Elimination of Grain Boundary Defects in Zeolitic Imidazolate Framework ZIF‐95 Membrane via Solvent‐Free Secondary Growth.

Metal–organic framework membranes are usually prepared by in situ or secondary growth in a solution/hydrogel. The use of organic solvents may cause safety and environmental problems and produce solvent‐induced defects. Here, highly oriented and permselective ZIF‐95 membranes are prepared for the first time via a solvent‐free secondary growth method. The solvent‐free growth is not only helpful to control the membrane microstructure and thickness, but also to reduce the intercrystalline defects. In case of solvent‐free growth, a perfectly oriented structure leads to an outstanding reduction of intercrystalline defects and transport resistances. For the separation of equimolar binary gas mixtures by using the highly oriented ZIF‐95 membrane at 25 °C and 1 bar, the mixture separation factors of H2/CO2 and H2/CH4 are 184 and 140, respectively, with H2 permeance of over 1.9×10−7 mol m−2 s−1 Pa−1 which are much higher than those of the randomly oriented ZIF‐95 membrane. [ABSTRACT FROM AUTHOR]