Oriented mixed‐matrix metal–organic framework membranes with geometrically engineered rigid lattice for gas separation

Abstract Mixed‐matrix metal–organic frameworks (MMMOF) membranes combine the advantages of polymeric materials and metal–organic frameworks (MOFs) to enhance molecular separations. However, achieving optimal separation performance depends on the characteristics of the MOFs and their subsequent impact on channel accessibility. Herein, we incorporated geometrically engineered rigid lattices of Cu 2 (pzdc) 2 (pyz) nanosheets with optimized orientation in 6FDA‐DAM to maximize the exposure of molecular‐sieving pores. These engineered Cu 2 (pzdc) 2 (pyz) frameworks formed a rigid triangular structure exhibiting 35% higher CO 2 /CH 4 adsorption selectivity than the pristine MOFs. Furthermore, the oriented MMMOF membranes demonstrated a 104% increase in CO 2 /CH 4 selectivity compared to pure polymer membranes, while maintaining a high CO 2 permeability of 2061 Barrer, surpassing the 2018 mixed‐gas upper bound. This work demonstrates that synergistic control of framework rigidity and oriented pore alignment is a powerful strategy to overcome the “trade‐off” between permeability and selectivity, providing new inspiration for the design of high‐performance molecular sieving membranes.