Effect of COK-12 mesoporous silica modified with CO2-philic groups on Pebax-based mixed-matrix membranes for CO2/CH4 mixed-gas separation

This work reports the fabrication and characterization of Pebax-based mixed-matrix membranes (MMMs) containing 2.5, 5, 7.5 and 10 wt% of functionalized COK-12 silica particles. The research also evaluates the gas permeation properties of MMMs using a CO2/CH4 (50/50 mol%) gas mixture at 35 degrees C and varying feed pressures. In order to introduce covalent linked CO2-philic chains, the functionalization route of COK-12 silica involves an organic chemistry reaction with poly(ethylene glycol) diglycidyl ether and tin (II) chloride as a catalyst. Analyses by small-angle X-ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and N-2 adsorption-desorption validate the formation and functionalization of COK-12. Incorporating functionalized COK-12 silica influences the thermal and structural properties of MMMs in terms of melting temperature and crystalline structure of the Pebax matrix. Furthermore, MMMs exhibit an increment in CO2 permeability, reaching up to 132 Barrer and CO2/CH4 selectivity 60% higher than the pristine polymeric membrane. Mesoporous COK-12 silica is a potential filler for membranes useful for the separation of CO2 from CH4.