Gas separation performance in ultrathin zeolite membranes by topotactic conversion and induction of nanosheets

Microporous framework materials, particularly in their nanosheet form, are promising building blocks for the construction of continuous molecular-sieving membranes and films, enabling a wide range of applications. However, the limited availability of such microporous nanosheets has restricted their broader use in the construction of microporous membranes. Herein, we introduce a topotactic conversion and induction (TCI) strategy that enables the rapid fabrication of ultrathin, continuous zeolite membranes on commercial substrates from heterogeneous zeolite nanosheets, thereby broadening the applicability of nanosheets in gas separation membranes. The versatility of the TCI route is demonstrated by constructing continuous CHA and MEL zeolite membranes through MFI-to-CHA and MFI-to-MEL conversions. This TCI route has the potential to enhance the fabrication of ultrathin, continuous and nanosheet-based microporous membranes and films for diverse applications. Using this route in an active gel, the all-silica CHA (Si-CHA) membrane exhibits CO₂ permeance of ~8800 GPU and CO₂/CH₄ selectivity exceeding 1000. This separation performance index is substantially higher than previously reported values for CO₂/CH₄ separation. Additionally, the fabricated membranes demonstrate high separation performance among reported membrane configurations for CO₂/N₂ separation. Techno-economic analysis indicates that these membranes could reduce CH₄ decarbonization cost by up to ~87% relative to amine absorption.