a Single fuel permeation of the 1-?m-thick g-C3N4 membrane at space temperature and one??bar. The inset displays the gas selectivity for H2 in excess of other gases. b Permeance and separation components of the 1-?m-thick g-C3N4 membranes during the equimolar mixed-gas permeation at home temperature and one??bar. Inset displays the kinetic diameter