Ionic liquid-decorated COF and its covalent composite aerogel for selective CO2 adsorption and catalytic conversion

Abstract

Atmospheric CO₂ is closely related to the greenhouse effect. Therefore, new practical materials and techniques for highly selective CO₂ adsorption and catalytic conversion are imperative. Covalent composites of covalent organic frameworks (COFs) with polymers (oligomers) might be a promising approach to meeting the multifaceted requirements of CO₂ treatment. Herein, a novel COF–chitosan composite aerogel (COF-IL@chitosan) was designed and fabricated by chemical crosslinking of an allyl-imidazolium ionic liquid-decorated COF (COF-IL) with a thiol-attached chitosan (chitosan–SH) binder via a photoinduced thiol–ene reaction. The crystalline structure, highly selective CO₂ adsorption and catalytic conversion features of COF-IL were found to be well maintained in the composite aerogel. The generated covalently coupled COF–chitosan composite material COF-IL@chitosan was found to be robust, uniform and processable even with a remarkably high COF loading (up to 80 wt%). More importantly, the processable COF-IL@chitosan aerogel could be readily shaped into a simplified fixed-bed reactor model via a facile templated freeze-drying procedure, and a scaled-up recyclable CO₂ cycloaddition reaction was realized.