Advanced strategies in MOF-based mixed matrix membranes for propylene/propane separation: A critical review

Isolation of propane (C3H8) from propylene (C3H6) is essential in petrochemical industries to obtain purified C3H6. The commonly practiced cryogenic distillation for C3H6/C3H8 (C3) separation is associated with high energy demands and costs. In addition, similar physicochemical properties of C3H6 and C3H8 make it difficult for C3 separation with other alternative approaches. However, membrane technology registered great importance owing to its low energy consumption, smaller footprints, high efficiency, etc. Particularly, incorporating inorganic nanomaterials into the polymer matrix termed mixed matrix membranes (MMM) exhibit great potential that could eliminate the unsatisfactory performance of polymeric and inorganic membranes towards industrial use by integrating the strengths of both polymeric and inorganic membranes. Among various fillers, metal-organic frameworks (MOF) were explored as potential fillers due to their intrinsic and tuneable characteristics over other fillers. However, polymer plasticization and inadequate MOF/polymer compatibility results in declining C3 separation performance over time and thus making it unfit for direct industrial application. Various approaches including MOF/polymer selection, MOF engineering, polymer modification, and other novel methods have been proposed to enhance the compatibility and performance of MOF-MMM. Hence, it is essential to review these strategies and therefore the prime objective of this article is especially concentrated on discussing the same. Initially, C3 separation mechanisms through membranes and challenges with conventional membranes are mentioned. Lastly, a conclusive summary and future outlooks are provided to reach the industrial application of MOF-MMM for C3 separation.