Localized conversion of ZnO nanorods for fabricating Metal-Organic framework MAF-5 membranes for hydrogen separation

Abstract

For the first time, a homologous metal oxides induced approach was used to fabricate MAF-5 membrane for small molecule separation systems. A continuous and dense MAF-5 membrane was well formed on a porous ceramic substrate by the localized conversion of a thinlayer of ZnO nanorods. The ZnO nanorods layer acting as an intermediate plays a multifunctional role in the formation of the high-quality MAF-5 membrane: (1) modifying the porous substrate to make it more smooth and even; (2) inducing the nucleation and growth of MAF-5 membrane; (3) connecting the MAF-5 membrane and substrate tightly to avoid the membrane peeling off. The as-prepared membrane was characterized by various techniques and proved that the membrane is continuous and high-quality. The excellent gas permeation performance for the MAF-5 membrane was achieved for single gases. The ideal selectivities were as high as 80.2, 87.1 and 105.7 for H2/CO2, H2/N2 and H2/CH4, respectively, which are far higher than their corresponding Knudsen diffusion values. It is therefore believed that the MAF-5 membrane is of potential application in the field of some small-molecular gas separation through a molecular sieving effect.