Flexible Metal-Organic Frameworks for Light-Switchable CO2 Sorption Using an Auxiliary Ligand Strategy.

We report the synthesis and characterization of two photoactive metal-organic frameworks (MOFs), TCM-14 and TCM-15. The compounds were synthesized by incorporating 4,4'-azopyridine auxiliary ligands into pto-type scaffolds that are composed of dinuclear copper(II) "paddle-wheel"-based secondary building units and flexible, acetylene-extended, tritopic benzoate linkers. Room temperature CO2 sorption of the MOFs was studied, and UV-light irradiation is shown to result in reduced CO2 adsorption under static conditions. TCM-15 reveals a dynamic response leading to an instant desorption of up to 20% of CO2 upon incidence of UV light because of the occurrence of nonperiodic structural changes. Physicochemical and computational density functional theory studies were carried out to gain insight into the mechanism of the interaction of light with the frameworks.

4D printing of MXene hydrogels for high-efficiency pseudocapacitive energy storage.

2D material hydrogels have recently sparked tremendous interest owing to their potential in diverse applications. However, research on the emerging 2D MXene hydrogels is still in its infancy. Herein, we show a universal 4D printing technology for manufacturing MXene hydrogels with customizable geometries, which suits a family of MXenes such as Nb2CTx, Ti3C2Tx, and Mo2Ti2C3Tx. The obtained MXene hydrogels offer 3D porous architectures, large specific surface areas, high electrical conductivities, and satisfying mechanical properties. Consequently, ultrahigh capacitance (3.32 F cm-2 (10 mV s-1) and 233 F g-1 (10 V s-1)) and mass loading/thickness-independent rate capabilities are achieved. The further 4D-printed Ti3C2Tx hydrogel micro-supercapacitors showcase great low-temperature tolerance (down to -20 °C) and deliver high energy and power densities up to 93 µWh cm-2 and 7 mW cm-2, respectively, surpassing most state-of-the-art devices. This work brings new insights into MXene hydrogel manufacturing and expands the range of their potential applications.

A highly augmented, (12,3)-connected Zr-MOF containing hydrated coordination sites for the catalytic transformation of gaseous CO2 to cyclic carbonates.

A porous Zr-based MOF, [Zr6(BTEB)4(µ3-O)4(µ3-OH)4(H2O)4], which contains partially hydrated, 12-connected {Zr6} nodes and extended carboxylate ligands (BTEB3-), was synthesized and physicochemically characterised. The resulting (12,3)-connected, 3D framework adopts an uncommon llj topology with a large, solvent accessible void volume of ca. 79% of the unit cell volume. The porous structure facilitates the uptake of N2 and activated samples give rise to BET surface areas of >1000 m2 g-1. Furthermore, the porosity and accessibility of Lewis acidic Zr(iv) sites promote the catalytic transformation of gaseous CO2 to cyclic carbonates via cycloaddition reactions using epoxide reactants, whereby solvated MOFs exhibit higher catalytic performance than thermally treated samples.

Light-harvesting, 3rd generation RuII/CoII MOF with a large, tubular channel aperture.

A photoactive, hetero-metallic CoII/RuII-based metal-organic framework (MOF) with a large channel aperture, ca. 21 Å, is reported. The photophysical properties of the MOF are derived from the RuII nodes giving rise to emission centred at ca. 620 nm and relatively long triplet 3MLCT lifetimes. In addition to the optical attributes, the 1H-imidazo [4,5-f][1,10]-phenanthroline ligand imparts structural functionality to the MOF which is composed of alternating CoII- and RuII-based nodes of Δ and Λ helicity. The framework maintains its integrity upon activation and shows gas sorption behaviour that is characteristic of mesoporous materials promoting high CO2 sorption capacities and selectivities over N2.

A robust amino-functionalized titanium(iv) based MOF for improved separation of acid gases.

A combination of adsorption, microcalorimetry, infra-red spectroscopy and modeling has been implemented to reveal the potential of the H2S resistant amino-functionalized Ti MOF MIL-125 porous solid for the concomitant elimination of CO2 and H2S from biogas and natural gas.

Separation of CO2-CH4 mixtures in the mesoporous MIL-100(Cr) MOF: experimental and modelling approaches.

Carbon dioxide is the main undesirable compound present in raw natural gas and biogas. Physisorption based adsorption processes such as pressure swing adsorption (PSA) are one of the solutions to selectively adsorb CO(2) from CH(4). Some hybrid crystalline porous materials that belong to the family of metal-organic frameworks (MOFs) show larger CO(2) adsorption capacity compared to the usual industrial adsorbents, such as zeolites and most activated carbons, which makes them potentially promising for such applications. However, their selectivity values have been most often determined using only single gas adsorption measurements combined with simple macroscopic thermodynamic models or by means of molecular simulations based on generic forcefields. The transfer of this systematic approach to all MOFs, whatever their complex physico-chemical features, needs to be considered with caution. In contrast, direct co-adsorption measurements collected on these new materials are still scarce. The aim of this study is to perform a complete analysis of the CO(2)-CH(4) co-adsorption in the mesoporous MIL-100(Cr) MOF (MIL stands for Materials from Institut Lavoisier) by means of a synergic combination of outstanding experimental and modelling tools. This solid has been chosen both for its fundamental interests, given its very large CO(2) adsorption capacities and its complexity with a combination of micropores and mesopores and the existence of unsaturated accessible metal sites. The predictions obtained by means of Grand Canonical Monte Carlo simulations based on generic forcefields as well as macroscopic thermodynamic (IAST, RAST) models will be compared to direct the co-adsorption experimental data (breakthrough curve and volumetric measurements).