Interzeolite Conversion-Synthesized Sub‑1 μm NaA Zeolite Membrane for C₂H₂/C₂H₄ Selective Separation

Zeolite membranes with reduced thickness and high continuity are of paramount importance for accelerating selective gas separation for resemblant molecules, and the synthesis of such membranes remains a grand challenge. Herein, we developed an interzeolite conversion synthesis approach to grow NaA zeolite membranes on NaX. The conversion of NaX into NaA proceeded via mild hydrothermal treatment of a dilute synthesis solution, preferentially forming a continuous polycrystalline NaA layer on the surface of NaX, which was precrystallized on a porous alumina support. The thickness of the NaA zeolite membrane was successfully controlled to the submicron scale (500 nm). The synthesized NaA membrane functioned as a selective separator for C₂H₂ and C₂H₄ gases. Taking the traditionally in situ grown membrane as a reference, the interzeolite-derived membrane exhibited a 3.5-fold separation factor and ∼4.0 times C₂H₂ permeance. This approach provides an alternative synthesis option for zeolite membranes with advanced properties, and high efficiency in terms of superior gas selectivity and permeability is promising in precise gas separation.