Mixed‐Matrix Membranes With Layered Fluorine–Cerium Nanosheets for <scp> CO ₂ </scp> / <scp> CH ₄ </scp> Separation

ABSTRACT Versatile layered fluoride‐cerium nanosheets with thickness about 1.60 nm denoted as F‐Ce are fabricated by a convenient and environmentally friendly approach. Then, Pebax‐1657 is used as the polymer matrix and F‐Ce as inorganic fillers to produce mixed‐matrix membranes (MMMs) for gas separation. Versatile functions in enhancing the membrane performances are exhibited by F‐Ce with intrinsic dual channels. On one hand, the abundant mesoporous slits in F‐Ce enhance gas diffusion, constructs high‐speed transport pathways of CO 2 and improve CO 2 permeability; on the other hand, molecular‐sieving d ‐spacing in F‐Ce endows MMMs with prominently preferential CO 2 transport, which favors the increment of CO 2 /CH 4 selectivity. Furthermore, F‐Ce tends to horizontal arrangement and endows the MMMs with preeminent polymer–nanosheet interfacial compatibility, thereby facilitating the superior performance of F‐Ce in MMMs and leading to improvements in both permeability and selectivity. In addition, the F‐Ce exhibits an affinity for CO 2 and constructs “CO 2 ‐philic, CH 4 ‐phobic” regions in MMMs, and the CO 2 ‐philic regions significantly improves CO 2 /CH 4 solubility selectivity and selectivity. The permeability and selectivity of MMMs in humidified state come to maximum values, 1508 Barrer and 37, respectively, at 8 wt% F‐Ce loading, overcoming Robeson Upper Bound (2008). Besides, the mechanical stability of MMMs was investigated.