Aromatic Amine-Functionalized\nCovalent Organic Frameworks\n(COFs) for CO₂/N₂ Separation

Abstract

CO₂ is a prominent example for an exhaust\ngas, and it\nis known for its high impact on global warming. Therefore, carbon\ncapture from CO₂ emissions of industrial processes is increasingly\nimportant to halt and prevent the disruptive consequences of global\nwarming. Covalent organic frameworks (COFs) as porous nanomaterials\nhave been shown to selectively adsorb CO₂ in high quantities\nand with high CO₂/N₂ selectivity. Interactions\nwith amines are recognized to selectively adsorb CO₂ and\nhelp capture it from exhaust emissions. Herein, a novel COF (Me₃TFB-(NH₂)₂BD), which was not accessible\nvia a direct condensation reaction, was synthetized by dynamic linker\nexchange starting with Me₃TFB-BD. Despite the linker exchange,\nthe porosity of the COF was largely maintained, resulting in a high\nBET surface area of 1624 ± 89 m²/g. The CO₂ and N₂ adsorption isotherms at 273 and 295 K were studied\nto determine the performance in carbon capture at flue gas conditions.\nMe₃TFB-(NH₂)₂BD adsorbs 1.12 ±\n0.26 and 0.72 ± 0.07 mmol/g of CO₂ at 1 bar and 273\nand 295 K, respectively. The COF shows a high CO₂/N₂ IAST selectivity under flue gas conditions (273 K:83 ±\n11, 295 K: 47 ± 11). The interaction of the aromatic amine groups\nwith CO₂ is based on physisorption, which is expected to\nmake the regeneration of the material energy efficient.