Fluorinated Covalent Organic Framework Membranes Enable High‐Efficiency and Water‐Resistance CO<sub>2</sub>/N<sub>2</sub> Separation
Pinyue Zhang, Chi Zhang, Changyan Zhu, Junchao Dong, Hao Zhang, Tianci Shao, Dan Ma, Yuyang Tian, Xiaoqin Zou
Abstract
Abstract Membrane separation is advantageous in mitigating excessive carbon dioxide (CO 2 ) emission of worldwide concern. However, most membranes are vulnerable to water during CO 2 separation from combustion disposal gas, resulting in performance deterioration. Water‐resistant covalent organic framework (COF) membranes for efficient CO 2 separation from wet gas stream are designed and synthesized. Two COFs termed as COF‐TpPa‐1‐CF 3 and COF‐TFBPa‐CF 3 are constructed using planar trifluoromethyl‐functionalized monomers; featuring open straight pores, high hydrophobicity, and unique CO 2 affinity. Liquid–liquid interfacial polymerization renders the self‐standing COF membranes free of cracks. COF‐TFBPa‐CF 3 and COF‐TpPa‐1‐CF 3 membranes are able to separate CO 2 from N 2 under dry and wet conditions; and the former membrane is more resistant against water than the latter one, demonstrated by invariant gas permeation. The COF‐TFBPa‐CF 3 membrane exhibits exceptional CO 2 permeability (>9000 Barrer) and high CO 2 /N 2 selectivity (>25), superior to other reported COF membranes. Moreover, the selectivity‐permeability product breaks 2008 upper bound. The excellent separation performance, water stability, and high reproducibility promise COF‐TFBPa‐CF 3 membrane in practical CO 2 separation from post‐combustion gas.