Aromatic Amine-Functionalized Covalent Organic Frameworks (COFs) for CO₂/N₂ Separation

Abstract

CO 2 is a prominent example for an exhaust gas, and it is known for its high impact on global warming. Therefore, carbon capture from CO 2 emissions of industrial processes is increasingly important to halt and prevent the disruptive consequences of global warming. Covalent organic frameworks (COFs) as porous nanomaterials have been shown to selectively adsorb CO 2 in high quantities and with high CO 2 /N 2 selectivity. Interactions with amines are recognized to selectively adsorb CO 2 and help capture it from exhaust emissions. Herein, a novel COF (Me 3 TFB-(NH 2 ) 2 BD), which was not accessible via a direct condensation reaction, was synthetized by dynamic linker exchange starting with Me 3 TFB-BD. Despite the linker exchange, the porosity of the COF was largely maintained, resulting in a high BET surface area of 1624 ± 89 m 2 /g. The CO 2 and N 2 adsorption isotherms at 273 and 295 K were studied to determine the performance in carbon capture at flue gas conditions. Me 3 TFB-(NH 2 ) 2 BD adsorbs 1.12 ± 0.26 and 0.72 ± 0.07 mmol/g of CO 2 at 1 bar and 273 and 295 K, respectively. The COF shows a high CO 2 /N 2 IAST selectivity under flue gas conditions (273 K:83 ± 11, 295 K: 47 ± 11). The interaction of the aromatic amine groups with CO 2 is based on physisorption, which is expected to make the regeneration of the material energy efficient.

Expanding the horizons of covalent organic frameworks: sub-stoichiometric synthesis as an emerging toolkit for functional COFs

“…Postsynthetic introduction of primary amine groups or the presence of unreacted amino or carbonyl groups in imine-linked COFs have been shown to result in functional properties that are otherwise difficult to attain in fully formed networks. [98][99][100][101] In this context, several synthetic strategies, including functional group interconversions, [102][103][104][105] transamination reactions, 106,107 and siteselective [108][109][110][111][112] and regioselective synthesis, 113 have been reported to introduce primary amine groups in 2D COFs.…”

“…118,134 Incorporation of amino or carbonyl groups has been a preferred strategy towards enhancing CO 2 uptake in porous materials, particularly under humid conditions. 107,[135][136][137][138][139][140] Polar functional groups in pores are also capable of forming non-covalent interactions, especially hydrogen bonds with water molecules and provide the opportunity to detect or store moisture. 78,79,[141][142][143][144][145][146][147] For instance, the rst reported substoichiometric COF with free carbonyl groups has been adsorption capacities are ∼1.5 times higher than those of similar COFs without free amino groups.…”

Synthesis and up-to-date applications of 2D microporous g-C3N4 nanomaterials for sustainable development

“…[17][18][19][20][21] Specifically, as shown in the Fig. 1, the main 2D materials are graphene, 22 graphene oxide (GO), 23 boron nitride (BNs), 24 metal organic frameworks (MOFs), 25 covalent organic frameworks (COFs), 26 transition metal carbides and nitrides (MXenes) 6 and g-C 3 N 4 , etc. 27 These materials are playing an increasingly important role in sustainable research.…”

Natural Ellagic Acid-Derived Nanoporous Organic Polymers for CO2 and Organic Dye Adsorption

“…Porous organic polymers (POPs) are an emerging class of lightweight robust nanoporous materials constructed from organic monomers via strong covalent bonds. − The tunable pore structure, designable skeletons, and tailored functionality have offered POPs great potential in diverse applications including adsorption/separation, − catalysis, − sensing, − and energy storage. − Over the past few decades, great efforts have been devoted to exploring new functional organic monomers to construct functional POPs for task-specific applications. − However, the functional organic monomers derived from fossil feedstocks are still few and usually expensive because of the complex synthesis routes. Therefore, the exploration of new organic monomers with high functionality and low cost is still highly desirable in the field of POPs.…”