Directly Gel-Thermal Processing of Linker-Mixed Crystal-Glass Composite Membranes for Sorption-Preferential Gas Separation.

Membrane processes are promising for energy-saving industrial applications. However, efficient separation for some valuable gas mixtures with similar characteristics, such as CH/N and O/N, remains extremely challenging. Metal-organic framework (MOF) membranes have been attracting intensive attention for gas sieving, but it is difficult to manufacture MOF membranes in scalability and precisely tune their transport property. In this study, Gel-thermal processing of linker-mixed MOF crystal-glass composite membranes is reported directly, with the mechanism of adjusting metal-linker bond strengths and angles to disrupt long-range periodicity of MOFs and promote glass phase formation, for sharply sorption-preferential gas separation. This strategy can be realized by using a simple, solvent/precursor-less, and cost-effective gel-thermal approach with two steps of gel coating and thermal conversion, thereby constructing crystal-glass composite membranes in a controllable, processable, versatile, and environmentally friendly route. Moreover, the mixed linkers enable preferential gas affinities and the ultramicroporous glasses can eliminate any membrane defects. The membranes exhibit outstanding gas separation performance for the challenging systems of CH/N and O/N, with mixture selectivities up to 9.3 and 9.6, respectively, far exceeding those of polymer, MOF, and mixed-matrix membranes. The study provides an available route for architecting high-performance membranes for gas separations.