Matrimid Mixed Matrix Hollow Fiber Membranes: Influence of ZIF-8 Filler over O₂/N₂ Separation Performance

Oxygen and nitrogen are two valuable and widely used products in industries, medical applications, and the food sector, for instance, so they present a significant market opportunity. Traditional methods to separate these gases are very energy-intensive. Therefore, in a world moving toward energy sustainability, membrane technology offers a more sustainable alternative. The aim of this work is to develop polymeric membranes with a hollow fiber configuration using Matrimid and ZIF-8 as fillers to improve the separation performance. As a first step, planar membranes with varying ZIF-8 content (0-20 wt %) were prepared using the casting solvent evaporation technique to determine the optimal Matrimid/ZIF-8 ratio. Subsequently, hollow fiber membranes of Matrimid and Matrimid/ZIF-8 were fabricated via the spinning method. The novelty of this work lies in incorporating ZIF-8 into Matrimid membranes in a hollow fiber configuration, as it is known that the inclusion of fillers in polymeric membranes allows improvements in their performance. Nevertheless, their production is quite challenging. The flat-sheet membranes prepared have shown that inclusion of ZIF-8 in Matrimid improves its O₂/N₂ selectivity by one point and that 5 wt % loading is the optimal point to see this enhancement. The same effect was observed in hollow fiber membranes, reaching an oxygen permeance of 2.16 GPU and an O₂/N₂ selectivity of around 6 (30 °C) for the Matrimid/ZIF-8 membrane, with a dense layer thickness of around 2 μm. All of these results were compared with those reported in the literature for the O₂/N₂ separation. Additionally, the impact of feed composition variations on membrane performance was analyzed.