Switchable molecular sieving of a capped metal organic framework membrane

Crystalline microporous membranes are promising materials as they have confined functional channels for molecular sieving and adsorption–diffusion. To date, a convenient method to control the permselectivity of a microporous membrane has remained a challenge. Herein, a functional MOF with an azobenzene side group was fabricated into a continuous, defect-free membrane and the surface could be conveniently covered using β-cyclodextrin through adjusting the configuration of azobenzene via vis light. Thus, the resulting β-CD@UiO-68-azo membrane exhibits enhanced ultra-high H2/CO2 permselectivity and the performance can be controlled by reversible adsorption/desorption of capped β-CD.