Guest Cation Functionalized Metal Organic Framework for Highly Efficient C2H2/CO2 Separation.

The removal of carbon dioxide (CO2) from acetylene (C2H2) production is critical yet difficult due to their similar physicochemical properties. Despite extensive research has been conducted on metal-organic frameworks (MOFs) for C2H2/CO2 separation, approaches to designing functionalized MOFs remain limited. Enhancing gas adsorption through simple pore modification holds great promise in molecular recognition and industrial separation processes. This study proposes a guest cation functionalization strategy using the anionic framework SU-102 as the prototype material. Specifically, the guest cation Li+ is introduced into the skeleton by ion exchange to obtain SU-102-Li+. This strategy generates strong interactions between Li+ and gas molecules, thereby elevating C2H2 uptake to 49.18 cm3 g-1 and CO2 uptake to 29.88 cm3 g-1, marking 20.3% and 36.9% improvements over the parent material, respectively. In addition, ideal adsorbed solution theory selectivity calculations and dynamic breakthrough experiments confirmed the superior and stable separation performance of SU-102-Li+ for C2H2/CO2 (25 min g-1) and C2H2 productivity (1.55 mmol g-1). Theoretical calculations further reveals the unique molecular recognition mechanism between gas molecules and guest cations.

Solvent-Induced In(III)-MOFs with Controllable Interpenetration Degree Performing High-Efficiency Separation of CO2/N2 and CO2/CH4.

Herein, three In(III)-based metal-organic frameworks (In-MOFs) with different degrees of interpenetration (DOI), namely In-MOF-1, In-MOF-2, and In-MOF-3, constructed by In3+ and Y-shaped ligands 4,4',4″-s-triazine-2,4,6-triyltribenzoate (H3TATB), are successfully synthesized through the ionothermal/solvothermal method. Subsequently, three novel In-MOFs, including noninterpenetration polycatenation, 2-fold interpenetrated, and 4-fold interpenetrated structure, are employed as the platform for systematically investigating the separation efficiency of CO2/N2, CO2/CH4, and CO2/CH4/N2 mixture gas system. Among them, In-MOF-2 shows the highest CO2 uptake capacities at 298 K and simultaneously possesses the low adsorption enthalpy of CO2 (26.4 kJ/mol at low coverage), a feature desirable for low-energy-cost adsorbent regeneration. The CO2/N2 (v: v = 15/85) selectivity of In-MOF-2 reaches 37.6 (at 298 K and 1 bar), also revealing outstanding selective separation ability from flue gases and purifying natural gas, affording a unique robust separation material as it has moderate DOI and pore size. In-MOF-2 shows exceptional stability and feasibility to achieve reproducibility. Aperture adjustment makes In-MOF-2 a versatile platform for selectively capturing CO2 from flue gases or purifying natural gas.

Ultrafine Pt Nanoparticles Anchored on 2D Metal-Organic Frameworks as Multifunctional Electrocatalysts for Water Electrolysis and Zinc-Air Batteries.

Multifunctional electrocatalysts are crucial to cost-effective electrochemical energy conversion and storage systems requiring mutual enhancement of disparate reactions. Embedding noble metal nanoparticles in 2D metal-organic frameworks (MOFs) are proposed as an effective strategy, however, the hybrids usually suffer from poor electrochemical performance and electrical conductivity in operating conditions. Herein, ultrafine Pt nanoparticles strongly anchored on thiophenedicarboxylate acid based 2D Fe-MOF nanobelt arrays (Pt@Fe-MOF) are fabricated, allowing sufficient exposure of active sites with superior trifunctional electrocatalytic activity for hydrogen evolution, oxygen evolution, and oxygen reduction reactions. The interfacial Fe─O─Pt bonds can induce the charge redistribution of metal centers, leading to the optimization of adsorption energy for reaction intermediates, while the dispersibility of ultrafine Pt nanoparticles contributes to the high mass activity. When Pt@Fe-MOF is used as bifunctional catalysts for water-splitting, a low voltage of 1.65 V is required at 100 mA cm-2 with long-term stability for 20 h at temperatures (65 °C) relevant for industrial applications, outperforming commercial benchmarks. Furthermore, liquid Zn-air batteries with Pt@Fe-MOF in cathodes deliver high open-circuit voltages (1.397 V) and decent cycling stability, which motivates the fabrication of flexible quasisolid-state rechargeable Zn-air batteries with remarkable performance.

Green Synthesis of MOF-801(Zr/Ce/Hf) for CO2/N2 and CO2/CH4 Separation.

The purification of natural gas and the removal of carbon dioxide from flue gases are crucial to economize precious resources and effectively relieve a series of environmental problems caused by global warming. Metal-organic framework (MOF) materials have demonstrated remarkable performance and benefits in the area of gas separation; however, obtaining materials with high gas capacity and selectivity simultaneously remains difficult. In addition, harsh synthesis conditions and solvent toxicity have been restricted in large-scale production and industrial application. Therefore, MOF-801(Zr/Ce/Hf) was created based on the green synthesis of the MOF-801 construction unit by altering the kinds of metal salts, and the impact of three metal nodes on the performance of gas adsorption and separation was demonstrated by contrasting the three MOFs. The results showed that MOF-801(Ce) has the best CO2 adsorption capacity (3.3 mmol/g at 298 K), which also was demonstrated with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results, CO2/CH4 (ideal adsorbed solution theory (IAST) = 13.28 at 298 K, 1 bar, CO2/CH4 = 1:1, v/v), and the separation performance of CO2/N2 (IAST = 57.46 at 298 K, 1 bar, CO2/N2 = 1:1, v/v) among the group. Green synthesis of MOF-801(Zr/Ce/Hf) is an ideal candidate for flue gas separation and methane purification because of its high regeneration capacity and strong cyclic stability.

Defect engineering improves CO2/N2 and CH4/N2 separation performance of MOF-801.

A defect engineering modification method is reported to improve the CO2/N2 and CH4/N2 separation performance of MOF-801, owing to skeleton shrinkage caused by defect modification, Zr-FA0.5 shows excellent gas separation performance compared with the prototype MOF.

Superhydrophobic MOFs with enhanced catalytic activity for chemical fixation of CO2.

A general approach to prepare superhydrophobic MOFs (denoted as MOFs-CF3) through a post-decorating strategy for highly efficient chemical fixation of CO2 was demonstrated. The enhanced catalytic activity of MOFs-CF3 is attributed to a synergistic effect between the Lewis acid sites of MOFs and modification of the electron-withdrawing trifluoromethyl group, which resulted in a high CO2 enrichment capacity. The possible mechanism of cycloaddition catalyzed by the MOFs-CF3 catalyst was also proposed.

A [(M2)6L8] metal-organic polyhedron with high CO2 uptake and efficient chemical conversion of CO2 under ambient conditions.

A new metal-organic polyhedron with a high surface area of 407 m2 g-1, possessing high CO2 uptake, is reported, which is synthesized using 4-connected Cu2(CO2)4 paddle-wheel moieties and 3-connected semi-rigid tripodal carboxylates. This material possesses a high density of Cu(II) Lewis acidic sites and demonstrates excellent performance as a heterogeneous catalyst for the chemical fixation of CO2 into cyclic carbonates under ambient conditions.