Rational regulating pore structures of covalent organic frameworks for sulfur hexafluoride capture and separation
Sulfur hexafluoride (SF 6 ) 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 SF 6 adsorbents. In terms of imine-linked COFs without further modification, the surface area was found to be a prerequisite for achieving high SF 6 uptakes, and a small pore size at ca. 0.9 nm could effectively strengthen the adsorbate-adsorbent interaction and hence enhance the SF 6 /N 2 selectivity. With a large specific surface area, suitable pore size, and strong covalent bonds, RCOF-1 showed superior SF 6 adsorption capacities up to 4.13 mmol g −1 and large SF 6 /N 2 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 SF 6 capture and separation. This work not only provides a series of high-performance SF 6 adsorbents but also broadens the horizon of applications of the emerging COFs, pointing out their development direction in the field of SF 6 capture and separation.
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