▎ 摘　　要

Interfacial engineering has demonstrated a significant effect on fabricating highly efficient membranes for gas separation. Herein, we introduced a new way to prepare a soft MOF membrane with a modified interface using polyelectrolyte branched polyethyleneimine (PEI) as the joint material. Assembled with layered graphene oxide (GO) and zeolitic imidazolate framework-8 (ZIF-8) nanocrystals, branched PEI not only functions as a soft coat onto the ZIF-8 surface to overcome the rigid nature but also well connects with GO nanosheets via electrostatic attraction, thus preventing the fracture of the membrane. When employed as the gas separation membrane for H-2/CH4, the long gas diffusion pathway determined by layered GO and the accurate sieving effect endowed by ZIF-8 enable the remarkable permeance and selectivity. Furthermore, by simply altering the content of GO nanosheets and ZIF-8 nanocrystals in the composite membrane, one can easily adjust the permeance and selectivity toward the separation of H-2/CH4 gas mixture.