Host-Guest Structure Enabling Electrocatalytic Hydrogen Evolution Performance by POM@TM-BDC Composites

Developing economical, efficient, and earth-rich electrocatalysts for hydrogen evolution reaction (HER) is quite challenging and ideal. We propose that [P2W18O62]6- as the guest, due to its excellent reversible 18 electron-transfer capacity and redox properties, and then TM-BDC (TM = Ni, Co, Fe, BDC = 1,4-benzene-dicarboxylate) as the host make [P2W18O62]6- packaged and not escape due to its porous structure. Benefiting from strong redox-competent interactions between [P2W18O62]6- and porous structures of TM-BDC and full exposure of abundant active sites, three {P2W18}@TM-BDC composites exhibited excellent HER activity, with {P2W18}@Ni-BDC requiring 198 mV (overpotentials) and 104 mV/dec (Tafel slope) for HER. More importantly, three {P2W18}@TM-BDC composites show excellent stability, with the voltage remaining nearly constant for 24 h. Meanwhile, the linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) curves of three {P2W18}@TM-BDC overlap well with the initial curve after the stability test. Our work offers a promising strategy for synthesizing high-performance electrocatalysts and broadens the scope of nonprecious metal composite material preparation.

Increased CO2/N2 selectivity by stepwise fluorination in isoreticular ultramicroporous metal-organic frameworks

Exploration of porous adsorbents with high CO2/N2 selectivity is of great significance for reducing CO2 content in the atmosphere. In this study, a series of isoreticular ultramicroporous fluorinated metal-organic frameworks (MOFs) were prepared to explore the benefits of fluorinated ultramicropores in improving CO2/N2 selectivity. Gas adsorption measurements revealed that the increase in the number of fluorine atoms in a ligand molecule leads to the increased CO2 uptakes and CO2/N2 selectivity. Theoretical calculations indicate that the interaction between the fluorine atoms and adsorbed CO2 molecules enhances the CO2-philicity, offering useful insight into the improvement of CO2/N2 selectivity in isoreticular frameworks.

Hydrogen storage in M(BDC)(TED)0.5 metal-organic framework: physical insights and capacities

Finding renewable energy sources to replace fossil energy has been an essential demand in recent years. Hydrogen gas has been becoming a research hotspot for its clean and free-carbon energy. However, hydrogen storage technology is challenging for mobile and automotive applications. Metal-organic frameworks (MOFs) have emerged as one of the most advanced materials for hydrogen storage due to their exceptionally high surface area, ultra-large and tuneable pore size. Recently, computer simulations allowed the designing of new MOF structures with significant hydrogen storage capacity. However, no studies are available to elucidate the hydrogen storage in M(BDC)(TED)0.5, where M = metal, BDC = 1,4-benzene dicarboxylate, and TED = triethylenediamine. In this report, we used van der Waals-dispersion corrected density functional theory and grand canonical Monte Carlo methods to explore the electronic structure properties, adsorption energies, and gravimetric and volumetric hydrogen loadings in M(BDC)(TED)0.5 (M = Mg, V, Co, Ni, and Cu). Our results showed that the most favourable adsorption site of H2 in M(BDC)(TED)0.5 is the metal cluster-TED intersection region, in which Ni offers the strongest binding strength with the adsorption energy of -16.9 kJ mol-1. Besides, the H2@M(BDC)(TED)0.5 interaction is physisorption, which mainly stems from the contribution of the d orbitals of the metal atoms for M = Ni, V, Cu, and Co and the p orbitals of the O, C, N atoms for M = Mg interacting with the σ* state of the adsorbed hydrogen molecule. Noticeably, the alkaline-earth metal Mg strongly enhanced the specific surface area and pore size of the M(BDC)(TED)0.5 MOF, leading to an enormous increase in hydrogen storage with the highest absolute (excess) gravimetric and volumetric uptakes of 1.05 (0.36) wt% and 7.47 (2.59) g L-1 at 298 K and 7.42 (5.80) wt% and 52.77 (41.26) g L-1 at 77 K, respectively. The results are comparable to the other MOFs found in the literature.

Efficient Adsorption of Methylene Blue Using a Hierarchically Structured Metal-Organic Framework Derived from Layered Double Hydroxide

The growing concerns about environmental pollution, particularly water pollution, are causing an increasing alarm in modern society. One promising approach to address this issue involves engineering existing materials to enhance their effectiveness. A one-step solvothermal reconstruction approach was used to build an eco-friendly two-dimensional (2D) AlNiZn-LDH/BDC MOF composite. The characterizations confirm the formation of a metal-organic framework (MOF) at the layered double hydroxide (LDH) surface. The resulting synthesized material, 2D AlNiZn-LDH/BDC MOF, demonstrated remarkable efficacy in decontaminating methylene blue (MB), a model cationic dye found in water systems. The removal performance of 2D AlNiZn-LDH/BDC MOF was significantly higher than that of pristine 2D AlNiZn-LDH. This improvement shows the potential to increase the adsorption capabilities of nanoporous LDH materials by incorporating organic ligands and integrating meso-/microporosity through MOF formation on their surfaces. Furthermore, their kinetic, isothermal, and thermodynamic studies elucidated the adsorption behavior of this composite material. The results of synthesized MOF showed excellent removal efficiency (92.27%) of 10 ppm of MB aqueous solution as compared to pristine LDH. Additionally, the as-synthesized adsorbent could be regenerated for six successive cycles. This method holds promise for the synthesis of novel and highly effective materials to combat water pollution, laying the groundwork for potential advancements in diverse applications.

Microporous Fluorinated MOF with Multiple Adsorption Sites for Efficient Recovery of C2H6 and C3H8 from Natural Gas

Purifying C2H6/C3H8 from a ternary natural gas mixture through adsorption separation is an important but challenging process in the petrochemical industry. To address this challenge, the industry is exploring effective strategies for designing high-performance adsorbents. In this study, we present two metal-organic frameworks (MOFs), DMOF-TF and DMOF-(CF3)2, which have fluorinated pores obtained by substituting linker ligands in the host material. This pore engineering strategy not only provides suitable pore confinement but also enhances the adsorption capacities for C2H6/C3H8 by providing additional binding sites. Theoretical calculations and transient breakthrough experiments show that the introduction of F atoms not only improves the efficiency of natural gas separation but also provides multiple adsorption sites for C2H6/C3H8-framework interactions.

Enhancing Hydrogen Adsorption Capacity of Metal Organic Frameworks M(BDC)TED0.5 through Constructing a Bimetallic Structure

Metal organic frameworks (MOFs) have promising application prospects in the field of hydrogen storage. However, the successful application of MOFs in the field is still limited by their hydrogen storage capacity. Herein, a series of M _x M_1-x (BDC)TED_0.5 (M = Zn, Cu, Co, or Ni) with a bimetallic structure was constructed by introducing two metal ions in the synthesis process. The results of X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma showed that the bimetallic structure with different content ratios can be stably constructed by a hydrothermal method. Among them, the Cu-based bimetal MOFs Cu_0.625Ni_0.375(BDC)TED_0.5 exhibited the best hydrogen storage capacity of 2.04 wt% at 77 K and 1 bar, which was 22% higher than that of monometallic Ni(BDC)TED_0.5. The enhanced hydrogen storage capacity can be attributed to the improved specific surface area and micropore volume of bimetal MOFs by introducing an appropriate amount of bimetallic atoms.

Hierarchical Co@C-N synthesized by the confined pyrolysis of ionic liquid@metal–organic frameworks for the aerobic oxidation of alcohols

Co@C-N with hierarchical pores and highly active sites is synthesized by the pyrolysis of an ionic liquid@metal–organic framework.

Chemical fixation of CO2 into cyclic carbonates catalyzed by bimetal mixed MOFs: the role of the interaction between Co and Zn

Catalytic conversion of carbon dioxide into cyclic carbonates in the presence of bimetal mixed MOFs.

Nanoscale nickel metal organic framework decorated over graphene oxide and carbon nanotubes for water remediation

In this report, highly crystalline and well-dispersed nano-sized nickel metal organic framework (MOFs) was decorated over graphene oxide (GO) and carbon nanotubes (CNTs) platforms to form hybrid nanocomposites. These as-synthesized hybrid nanocomposites were synthesized through a one-pot green solvothermal method. The prepared nanocomposites were characterized by SEM, TEM, EDS, XRD, FT-IR, Raman and TGA techniques. XRD analysis revealed the crystalline structure of the hybrid nanocomposites. Morphological and elemental studies also verified successful decoration of nickel-benzene dicarboxylate (Ni-BDC) MOFs over GO and CNT platforms. Chemical analysis collected through IR, and thermal analysis collected through TGA technique, illustrated the presence of all the components in the hybrid nanomaterials. Methylene blue (MB) was used as a model organic pollutant to analyze the adsorption capacity of the prepared nanocomposites. According to the findings, a strong interaction exists between the MB molecule and the developed adsorbents at which due to the synergistic effect, the hybrid nanocomposites show several times higher adsorption capacity compared to that of parent materials. This improvement can be due to several reasons: high surface area of the MOFs in the composites resulting from the smaller size of MOFs, presence of the pores formed between the MOFs and the platforms and different morphological characteristic of Ni-BDC MOFs in hybrid nanocomposites, compared to bare Ni-BDC MOFs. Furthermore, the isotherm and kinetic studies revealed that the adsorption of MB onto the newly prepared adsorbents could best be explained by the Langmuir and Pseudo-second order kinetic models. A regeneration study demonstrated the highly stable nature of the hybrid nanocomposites.

Enhanced mechanical properties of a metal-organic framework by polymer insertion

The mechanical strength of metal-organic frameworks (MOFs) is highly relevant for their practical applications. In this research, we show that encapsulation of polymer chains into MOF nanochannels can effectively restrain the breakage of coordination bonding in MOFs and inhibit the amorphization under high physical pressure. The hardness of single MOF crystals was greatly improved, which depended on the direction of the inserted polymers, as revealed by nanoindentation analysis. Insertion of polymer chains did not influence the crystal structure of MOFs, which indicates that this approach should be highly promising for improving the mechanical properties of MOFs.

Synthesis, characterization, and thermal properties of cobalt(ii) compounds with guanidinate ligands

The synthesis, characterization, and thermal properties of cobalt(ii) compounds with guanidinate ligands and their potential as CVD precursors are reported.

Highly thermally stable heterogeneous catalysts: study of 0D and 3D porphyrinic MOFs

Porphyrin-based MOFs as heterogeneous catalysts show high catalytic activity, recyclability and selectivity towards alkene oxidation.

Oxidation of benzyl alcohol over metal organic frameworks M-BTC (M = Co, Cu, Fe)

Co-BTC showed high catalytic activity and selectivity in the oxidation of benzyl alcohol with air as the oxidant.

Tuneable nature of metal organic frameworks as heterogeneous solid catalysts for alcohol oxidation

This Feature article describes on the recent developments in the use of metal organic frameworks as heterogeneous solid catalysts for the selective alcohol oxidation by either tuning the actives sites around the metal centre, or anchoring them on the ligands or using the pores to embed metal nanoparticles inside.