MFI Zeolite Membrane with Surface Mo─O Clusters for Inverse CH ₄ /CO ₂ Separation

Abstract Separation of methane (CH 4 ) and carbon dioxide (CO 2 ) is of significant industrial interest for the utilization of biogas, landfill gas and natural gas. While the state‐of‐the‐art membranes are CO 2 ‐selective, CH 4 ‐selective membranes remain elusive, with potential applications in the recovery and purification of methane‐rich gases such as biogas and landfill gas. Herein, we report a molybdenum‐oxygen (Mo─O) functionalized MFI‐type zeolite membrane for inverse CH 4 /CO 2 gas separation. A pure‐silica MFI‐type zeolite membrane is first seeded grown on an alumina support and subsequently functionalized via facile impregnation and calcination of sodium molybdate. The as‐prepared membrane features uniform pores (0.5 nm) and ultrasmall Mo─O clusters (1.6 nm). The Mo─O/MFI membrane selectively permeates CH 4 over CO 2 , achieving an unprecedented CH 4 /CO 2 separation factor of 11.8 alongside a high CH 4 permeance of 2.1 × 10 −8 mol s −1 m −2 Pa −1 . Experimental measurements and theoretical calculations reveal that CH 4 preferentially adsorbs onto Mo─O clusters via hydrogen bond and diffuses rapidly through MFI zeolite pores. This study represents the first demonstration of porous membranes enabling inverse CH 4 /CO 2 separation and offers guidance for the design of next‐generation CH 4 ‐selective membranes.