AbstractThe low-temperature chemical vapor deposition was used to coat zeolitic imidazolate framework-8 crystals onto the selective layer of polysulfone membrane to obtain a composite membrane. The chemical vapor deposition was performed by a reaction between zinc and 2-Methyl-1H-imidazole vapor at room conditions. The physical and chemical properties of the obtained composite membrane were characterized using material analysis methods. The effects of feed pressure and age of the membranes on CO2 and CH4 permeation were investigated. The results showed that the prevailing cracks were decreased in the composite membrane containing zeolitic imidazolate framework-8 nano-crystals. The molecular sieving effect of zeolitic imidazolate framework-8 caused the increase of the CO2/CH4 selectivity of the composite membrane up to 31%. The age of membranes and the feed pressure made slight drops in CO2 and CH4 permeation and less than 4% enhancement in the ideal CO2/CH4 selectivity. The results showed that the low-temperature and room-pressure chemical vapor deposition is useful for enhancing the CO2/CH4 selectivity of polymeric membranes.