Micrometer-sized MOF particles incorporated mixed-matrix membranes driven by π-π interfacial interactions for improved gas separation

Metal-organic frameworks (MOFs) materials with excellent molecular sieve separation properties are ideal fillers for preparing mixed-matrix membranes (MMMs). Micrometer-sized MOF particles have good dispersion and highly intact crystal structure, thus achieving more efficient gas separation. However, large size MOFs tend to produce more interfacial defects during the membrane forming process. In this work, π-π interactions are constructed at the interface between micrometer-sized ZIF-11 (mZIF-11) particles with diameter of 5-10 μm and polyimide (BIMPI) matrix. The molecular simulation shows that π-π interaction could apparently enhance the interfacial interaction and promote the formation of nearly non-defective interface. mZIF-11/BIMPI MMM with a mass loading of 60 wt% is successfully fabricated and exhibits good mechanical properties. Comparing to the pure BIMPI membrane, the permeability of H2 and CO2 of 50 wt% mZIF-11/BIMPI MMM increases by 492% to 267.6 Barrer and by 410% to 99.0 Barrer, respectively. The H2/CH4 and CO2/CH4 selectivities of the MMM are 164.2 and 60.7 with 56% and 35% increases, respectively, largely exceeding the state-of-the-art Robeson upper bound. In addition, the CO2 plasticization pressure of the mZIF-11/BIMPI MMMs exceeds 40 bar. This work provides an easy and feasible route for constructing MOFs-based MMMs with high mass loading and improved membrane separation performance and stability.