De novo mechanochemical MOF crystallization within polymers to design compatible mixed-matrix membranes for superior methane separation

Natural gas accounts for more than 20 % of the world’s primary energy supply. However, the upgrading of natural gas, especially the separation of CH 4 and N 2 with similar molecular characteristics, remains challenging. Membrane technology is efficient and energy-saving, but the membrane-based CH 4 /N 2 separation usually shows poor performance and hampered by trade-off issue. We report de novo mechanochemical crystallization of metal-organic frameworks (MOFs) within polymers of intrinsic microporosity to design mixed-matrix membranes (MMMs) for CH 4 /N 2 separation. One-pot ball-milling mechanochemistry at room temperature induces in situ crystallization of MOFs and integration of polymers, thereby constructing highly loaded MMMs with ameliorated filler dispersity and interfacial compatibility. As the fillers, consisted of carboxylate linkers and copper centers, improve preferential gas sorption, gas transport process, and polymer arrangement, the MMMs exhibit substantially enhanced separation capability and antiaging property. For CH 4 /N 2 separation, the CH 4 permeability of MMMs before and after aging for 180 days reaches up to 8120 and 7260 Barrer, respectively, which are one to three orders of magnitude larger than that of conventional membranes, while accompanied by greater selectivity of 6.52 and 7.11. Moreover, this strategy is facile and generally applicable for different MOFs, and the MMMs have thermal, humid, and long-term stabilities and show CO 2 permeability over 33,000 Barrer and CO 2 /N 2 selectivity of 20–25. This study illuminates the practicality of mechanochemistry for hybrid membranes and provides an alternative route for gas purification.