Sub-nano porous graphene-based membranes enabled by in-situ-grown ZIF-8 for enhanced CO2 capture

Graphene oxide (GO) membranes hold promise for selective CO 2 adsorption over N 2 due to their carboxyl groups, making them attractive for flue gas CO 2 capture. However, challenges such as limited carboxyl content, flexible nanosheets, and dense layer stacking hinder their N 2 /CO 2 gas selectivity, pressure resistance, and permeability. In this study, we introduce a specific sub-nanometer framework structure within GO membranes by in-situ growing ZIF-8 nanocrystals. This novel approach, achieved through simultaneous infiltration of zinc nitrate and 2-methylimidazole precursors on both sides of the membrane, enhances CO 2 capture and pressure resistance capabilities of resulting ZIF-8@GO composite membranes. Additionally, the incorporation of carboxylated wrinkled graphene (WG) and ethylenediamine (EDA) cross-linking agent molecules improves CO 2 capture capability and introduces reinforced porous structures to enhance permeability. Experimental results demonstrate remarkable permeability, selectivity, and pressure resistance of the prepared ZIF-8@EDA-GO/WG composite membranes. Under a gas pressure of 0.2 MPa, permeability reaches 1850 GPU, with theoretical selectivity for N 2 /CO 2 single gas and separation factors for mixed gases of 18.3 and 32.3, respectively, surpassing conventional GO membranes (3 GPU, 1.1, and 1.2). Even under elevated air pressure conditions (1.2 MPa), the composite membranes maintain a theoretical selectivity of 13.4. Our CO 2 capture membrane design strategy not only advances the development of functional membranes but also contributes to mitigating CO 2 emissions from flue gas, thereby combating global warming.