Crystallization-controlled defect minimization of a ZIF-67 membrane for the robust separation of propylene and propane

Abstract

Translating rigid structural ZIF-67 into a highly permselective membrane for the robust separation of C3H6 and C3H8 is desirable but remains challenging. The way to this goal requires the precise control of grain boundary structure to minimize non-intrinsic transport pathways. This study reports a time-saving and reliable rapid thermal conversion strategy to prepare a high-quality ZIF-67 membrane. In this case, the ligand-to-metal ratio determines the quality of the grain boundary structure, which can be rationally modulated to achieve a well-constructed membrane configuration. The resultant ZIF-67 membrane harvested an impressive C3H6/C3H8 selectivity of over 120 and exhibited exceptional thermal stability as well as adaptability to the C3H6/C3H8 feeds with different compositions. Because of the suppressed inter-grain defects, the ZIF-67 membrane delivered improved C3H6/C3H8 separation performance at a feed pressure range of 1–7 bar. Moreover, the membrane demonstrated outstanding long-term durability over a 32-day measurement. By reducing the synthetic solution concentration, the membrane permeance of C3H6 can be significantly increased from 1.0 × 10−8 mol m−2 s−1 Pa−1 to 4.8 × 10−8 mol m−2 s−1 Pa−1 without compromising the selectivity. It made the ZIF-67 membrane one of the top-performing candidates for robust C3H6/C3H8 separation.