Metal-Free Amine-Anchored Triazine-Based Covalent Organic Polymers for Selective CO<sub>2</sub> Adsorption and Conversion to Cyclic Carbonates Under Mild Conditions
Seenu Ravi, Jinwoo Kim, Yujin Choi, Hyug Hee Han, Shiliang Wu, Rui Xiao, Youn‐Sang Bae
Abstract
Attaining both large uptake and high conversion of CO 2 under mild reaction conditions within a metal-free covalent organic polymer (COP) is an attractive and challenging strategy for CO 2 utilization because CO 2 is an abundant and renewable C1 source and a main greenhouse gas. In this study, novel amine-anchored covalent triazine aromatic polymers (CTP-1-NH 2 and CTP-2-NH 2 ) were synthesized from 2-amino-4,6-dichloro-1,3,5-triazine, biphenyl, and 1,3,5-triphenylbenzene via facile Friedel–Crafts arylation for CO 2 adsorption and conversion reaction. At 273 K and 1 bar, CTP-1-NH 2 and CTP-2-NH 2 exhibited CO 2 uptakes of 187.4 and 224.41 mg/g and CO 2 /N 2 selectivity of 69.45 and 61.38, respectively, outperforming many previously reported COP materials. Moreover, metal-free CTP-1-NH 2 with tetrabutylammonium bromide ( n -Bu 4 NBr) exhibited high epoxide conversion and product selectivity under mild (40 °C and 1 bar) and solvent-free conditions within 36 h of reaction time, which were very much comparable to the performances of many metal-coordinated COP catalysts. The spent catalyst was also highly reusable with no active species leaching. A plausible mechanism for CO 2 cycloaddition over the CTP-1-NH 2 catalyst is proposed. Incorporating amine functionalities into a nitrogen-rich structure could be a promising strategy for developing materials with simultaneous CO 2 capture and conversion.