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The schematic illustration shows the influence of triethylamine (TEA) concentration on ZIF-8 formation.

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In this study, zeolitic imidazole framework 8 (ZIF-8) particles of different sizes were synthesized in aqueous media by varying the concentration of base-type additive, triethylamine (TEA). ZIF-8 with particle sizes of ~134 nm and ~288 nm with surface areas of 418.44 m 2 /g and 491.54 m 2 /g were obtained without altering the crystalline structure. Synthesized ZIF-8 was further heat treated at 100°C for a minimum of 12 hours, which lead to enhancement of its phase crystallinity and a surface area of 981.1 m 2 /g was achieved. Mixed matrix membranes (MMMs) were prepared via the dry-wet phase inversion method by dispersing as-synthesized ZIF-8s, heattreated ZIF-8s and commercial ZIF-8 (~493 nm) into polysulfone (PSf) matrix. The thermal stability and mechanical strength of membranes have shown significant improvement by incorporation of ZIF-8s. The MMMs were further subjected to the permeation experiments of CO 2 and CH 4 . Although the majority of MMMs have shown less selectivity than the neat PSf membrane, incorporation of heat-treated ZIF-8 of the smallest size, exhibited CO 2 /CH 4 selectivity of 28.5, which is significantly higher than 19.43 of the neat PSf membrane. Thus, different ZIF-8 treatment protocols and particle sizes affected the MMMs performance significantly.

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