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Low-concentration ethane capture is crucial for environmental protection and natural gas purification. The ideal physisorbent with strong C 2 H 6 interaction and large C 2 H 6 uptake at low-concentration level has rarely been reported, due to the large pK a value and small quadrupole moment of C 2 H 6 . Herein, we demonstrate the perfectly size matching between the ultramicropore (pore size of 4.6 Å) and ethane (kinetic diameter of 4.4 Å) in a nickel pyridine-4-carboxylate metal-organic framework (IISERP-MOF2), which enables the record-breaking performance for low concentration C 2 H 6 capture. IISERP-MOF2 exhibits the large C 2 H 6 adsorption enthalpy of 56.7 kJ/mol, and record-high C 2 H 6 uptake at low pressure of 0.01-0.1 bar and 298 K (1.8 mmol/g at 0.01 bar). Molecule simulations and C 2 H 6 -loading crystal structure analysis revealed that the maximized interaction sites in IISERP-MOF2 with ethane molecule originates the strong C 2 H 6 adsorption. The dynamic breakthrough experiments for gas mixtures of C 2 H 6 /N 2 (1/999, v/v) and C 2 H 6 /CH 4 (5/95, v/v) proved the excellent low-concentration C 2 H 6 capture performance., (© 2021 Wiley-VCH GmbH.)

Porous molecular crystals sustained by hydrogen bonds and/or weaker connections are an intriguing type of adsorbents, but they rarely demonstrate efficient adsorptive separation because of poor structural robustness and tailorability. Herein, we report a porous molecular crystal based on hydrogen-bonded cyclic dinuclear Ag I complex, which exhibits exceptional hydrophobicity with a water contact angle of 134°, and high chemical stability in water at pH 2-13. The seemingly rigid adsorbent shows a pore-opening or nonporous-to-porous type butane adsorption isotherm and complete exclusion of isobutane, indicating potential molecular sieving. Quantitative column breakthrough experiments show slight co-adsorption of isobutane with an experimental butane/isobutane selectivity of 23, and isobutane can be purified more efficiently than for butane. In situ powder/single-crystal X-ray diffraction and computational simulations reveal that a trivial guest-induced structural transformation plays a critical role., (© 2020 Wiley-VCH GmbH.)

Efficient adsorptive separation of propylene/propane (C 3 H 6 /C 3 H 8 ) is highly desired and challenging. Known strategies focus on either the thermodynamic or the kinetic mechanism. Here, we report an interesting reactivity of a metal-organic framework that improves thermodynamic and kinetic adsorption selectivity simultaneously. When the metal-organic framework is heated under oxygen flow, half of the soft methylene bridges of the organic ligands are selectively oxidized to form the more polar and rigid carbonyl bridges. Mixture breakthrough experiments showed drastic increase of C 3 H 6 /C 3 H 8 selectivity from 1.5 to 15. For comparison, the C 3 H 6 /C 3 H 8 selectivities of the best-performing metal-organic frameworks Co-MOF-74 and KAUST-7 were experimentally determined to be 6.5 and 12, respectively. Gas adsorption isotherms/kinetics, single-crystal X-ray diffraction, and computational simulations revealed that the oxidation gives additional guest recognition sites, which improve thermodynamic selectivity, and reduces the framework flexibility, which generate kinetic selectivity., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cobalt imidazolate frameworks are classical electrocatalysts for the oxygen evolution reaction (OER) but suffer from the relatively low activity. Here, a non-3d metal modulation strategy is presented for enhancing the OER activity of cobalt imidazolate frameworks. Two isomorphous frameworks [Co 4 (MO 4 )(eim) 6 ] (M=Mo or W, Heim=2-ethylimidazole) having Co(eim) 3 (MO 4 ) units and high water stabilities were designed and synthesized. In different neutral media, the Mo-modulated framework coated on a glassy carbon electrode shows the best OER performances (1 mA cm -2 at an overpotential of 210 mV in CO 2 -saturated 0.5 m KHCO 3 electrolyte and 2/10/22 mA cm -2 at overpotential of 388/490/570 mV in phosphate buffer solution) among non-precious metal catalysts and even outperforms RuO 2 . Spectroscopic measurements and computational simulations revealed that the non-3d metals modulate the electronic structure of Co for optimum reactant/product adsorption and tailor the energy of rate-determining step to a more moderate value., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two-dimensional (2D) materials and ultrathin nanosheets are advantageous for elevating the catalysis performance and elucidating the catalysis mechanism of heterogeneous catalysts, but they are mostly restricted to inorganic or organic materials based on covalent bonds. We report an electrochemical/chemical exfoliation strategy for synthesizing metal-organic 2D materials based on coordination bonds. A catechol functionalized ligand is used as the redox active pillar to construct a pillared-layer framework. When the 3D pillared-layer MOF serves as an electrocatalyst for water oxidation (pH 13), the pillar ligands can be oxidized in situ and removed. The remaining ultrathin (2 nm) nanosheets of the metal-organic layers are an efficient catalyst with overpotentials as low as 211 mV at 10 mA cm -2 and a turnover frequency as high as 30 s -1 at an overpotential of 300 mV., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)