Two-dimensional graphitic carbon nitride (g-C3N4) nanosheets are ideal candidates for membranes because of their intrinsic in-plane nanopores. However, non-selective defects formed by traditional top-down preparation and the unfavorable re-stacking hinder the application of these nanosheets in gas separation. Herein, we report lamellar g-C3N4 nanosheets as gas separation membranes with a disordered layer-stacking structure based on high quality g-C3N4 nanosheets through bottom-up synthesis. Thanks to fast and highly selective transport through the high-density sieving channels and the interlayer paths, the membranes, superior to state-of-the-art ones, exhibit high H2 permeance of 1.3 × 10-6 mol m-2 s-1 Pa-1 with excellent selectivity for multiple gas mixtures. Notably, these membranes show excellent stability under harsh practice-relevant environments, such as temperature swings, wet atmosphere and long-term operation of more than 200 days. Therefore, such lamellar membranes with high quality g-C3N4 nanosheets hold great promise for gas separation applications.
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