Preparation of High‐Strength and High‐Permeability EC/PI/MOF Mixed Matrix Membrane**

Abstract Gas separation technology is one of the difficulties in the chemistry and purification industry. To help solve this problem, we have prepared mixed matrix membranes containing Zr‐based metal‐organic framework (MOF), ethyl cellulose (EC) and polyimide (PI), and characterized them by FTIR, SEM and gas separation measures. The obtained mixed matrix membranes have good mechanical and thermal properties, the tensile strength of mixed matrix membranes improved by 5.44‐10.5 times compared to pure EC membrane. Especially, the mixed matrix membranes exhibited excellent CO 2 permeability compared to pure EC and pure PI membranes. CO 2 permeability of mixed matrix membrane contained 15 % MOF was 145.5 Barrer and the CO 2 /CH 4 permselectivity was 11.95, which increased 2.21 times and 0.45 times compared to pure EC membrane. Comparison with 1991 and 2008 Robeson Upper Bound, the mixed matrix membranes were closer to the Robeson Upper Bound than pure EC membrane.