Simultaneously Enhanced Permeability and Selectivity of Pebax-1074-Based Mixed-Matrix Membrane for CO2 Separation

Membrane technology is a promising methodology for carbon dioxide separation due to its benefit of a small carbon footprint. However, the trade-off relationship between gas permeability and selectivity is one obstacle to limiting its application. Herein, branched polyethyleneimine (BPEI) containing a rich amino group was successfully grafted on the surface of the metal–organic framework (MOF) of AIFFIVE-1-Ni (KAUST-8) through coordination between N in BPEI and open metal sites in the MOF and with the resultant maintained BET surface area and pore volume. Both the strengthened CO 2 solubility coefficients coming from the additional CO 2 adsorption sites of amino groups in BPEI and the reinforced CO 2 diffusivity coefficients originating from the fast transport channels created by KAUST-8 led to the promising CO 2 separation performance for KAUST-8@BPEI/Pebax-1074 MMM. With 5 wt.% KAUST-8@BPEI loading, the MMM showed the CO 2 permeability of 156.5 Barrer and CO 2 /N 2 selectivity of 16.1, while the KAUST-8-incorporated MMM (5 wt.% loading) only exhibited the CO 2 permeability of 86.9 Barrer and CO 2 /N 2 selectivity of 13.0. Such enhancement is superior to most of the reported Pebax-1074-based MMMs for CO 2 separation indicating a wide application for the coordination method for MOF fillers with open metal sites.