New microporous polymers for carbon dioxide selective membranes

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Energy security and climate change are pressing global concerns. In this context, high performance carbon dioxide selective gas separation membranes are required for purification of biogas, natural gas and efficient carbon capture technology. Carbon dioxide removal using a polymer membrane system offers advantages over alternative processes, most notably energy efficiency, as membranes do not require thermal regeneration, a phase change or active moving parts in their operation. For any gas separation membrane, it is desirable to have good selectivity for the desired gas component combined with high permeability (i.e. flux), to minimise the required size of the system. Unfortunately, current highly permeable polymers possess insufficient selectivity and conversely highly selective polymers possess low permeability. Therefore, the goal of enhancing the selectivity of highly permeable polymers, such as Polymers of Intrinsic Microporosity (PIMs), is an important challenge in chemical engineering. We propose an integrated, multi-skilled and multi-national programme of research that will combine molecular modelling, computational simulation of polymer packing, polymer synthesis, gas adsorption and gas permeability studies to develop polymers for use as highly carbon dioxide-selective membranes. PIMs will be prepared with the direct incorporation of benzimidazole and pyrrolone heterocyclic units into the polymer chains. Calculations show that these heterocyclic units possess a high affinity for carbon dioxide. The proposed polymer design conforms to the concept of PIMs, which requires polymers chains that are both rigid and contorted to frustrate space-efficient packing in the solid state. The combined use of molecular modelling and polymer packing simulations to understand gas permeability and, ultimately, predict performance of PIMs as membrane materials will enable the design of further optimised polymers. Achieving the objective of the proposed research programme would be an important first step towards providing carbon dioxide selective membranes of real utility in biogas and natural gas purification, carbon capture and for several niche applications.