In situ conversion of ZnO anchored on porous carbon foams to antiflexible ZIF-8-X (X = Co or NH2) for sieving linear and mono-branched hexane isomers

Abstract

Efficient separation of linear hexane from their isomers is a vital petrochemical process to produce high-quality gasoline. Zeolitic imidazolate frameworks-8 (ZIF-8), one of the most famous metal-organic frameworks (MOFs), is a promising separation material due to its special pore size (3.4 Å), whereas the flexible framework limited its separation ability, showing unsatisfied trade-off between adsorption capacity and separation selectivity. Here, we propose a novel strategy of post metal-oxide modification (PMOM) to suppress ZIF-8 flexibility by in situ growth on rigid layer of porous carbon foam (PCF) based the intermediation of anchored ZnO nanoparticles directly obtained from the pyrolysis of sucrose and zinc nitrate mixture. Afterwards, synergistic flexible suppression technology (SFST) was adopted to design antiflexible PCF/ZIFs with mixed-metal and mixed-ligand, including bi-metal PCF/ZIF-8-Co and di-ligand PCF/ZIF-8-NH2. Therein, the tight interfaces generated with benzene-ring inhabited the swinging of linkers and hindered 3-MP entry into the pore channels, showing both remarkable nHex adsorption capacity (q = 2.26 mmol·g−1) and nHex/3-MP selectivity (Su = 9.42). Moreover, bi-component adsorption experiments confirm the practical separation performance and cycling stability, showing promising application in adsorptive separation processes.