A Solid-State Transformation of Hydrogen-Bonded Organic Frameworks for Efficient Acetylene Storage and Gas Separation.

Developing robust microporous hydrogen-bonded organic frameworks (HOFs) is crucial for exploring novel physical adsorbents and revealing the structure-property relationship of hydrogen-bonding pairing behaviors. However, it is still challenging to obtain dense and stable hydrogen-bonded frameworks due to the rigidity and spatial resistance of the tectonic centers. Herein, we report a robust microporous HOF (HOF-ZSTU-4) via 4,4',4',4″-([1,1'-biphenyl]-4,4'-diylbis(azanetriyl))tetrabenzoic acid (H4BDATB) with flexible nitrogen nodes composing the tectonic center. Single-crystal X-ray diffraction (SCXRD) analysis shows that the activated framework undergoes a solid-to-solid phase transition because of the torsion of the carboxyl-carboxyl dimer, leading to the switching of the framework from the sql topology to the cds topology (HOF-ZSTU-4a). The single-component gas sorption isotherm reveals that HOF-ZSTU-4a has a C2H2 packing density of 0.54 kg L-1, marking it as the most efficient among reported HOFs. In addition, HOF-ZSTU-4a exhibits promising separation selectivity for several binary gas mixtures, and the dynamic separation performance for C2H2/CO2, CO2/N2, and CH4/N2 is verified by dynamic breakthrough experiments.