Improved selectivity and anti-aging ability for 6FDA type carbon molecular sieve membranes by mixing silicon from macro-phase separation to molecule doping

•High content of Si molecule doped CMSM was prepared.•Benzimidazole effectively enhanced the compatibility between PI and siloxane-Cl.•Miscible siloxane-Cl evolved into chemical bonding of Si molecule inside CMSM.•Immiscible phase formed the hollow structure with Si-rich interlayer and hole.•Both Si doping could improve the selectivity and anti-aging ability of CMSM.