A self-supported aZIF-UC-4 glass membrane for gas separation

Metal-organic framework (MOF) membranes have become promising candidates for gas separation due to their adjustable structure, high separation performance, and environmental friendliness. However, the emergence of grain boundary defects, and interface defects between the support layer and separation layer significantly decrease the gas separation performance of MOF membranes. Herein, a self-supported ZIF (zeolitic imidazolate framework) glass membrane is fabricated, eliminating grain boundary defects and cracks through the molten-liquid phase. The fluorine-based linkers with high electronegativity and polarizability are introduced to enhance agZIF-62(a and g denote amorphous and glass, respectively) interaction of CO2 and CH4. The CO2/N2 and CH4/N2 ideal selectivity of agZIF-UC-4 membrane (fluorine-based, UC-4 named by Cambridge University) reach 36 and 6.2, respectively. In addition, the CO2 and CH4 permeance of the agZIF-UC-4 membrane with an independent separation layer and the non-grain boundary has improved to 4752 and 818 GPU, respectively. Under the mixed gas condition, agZIF-UC-4 membrane exhibits good separation performance, exceeding the 2019 Mckeown upper bond of CO2/N2. Moreover, agZIF-UC-4 membrane has good stability for CO2/N2 and CH4/N2 under continuous operation and variable pressure testing. Hence, the self-supported agZIF-UC-4 membrane is a potential candidate for preparing MOF glass membranes with good gas separation performance.