Our group finely tuned the slit-like pores of carbon molecular sieving membranes (CMSMs) at Ångstrom level by rational manipulations of pyrolysis temperature. CMSMs with the narrow and uniform ultramicropores centered at 6.0 Ångstrom displayed remarkable permeance of n-butaneand separation factor of n-butane/iso-butane. This work has been published in AIChE Journal, 2019, 65, e16749.