Two-dimensional (2D) materials have emerged as excellent nano-building blocks for high performance membranes. Among them, graphitic carbon nitride (g-C₃N₄) nanosheets possess intrinsic nanopores in plane and CO₂-philic property from the rich amine groups, which are in favor of selective transport of CO₂ molecules. Herein, for the first time, g-C₃N₄ nanosheets with tunable CO₂ adsorption properties and nanostructures were synthesized and incorporated into polyether block amide (Pebax) membrane for CO₂ separation. The g-C₃N₄ nanosheets with variable adsorption properties were produced from two monomers, dicyandiamide and melamine, and the variation of nanostructures was controlled by thermal oxidation etching process. The effects of CO₂-philic and molecular sieving properties of g-C₃N₄ nanosheets on solubility and diffusivity of gas molecules in the as-prepared membranes were systematically investigated. The results demonstrated that the g-C₃N₄ nanosheets produced from dicyandiamide and undergoing 4 h thermal etching (DCN-4 nanosheets) showed the optimal CO₂ sorption and sieving property. The membrane with 0.25 wt% DCN-4 nanosheets exhibited simultaneous enhancement in CO₂ permeance and CO₂/N₂ selectivity compared with pure Pebax membrane. Moreover, the membrane maintained its separation performance during long-term operation test, showing great potential for CO₂ capture.

二维（2D）材料已经成为高性能膜的出色纳米构建模块。其中，石墨碳氮化物（gC ₃ N ₄）纳米片具有丰富的胺基团，具有平面内固有的纳米孔和亲CO _2的特性，有利于CO ₂分子的选择性转运。在此，首次合成具有可调节的CO ₂吸附特性和纳米结构的gC ₃ N ₄纳米片，并引入到聚醚嵌段酰胺（Pebax）膜中进行CO ₂分离。gC ₃ N ₄由双氰胺和三聚氰胺这两种单体制备了具有可变吸附性能的纳米片，并通过热氧化刻蚀工艺控制了纳米结构的变化。系统地研究了gC ₃ N ₄纳米片的CO ₂亲和性和分子筛特性对气体分子在制备的膜中的溶解度和扩散率的影响。结果表明，由双氰胺制得的gC ₃ N ₄纳米片经4 h热蚀刻（DCN-4纳米片）显示出最佳的CO ₂吸附和筛分性能。具有0.25 wt％DCN-4纳米片的膜显示出同时增强的CO ₂渗透性和与纯Pebax膜相比的CO ₂ / N ₂选择性。此外，该膜在长期运行测试中保持了其分离性能，显示出捕获CO _2的巨大潜力。