Reticular syntheses of hydrogen-bonded organic frameworks based on pyrazole tetramers with tunable electrostatic potential for enhanced C2H2/CO2 separation

Abstract

Reticular chemistry has been widely used to predict and design structures of MOFs and COFs, but it still limited in HOFs due to the flexible and fragile nature of hydrogen bonding. Herein, by employing the N-H···N hydrogen-bonding tetramers to connect the pyrazole monomers, we realize the reticular syntheses of three isostructural HOFs (HOF-FJU-45, HOF-FJU-46 and HOF-FJU-47) with tunable pore environments and explore their separation performance toward C2H2/CO2 mixtures. Among these three HOFs, the electrostatic potential of pore surface in HOF-FJU-47a with tetraphenyladamantane core is complementary to C2H2, enabling it to perform better C2H2/CO2 separation performance than HOF-FJU-45a with tetraphenylmethane core and HOF-FJU-46a with tetraphenylsilane core. Dynamic breakthrough experiments also confirm that HOF-FJU-47a can achieve superior C2H2/CO2 separation performance with a balanced C2H2 working capacity (1.98 mmol g−1) and separation factor (5.5) in HOFs materials. The multiple host–guest interactions between C2H2 and the framework of HOF-FJU-47a are further revealed by theoretical calculations.