▎ 摘　　要

Graphene oxide (GO) membranes with two-dimensional (2D) interlaminar channels display fascinating properties in gas separation where the separation efficiency is governed by the size and interlayer interactions of 2D channels. Incorporating intercalators into GO interlayers is recognized as an effective strategy to create appropriate microenvironments for biogas upgrading (remove CO2 from raw biogas, specifically CO2/CH4 separation). Herein, we proposed a strategy of using a kind of nanocage, amino-functionalized polyhedral oligomeric silsesquioxane (POSS-NH2), as versatile intercalator to regulate the channel structure and afford favorable microenvironments for CO2/CH4 separation in GO membranes. The channel size of GO membranes was reduced from 9.1 angstrom to 4.7 angstrom by POSS-NH2 crosslinking, which could elevate the diffusion selectivity of CO2/CH4. The amino groups on POSS-NH2 are able to react with CO2 reversibly, facilitating the transport of CO2. Through synergistically intensifying diffusion selective and facilitated transport mechanisms, the optimized membrane CO2/CH4 selectivity reached 74.5, which is superior to most reported values of 2D membranes. Moreover, we selected another POSS intercalator without amino groups, in order to distinguish the contribution of physical and chemical mechanisms to selectivity. Our study may provide a novel avenue in designing versatile intercalators to construct high-performance 2D membranes.