Nanoporous Cu(I) Cluster-Based Covalent Organic Framework for the Chemical Fixation of CO ₂ with C–H Bonds at Atmospheric Conditions

The utilization of CO 2 as a C1 building block for preparing significant chemicals and fuels presents an excellent opportunity to alleviate the growing atmospheric CO 2 concentration. Herein, we demonstrate the application of a two-dimensional (2D), nanoporous metal–covalent organic framework (MCOF) comprising Cu 3 clusters for efficiently transforming CO 2 into two crucial carboxylated compounds, viz., propiolic acids and pyridone-3-carboxylic acids, which are crucial precursors for preparing various antibiotics and drug molecules. The synergistic role of the N-rich triazine scaffold and the high density of Cu(I) catalytic sites in the MCOF promoted high CO 2 uptake and catalytic performance for the carboxylation of sp and sp 2 C–H bonds in phenylacetylenes and 4-hydroxy-2-pyridones with CO 2 to produce the corresponding carboxylated products under ambient conditions. Moreover, the analogous Cu(I)-MCOF′, which lacks basic triazine N sites, exhibits lower CO 2 uptake and catalytic performance. Remarkably, Cu(I)-MCOF exhibited good substrate tolerance in both catalytic transformations, along with excellent recyclability and chemical stability under sustainable reaction conditions. The detailed mechanistic pathway of Cu(I)-MCOF catalyzed CO 2 transformation to propiolic acids and pyridone-3-carboxylic acids has been elucidated by theoretical studies. This work demonstrates the catalytic potential of Cu 3 -trinuclear cluster-based MCOF, which activates CO 2 for carboxylation of relatively inert C–H bonds, delivering important aromatic acids under environmentally benign conditions.