Particle-Size Effects on Gas Transport Properties\nof 6FDA-Durene/ZIF-71 Mixed Matrix Membranes

Abstract

A series of 6FDA-Durene-ZIF71\nmixed matrix membranes (MMMs) comprising\nthree different ZIF-71 particle sizes (i.e., 30, 200, and 600 nm)\nhave been fabricated to investigate the effects of particle size on\nthe gas separation performance of MMMs. Compared to MMMs containing\nZIF-71 particle size > 200 nm, ZIF-71 embedded MMMs with particle\nsizes of ≤ 200 nm exhibited significantly enhanced gas separation\nperformance. The O₂ and N₂ permeability of MMMs\ncomprising ZIF-71 with particle sizes ≤ 200 nm have higher\npermeability than the predicted ones using the Maxwell model. By considering\nthe inefficiently packed polymer chain and the sieve-in-a-cage phenomena,\nthe modified Maxwell model displayed comparable permeability over\nthe experimental results suggesting the nonideal nature of MMMs. For\nthe first time, it was found that 200 nm ZIF-71 generated the best\nMMM for gas separation, particularly for H₂/CH₄ systems. Therefore, a trade-off between ZIF-71 particle size vs\ngas separation performance must be taken into account when designing\nan MMM suitable for industrial gas separation applications.