Heterostructured filler in mixed matrix membranes to coordinate physical and chemical selectivities for enhanced CO2 separation

Mixed matrix membranes (MMMs) hold great promise in overcoming the tradeoff between membrane permeability and selectivity. The rational design of fillers to well coordinate physical and chemical selectivities remains challenging. Here, we explore a heterostructured filler by in-situ growth of ZIF-8 on LDH surface (ZIF-8@LDH), which was then embedded into Pebax to fabricate MMMs for CO 2 /CH 4 separation. The proximity effect of the heterostructured filler endows MMMs with superior gas separation performance compared with the control MMMs containing single filler ZIF-8, LDH and dual fillers (where ZIF-8 and LDH are separately incorporated). On one hand, ZIF-8 and abundant hydroxyl groups on LDH afford favorable affinity toward CO 2 , significantly enhancing the physical selectivity of CO 2 /CH 4 . On the other hand, the oriented distribution of ZIF-8 on LDH elevates CO 2 concentration around LDH and increases the efficiency of CO 2 facilitated transport, leading to remarkably enhanced chemical selectivity. Particularly, the optimum separation performance is achieved for MMMs containing 2 wt% of ZIF-8@LDH with a CO 2 permeability of 1307 Barrer and a CO 2 /CH 4 selectivity of 31.6. The unique attributes of heterostructured filler may be extended to fabricate a variety of MMMs for high performance molecular separations.