Microporous Polymers for Energy Efficient Gas Separations


Katherine Mizrahi Rodriguez


Katherine Mizrahi Rodriguez, & Zachary P. Smith

Author Affiliation: 

Program in Polymers and Soft Matter, Department of Materials Science and Engineering, Massachusetts Institute of Technology


Today, industrial gas separations such as CO2 removal from natural gas rely primarily on energy-intensive or environmentally unfriendly processes. Polymer membranes are a candidate for gas separations due to their low energy costs and mechanical stability, yet polymer performance is constrained by a trade-off between permeability and selectivity (separation efficiency). One path towards improving separation performance and tackling transport limitations is the development of diffusion-selective polymers like polymers of intrinsic microporosity (PIMs). PIMs’ rigidity and inefficient packing yields an interconnected structure with <2nm micropores, high surface areas, and, as a result, high permeability values. In this study, a leading microporous polymer, PIM-1, is used as a platform to study the effect of functionality and packing structure on gas transport performance. After incorporating carboxylic acid (–COOH), amine (–NH2), and tertbutoxyl (tBOC) chemical groups into PIM-1, pure gas transport measurements for industrially relevant gas pairs such as CH4/CO2 are carried out. The direct effects of side-group chemistry on performance and packing are compared for two hydrogen bonding and CO2 sorbing moieties (–COOH and –NH2); while pore blockage is studied using the tBOC protecting group. Additionally, porosity in the protected polymer is renewed through acid or thermal de-protection of the tBOC group, providing a unique handle to understand the impact of solution or thermal processing on polymer packing and, as a result, transport.