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.