confirmed the experimental findings, clearly demonstrating the energy changes during reactions with various nucleophiles and revealing the degradation process and mechanism of DMNP on the active sites of MOFs. Moreover, these materials rapidly degraded 2-chloroethyl ethyl sulfide (CEES) through hydrolysis, dehydrohalogenation, and heterolytic cleavage, demonstrating great potential for dual decontamination of toxic chemical agents in unbuffered systems.

Ultrastable hierarchically porous nucleotide-based MOFs and their use for enzyme immobilization and catalysis

Immobilization of free enzymes facilitates their recovery and reuse, while also enhances their enzymatic characteristics. Hierarchically porous metal-organic frameworks (HP-MOFs) are promising candidates for enzyme immobilization. However, fabrication of HP-MOFs with more kinds of components as ligands is still a challenge. Herein, ultrastable crystalline MOFs with micro-, meso- and macroporous structure were constructed using guanosine 5′-monophosphate (GMP) as organic ligand through templated emulsification method. HP-MOFs crystals with the near rhomb-like, rod-like and slab-like morphology were interestingly obtained from Zn2+, Cu2+ and Cd2+ respectively. The HP-MOFs immobilized enzymes exhibited an enhanced enzymatic activity and stability. In addition, the immobilized CALB (Candida antarctica lipase B) showed great glycerolysis and esterification performances for glycerides preparation, with diacylglycerols (DAG) content over 60 wt% and triacylglycerols (TAG) content over 90 wt% obtained respectively from glycerolysis and esterification. Moreover, it retained 82.32 % of its initial glycerolysis activity after six cycles of reuse in glycerolysis. The present study will provide clues and show new horizons to explore new organic ligands for HP-MOFs fabrication, as well as to expand the applications of HP-MOFs and their supported enzymes.

Remarkable C2H4 separation at ambient condition with a chemically sturdy porous MOF through pore confinement

An alternate to energy intensive cryogenic high-pressure distillation process for the separation of ethylene from its gas mixture with ethane is highly appealing. In this contribution, a highly chemically robust microporous MOF named 1 (stable in water, boiling water, and pH = 2–11) has been employed for preferential ethylene sorption with excellent selectivity. The simulation study disclosed the selective pore confinement of ethylene through non-covalent interactions with the amine and carboxylate sites of the framework backbone. Column breakthrough study unveiled 15.2 and 24.8 L kg−1 ethylene production per cycle at 298 K for the 50:50 and 90:10 (v/v) C2H4/C2H6 mixture which places this MOF as one of the best physisorbent material for ethylene separation. Industrial applicability is tested in a hydrous environment (displaying unaltered performance) as well as its regenerability under vacuum or mild heating for successive cyclic operations.

Construction of Ag/AgCl@MIL-53(Fe): Achieving Efficient Photocatalytic Water Oxidation via the Plasma-Phase Silver and Heterojunction Synergistic Effect

The development of highly efficient water oxidation catalysts is a bottleneck in achieving artificial photosynthesis, as water oxidation is a complex process involving multiple electron and proton transfers. To further improve the photocatalytic water oxidation performance of MIL-53(Fe), a series of Ag/AgCl@MIL-53(Fe) samples with different Fe:Ag ratios were synthesized by hydrothermal methods and used in the photocatalytic water oxidation reactions. XRD characterization showed the successful preparation of Ag/AgCl@MIL-53(Fe) heterostructure catalysts. The reaction results showed that sample AAM-2 (Fe:Ag=5:1) had the best photocatalytic water oxidation performance, with the highest TOF value of 0.14 mmol/(g·s) and quantum efficiency of 39.0 % under the conditions of catalyst mass of 1 mg and pH=9.0 for boric acid-borax buffer solution. Measurements of photocurrent indicated that the AAM-2 samples doped with Ag/AgCl had higher photocurrent densities, thus improving the photocatalytic performance. This provides new insights for constructing highly efficient porous MOFs catalysts.

The crystal engineering of 3d-metal with two tetrazole-phenyl-carboxylate linkers and multiple post-synthetic metal exchange

Ligand with mixed-groups contributes to the construction of special structure motif with novel properties, yet it is challenging to understand and regulate the competitive coordination of different functional groups toward metal ions. Herein, the crystal engineering for MOF construction from two linear di-topic linkers of 4-(1H-tetrazol-5-yl)benzoic acid (H2tzba) and the longer 4′-(1H-tetrazol-5-yl)-[1,1′-biphenyl]-4-carboxylic acid (H2tzbba) featuring dual groups of phenyl-carboxylate and tetrazole, with three typical 3d metal ions (Mn2+, Fe2+ and Zn2+) were investigated. A series of five new MOFs, that are [Mn3(tzba)3(dmf)4]·11dmf (1, dmf = N,N-Dimethylformamide), [Mn(tzba)(H2O)] (2), [Zn2(tzba)2(dmf)]·0.5dmf (3), [Fe2(tzba)2(dmf)]·0.5dmf (4) and [Zn2(tzbbz)(gac)(dmf)2]·1.5dmf (5), were synthesized under solvothermal reactions. The modified solvent template and temperature effects lead to 3D framework of 1 (dmf solution under 433 K) with [Mn3(tz)3(COO)3] nodes and 1D hexagonal channels, while the 2 (water solution under 373 K) posssesses compact pillared-layer motif from [Mn2(tz)2] nodes. Under changed metal salt reactents but same solvent of dmf, the generated 3 and 4 have isoreticular and porous pillared-layer structure constituted of [M2(COO)2] nodes. The use of tzbba coupled with a crucial auxiliary ligand of glycollic acid, leads to 5 as porous pillared-layer MOFs with 1D rounded channels. The porous flexible skeleton of 1 constructed from [Mn3] node with four coordinated dmf facilitates post-synthetic metal exchange of the Mn2+ by radius similar metal ions following priority of Cu2+ < Zn2+ < Ni2+< Co2+, with maximum exchange percentage ranging from 17 % to 69 %. Time dependent ICP-AES analysis revealed the quite wide feasible solvents for post-synthetic metal exchange, as well as the fine control on substituting degree based on soaking temperature and time. Particularly, the compatible introduce of four different metal ions support the potential of preparing bi-, tri-, tetra- and penta- metal MOF crystals, that can not be obtained by traditional solvothermal reactions.

The synthesis of multi-level porous MOF composite materials with different MOF contents

To address the inherent limitations of current MOF synthesis, where pore size is restricted to micropores or small mesopores, we successfully synthesized MOF composite materials with well-developed porous structures using a self-template approach. These pores encompass not only the intrinsic micropores or small mesopores of MOFs but also the template-induced large pores. During the experimental process, we achieved the synthesis of composite materials with varying MOF contents by modifying experimental conditions. Through this design, we not only achieved selective adsorption of guest molecules but also significantly increased the porosity, thereby enhancing the mass transfer efficiency of guest molecules and the utilization rate of materials. This research breakthrough offers new insights and solutions for addressing critical issues in fields such as gas separation, energy storage, and catalysis.

Metal-organic framework derived heterostructured phosphide bifunctional electrocatalyst for efficient overall water splitting

Developing high active and stable cost-effective bifunctional electrocatalysts for overall water splitting to produce hydrogen is of vital significance in clean and sustainable energy development. This work has prepared a novel porous unreported MOF (Ni-DPT) as a precursor to successfully synthesize a non-noble bifunctional NiCoP/Ni12P5@NF electrocatalyst through doping strategy and interface engineering. This catalyst is constructed by layered self-supporting arrays with heterojunction interface and rich nitrogen-phosphorus doping. Structural characterizations and the density function theory (DFT) calculations confirm that the interface effect of NiCoP/Ni12P5 heterojunction can regulate the electronic structure of the catalyst to optimize the Gibbs free energy of hydrogen (ΔGH*); simultaneously, the defect-rich layered nanoarrays can expose more active sites, shorten mass transfer distance, and generate a self-supporting structure for in-situ reinforcing the structural stability. As a result, this NiCoP/Ni12P5@NF catalyst exhibits favorable electrocatalytic performance, which simply needs overpotentials of 100 mV for HER and 310 mV for OER, respectively, at a current density of 10 mA·cm−2. The anion exchange membrane electrolyzer assembled with this NiCoP/Ni12P5@NF as both anode and cathode catalysts can operate stably for 200 h at a current density of 100 mA·cm−2 with an insignificant voltage decrease. This work may provide some inspiration for the further rational design of inexpensive non-noble multifunctional electrocatalysts and electrode materials for water splitting to generate hydrogen.

Enhanced osmotic power generation through anodic electrodeposited MOFs@MXene heterostructured nanochannels

Nanochannel membranes exhibit significant potential in osmotic energy generation, however, achieving an optimal balance between ion selectivity and flux remains challenging. Herein, heterostructured MOFs@MXene nanochannels were prepared via an optimized anodic electrodeposition method, which demonstrated a significant advancement in osmotic energy generation. The unique oriented porous MOFs expanded the interlayer spacing of MXene. The inherent negative charged surface of MXene fostered a synergistic effect that substantially enhanced ion selectivity and flux, achieving a significant diffusion potential of 340.2 mV. These improvements enable the membranes to achieve an impressive power density output of 25.3 W/m2 at a concentration gradient of 106 in KCl and 17.2 W/m2 at a gradient of 500 in NaCl. Furthermore, the membranes demonstrate an energy conversion efficiency of up to 45.1 %. Such structural and functional advancements underscore the potential of these heterostructured nanochannels in robust and efficient osmotic power generation, paving the way for applications in sustainable energy technologies.

Constructing local nanomolecular trap in a scalable, low-cost, and ultramicroporous metal–organic framework for efficient capture of greenhouse gases SF6 and CO2

The capture of sulfur hexafluoride (SF6) and carbon dioxide (CO2) is an important but challenging task for reducing greenhouse gas emission and thereby diminishing negative impacts of global climate change. Herein, we integrated local nanomolecular traps into an inexpensive cobalt-based metal–organic framework (MOF, namely GNU-3) with suitable pore sizes and functional pore surfaces for capturing greenhouse gases. Activated GNU-3a showed good adsorption and separation properties for SF6 and CO2. Especially for SF6, GNU-3a displayed the high SF6/N2 (10:90, v/v) selectivity of 317.6 and SF6 uptake capacity of 2.63mmol/g at 298 K and 1.0 bar. Grand canonical Monte Carlo simulations and first-principles dispersion-corrected density functional theory calculations identified that gas molecules were favorably trapped in polyaromatic ring functionalized channel centers and nanomolecular traps of pore walls by the strong hydrogen bond interactions. Excellent breakthrough results recommend practical separating properties of GNU-3a for binary SF6/N2 and CO2/N2 mixtures, and ternary SF6/CO2/N2 mixtures. Moreover, benefitting from superior features of cheap raw materials and large-scale synthesis, GNU-3 is expected to be applied to practical industrial scenarios. This work may provide insights into constructing prospectively industrial porous MOF adsorbents with optimal pore structures for greenhouse gas capture.

Facile Preparation of TiO2NTs/Au@MOF Nanocomposites for High-Sensitivity SERS Sensing of Gaseous VOC.

Surface-enhanced Raman spectroscopy (SERS) is a promising and highly sensitive molecular fingerprint detection technology. However, the development of SERS nanocomposites that are label-free, highly sensitive, selective, stable, and reusable for gaseous volatile organic compounds (VOCs) detection remains a challenge. Here, we report a novel TiO2NTs/AuNPs@ZIF-8 nanocomposite for the ultrasensitive SERS detection of VOCs. The three-dimensional TiO2 nanotube structure with a large specific surface area provides abundant sites for the loading of Au NPs, which possess excellent local surface plasmon resonance (LSPR) effects, further leading to the formation of a large number of SERS active hotspots. The externally wrapped porous MOF structure adsorbs more gaseous VOC molecules onto the noble metal surface. Under the synergistic mechanism of physical and chemical enhancement, a better SERS enhancement effect can be achieved. By optimizing experimental conditions, the SERS detection limit for acetophenone, a common exhaled VOC, is as low as 10-11 M. And the relative standard deviation of SERS signal intensity from different points on the same nanocomposite surface is 4.7%. The acetophenone gas achieves a 1 min response and the signal reaches stability in 4 min. Under UV irradiation, the surface-adsorbed acetophenone can be completely degraded within 40 min. The experimental results demonstrate that this nanocomposite has good detection sensitivity, repeatability, selectivity, response speed, and reusability, making it a promising sensor for gaseous VOCs.

Preparation and sensing performance of chiral carbon Dot@MOF electrode material

Abstract Chirality is a ubiquitous phenomenon in nature. The identification of chiral compounds has important theoretical significance and application prospects in many fields such as biology, medicine, and food. This paper proposes an innovative approach to differentiate enantiomers by using the synergistic effect of chiral MOFs and CDs through electrochemiluminescence. The results demonstrate that CDs@[Zn(D-cam)(phen)(H2O)]n exhibit higher electrochemiluminescent response towards L/D-Trp, enabling the detection of Trp enantiomers. This research suggests that selective recognition of amino acid enantiomers can be achieved through ECL-based nanocomposites of CDs and porous MOFs.

A synergistic polyelectrolytes-Zr-MOF hydrated construction graphene oxide nanofiltration with enhanced dye wastewater remediation

In recent years, developing an efficient nanofiltration membrane had been a thorny challenge for dye/salt wastewater purification. In this study, a novel graphene oxide-based nanofiltration membrane (GO/UiO@S-GO-8) was constructed by intercalating the synergistic polyelectrolytes-Zr-MOF hydrated construction (UiO@S-GO) into GO nanosheets. Here, combining the hydrophilic high-density anionic sulfonic groups (SO3-) with cationic amino groups (-NH2), GO-based nanofiltration membrane demonstrated outstanding separation ability, anti-pollution performance and structure stability. Compared to pure GO membrane, benefiting by effective expansion of graphene layer spacing from intercalation effect of UiO@S-GO, the water permeance of GO/UiO@S-GO-8 membrane increased to 8 times (about 66.3 ± 1.5 L m−2 h−1 bar−1). Importantly, the permeances of various dyes wastewater also reached up to 65.1 ± 1.8 L m−2 h−1 bar−1 at the high removal rate (exceeding 99.4%). Furthermore, strong hydratability of polyelectrolytes and hard porous crystal constructed the robust anti-fouling micro/nano rough structures onto the membrane surface, which made flux recovery rate (FRR) of GO/UiO@S-GO-8 enhanced to 96.7 ± 1.3%. Remarkably, the salt-resistant behavior of the polyelectrolytes and porous MOF could maintain the stability of the membrane filtration channels, the GO/UiO@S-GO-8 membrane could realize efficient removal rate of dyes (over 98%) faced the complex dye wastewater with different salt concentrations. Meanwhile, the GO/UiO@S-GO-8 membrane also could maintain the high permeance (46.7 ± 1.5 L m−2 h−1 bar−1) as well as excellent removal rate (97.2 ± 1.4%) after 10 cycle experiments. Hence, the GO/UiO@S-GO-8 nanofiltration membrane with Polyelectrolytes-Zr-MOF hydrated construction possessed a broad application inspiration in the purification of high-salt/dye wastewater.

Porous layered MOFs (Cu-BDC) for highly efficient uranyl-ion adsorption from aqueous solutions

Porous layered MOFs (Cu-BDC) for highly efficient uranyl-ion adsorption from aqueous solutions

Porous Triple-Layered Supramolecular Heptazine-Based MOF with High Concentration of Binding Sites for Selective Separation of Methane

Porous Triple-Layered Supramolecular Heptazine-Based MOF with High Concentration of Binding Sites for Selective Separation of Methane

Efficient heck and Suzuki-Miyaura cross-coupling reactions catalyzed by heterogeneous Pd NPs-decorated porous MOF catalysts under mild conditions

Carbon-carbon coupling reactions are extremely interesting for a variety of applications, including pharmaceuticals and biologically active compounds. In this study, we investigated the utilization of functionalized MIL-101 porous MOF for stabilizing palladium nanoparticles (NPs) and examined their catalytic performance in the cross-coupling reaction of aryl halides with phenylboronic acid and methyl acrylate under mild conditions. To achieve this, MIL-101(Al) was synthesized using a solvothermal method, followed by functionalization with environmentally friendly l-Cysteine (CYS). Subsequently, the MIL-101(Al)-CYS compound was immersed in an ethanolic solution of palladium and stirred overnight. The catalyst exhibited remarkable efficiency (over 90 %) in Suzuki and Heck cross-coupling reactions, demonstrating excellent activity and recyclability. The reactions were conducted in polyethylene glycol 200 (PEG 200), a green reaction medium, at temperatures of 70 °C and 60 °C, with Pd loadings of 0.22 and 0.08 mol%, respectively. MOF-based catalysts, owing to their highly tunable structures and porosity, hold great promise as heterogeneous catalysts in organic reactions.

Enhancing proton conduction of MOF-74(Co) by encapsulating NH3 molecules

The functional design of efficient and stable proton exchange membrane materials is an important research direction in the field of proton exchange membrane fuel cells (PEMFCs). In this work, ammonia molecules were successfully encapsulated into the one-dimensional pores of MOF-74(Co) through fumigation with ammonia vapor. Alternating current (AC) impedance tests showed that the proton conductivity of NH3 modified NH3@ MOF-74(Co) reaches an impressive value of 6.8 × 10−3 S/cm, being 10000 times that of the pristine MOF-74(Co) at 98% relative humidity (RH) and 50 °C. Various and abundant hydrogen bonds can improve the proton conduction of NH3 modified compound. This strategy provides an efficient and convenient way to construct high proton conducting porous MOFs materials by attaching NH3 molecules.

Ultrasmall Pd nanocrystals confined into Co-based metal organic framework-decorated MXene nanoarchitectures for efficient methanol electrooxidation

The natural scarcity and insufficient utilization of noble metal-based catalysts bring a heavy block in the way of the widespread applications of direct methanol fuel cells. Herein, we propose a feasible bottom-up approach to the construction of ultrasmall Pd nanocrystals confined into Co-based metal organic framework-decorated Ti3C2Tx MXene (Pd/MOF-MX) nanoarchitectures via a controllable solvothermal process. The ultrathin MXene nanolamellas and porous Co-based MOFs constitute an ideal hybrid carrier with high electron conductivity and large accessible surface areas, which not only facilitates the size restriction and uniform dispersion of Pd nanocrystals, but also ameliorates their intrinsic catalytic activity through the direct electronic interactions. By virtue of the pronounced synergistic coupling effects, the newly-developed Pd/MOF-MX nanoarchitectures exhibit markedly enhanced electrocatalytic properties towards the methanol oxidation reaction, including a large electrochemically active surface area of 116.7 m2 g−1, a high mass activity of 1700.4 mA mg−1 as well as a satisfactory long-term durability, which are superior to those of traditional Pd electrocatalysts anchored on carbon blacks, carbon nanotubes, graphene, and undecorated MXene matrixes.

Temperature-Controlled Synthesis of Trimodal Hierarchically Porous MOFs with Variable Core–Shell Configurations

Temperature-Controlled Synthesis of Trimodal Hierarchically Porous MOFs with Variable Core–Shell Configurations

Thermal conductivity enhancement and shape stability of composite phase change materials using MIL-101(Cr)-NH2/expanded graphite/multi-walled carbon nanotubes

Low heat conductivity and leakage much restrict the effective use of phase changing materials (PCMs) in heat energy management. Here, an expanded graphite (EG)/ multi-walled carbon nanotube (MWCNT) / metal organic framework (MOF: MIL-101(Cr)-NH2) composite was developed to solve these issues. The porous MOF can avoid the loss of liquid paraffin wax (PW). The heat conductivity of composite PCMs (CPCMs) was improved using EG/MWCNT with a mass ratio of 4:1. The thermophysical properties, heat stability and chemical compatibility of CPCMs were comprehensively investigated. Results demonstrate the successful preparation of CPCMs without any chemical reaction. The MOF (35 %)/EG(4 %)/MWCNT(1 %)/PW(60 %) CPCM exhibits superior thermophysical properties and its melting enthalpy (74.59 J/g) is near the theoretical level after 500 heating/cooling cycles. It exhibits a 792 % increment in heat conductivity from pure PW.