Controlled Superacid-Catalyzed Self-Cross-Linked Polymer of Intrinsic Microporosity for High-Performance CO<sub>2</sub> Separation
Shengyang Zhou, Yuxuan Sun, Boxin Xue, Shenghai Li, Jifu Zheng, Suobo Zhang
Abstract
Polymers of intrinsic microporosity (PIMs) with superhigh permeability have been widely studied for higher selectivity in the various separation processes. However, the disorder and wide-distribution of pore size limit their molecule selectivity. In this work, at low temperature (60 °C), we design and prepare a superacid-induced self-cross-linked PIM-1 membrane with a rebuilt microstructure by swelling and catalysis of the superacid to achieve fast and accurate gas transport. For PIM-1 membranes, the polymer chains can be activated by CF3SO3H solvation to possess enhanced motion and reactivity. Then, the partial swelled porosities can be solidified with cross-linking of nitrile groups and further be interconnected by narrow channels to form alternating gas pathways, which was supported by X-ray diffraction and small-angle X-ray scattering. As a result, these cross-linked membranes maintain high gas permeability, even approaching to that of pristine PIM-1, and meanwhile exhibit excellent molecular sieving ability, such as CO2/N2 permeation selectivity increasing from 20.4 to 58.1. This indicates that superacid-catalyzed self-cross-linking can effectively adjust the topological structure of PIM-1 for microstructure-dependent applications including but not limited to CO2 separation and fuel cells.