Post‐Synthetic Covalent Grafting of Amines to NH ₂ ‐MOF for Post‐Combustion Carbon Capture

Abstract Herein, a post‐synthetic modification strategy is used to covalently graft polyamines, including ethylenediamine (ED), diethylenetriamine (DETA), tris(2‐aminoethyl)amine (TAEA), and polyethyleneimine (PEI) to the amino‐ligand inside of a Cr‐MOF, NH 2 ‐Cr‐BDC, for post‐combustion carbon capture applications. X‐ray absorption spectroscopy (XAS), X‐ray photoelectron spectroscopy (XPS), and ion chromatography (IC) reveal that ≈45% of the MOF ligands are grafted with polyamines. Next, assessment of CO 2 uptake, CO 2 /N 2 selectivity, isosteric heats of CO 2 adsorption, separation performance during humid CO 2 /N 2 (15/85) breakthrough experiments, and cyclability, reveals an enhanced performance for the polyamine‐containing composites and the following performance trend: NH 2 ‐Cr‐BDC<ED<DETA<TAEA<PEI. The best‐performing materials, including the TAEA and PEI‐grafted MOFs, offer CO 2 uptakes of 1.0 and 1.55 mmol g −1 , respectively, at 0.15 bar and 313 K. Further, these composites also offer a high CO 2 capacity after 200 temperature swing adsorption/desorption (TSA) cycles in simulated humid flue gas. Last, after soaking the composites in water, there is no loss of CO 2 capacity; on the contrary, when the same MOF is impregnated with polyamines using traditional approaches, there is ≈85% CO 2 capacity loss after soaking. Thus, this covalent grafting strategy successfully immobilizes amines in MOF pores preventing leaching and hence can be an effective strategy to extend the adsorbent lifetime.

Hali tarjima qilinmagan