Controlled Secondary Growth of CAU-1-NH ₂ Membranes with Improved CO ₂ Separation Performance

High Resolution Image Download MS PowerPoint Slide Metal–organic framework (MOF) membranes have attracted increasing interest for energy-efficient gas separation due to their tunable pore structures and selective adsorption properties. In this study, CAU-1-NH 2 membranes were fabricated on porous α-alumina substrates via a seeded growth method. The effects of precursor concentration and ligand-to-metal ratio in the secondary growth solution on membrane morphology and gas separation performance were systematically investigated. Among the five membrane variants synthesized, the optimized CAU-1-NH 2 (B) membrane exhibited a continuous and low-defect structure, as confirmed by scanning electron microscopy and confocal fluorescence microscopy. Single-gas permeation measurements on the CAU-1-NH 2 (B) membrane at 35 °C and 3 bar showed H 2, CO 2, N 2, and CH 4 permeances of 207.1, 110.2, 6.0, and 6.6 GPU, respectively, corresponding to ideal CO 2 /N 2 and CO 2 /CH 4 selectivities of 19.4 and 17.6. Mixed-gas permeation tests revealed significantly enhanced separation performance, with CO 2 /N 2 separation factors ranging from 59.3 to 89.2 under various feed compositions. Grand canonical Monte Carlo (GCMC) simulations further indicate that strong competitive adsorption of CO 2 within the CAU-1-NH 2 framework plays a dominant role in governing the observed mixed-gas separation behavior. These findings demonstrate the potential of CAU-1-NH 2 membranes for efficient CO 2 separation.