Tuning the Multi-Scale Structure of Mixed-Matrix Membranes for Upgrading CO2 Separation Performances

With virtue of high aspect ratio, high external surface area and tunable surface functionality, burgeoning two-dimensional (2D) materials have been widely applied in to preparing mixed matrix membranes (MMMs) for CO2 separation. A novel Pebax MH 1657-based MMM was fabricated by introducing post-synthetic processed and (3-aminopropyl)-diethoxymethyl silane (APDEMS) functionalized 2D MFI nanosheets (AP-L-MFI) as inorganic fillers to enhance CO2/CH4 separation process. The size of nanosheets was gradually reduced by post-synthetic processing, which can help lower their sedimentation rate and achieve uniform distribution of fillers in the matrix. APDEMS grafted on the surface of nanosheets increased their CO2 adsorption capacity and improved interfacial compatibility with matrix. The MMM containing 5 wt% of AP-L-MFI (AP-L-MFI-5 MMM) exhibited the optimum performance with CO2 permeability of 174.7 Barrer and CO2/CH4 selectivity of 41.1. The as-prepared MMM showed an improvement of 9.8% in CO2 permeability and 50% in CO2/CH4 selectivity compared to the MMM doped by 5 wt% pristine MFI nanosheets (MFI-5 MMM). Moreover, benefiting from the improved filler dispersion and interfacial interaction, the optimal AP-L-MFI-5 MMM gave rise to a 23% higher tensile Young’s modulus and a 74% higher strain at break over MFI-5 MMM.