Rational regulating pore structures of covalent organic frameworks for sulfur hexafluoride capture and separation

Abstract

Sulfur hexafluoride (SF6) is the most potent greenhouse gas whose emission is in great need of reduction during industrial processes. Here, a variety of imine-linked covalent organic frameworks with varying surface areas, pore size distributions, and topologies are rationally designed and regulated for systematically studying structure–property relationships of COF-based SF6 adsorbents. In terms of imine-linked COFs without further modification, the surface area was found to be a prerequisite for achieving high SF6 uptakes, and a small pore size at ca. 0.9 nm could effectively strengthen the adsorbate-adsorbent interaction and hence enhance the SF6/N2 selectivity. With a large specific surface area, suitable pore size, and strong covalent bonds, RCOF-1 showed superior SF6 adsorption capacities up to 4.13 mmol g−1 and large SF6/N2 selectivity up to 125 (273 K, 100 kPa) accompanied by excellent stability, which can be considered one of the most high-performance porous materials for SF6 capture and separation. This work not only provides a series of high-performance SF6 adsorbents but also broadens the horizon of applications of the emerging COFs, pointing out their development direction in the field of SF6 capture and separation.