Noble-Metal-Free Cu(I)-Catalyzed sp and sp2 C-H Carboxylation to Produce High-Value Compounds via CO2 Fixation under Atmospheric Conditions.

The rise in anthropogenic carbon dioxide (CO2) emissions has significantly accelerated global environmental degradation, necessitating controlled measures to achieve carbon neutrality by utilizing CO2 as a C1 feedstock for the preparation of important commodity products and fuels. Herein, we demonstrate the rational design and preparation of a precious metal-free catalyst (Cu(I)@Zr-MOF) by anchoring Cu(I) ions to functionalized Zr-MOF. Notably, Cu(I)@Zr-MOF exhibited high selectivity for CO2 uptake with a surface area of 1083 m2/g. The high concentration of catalytically active Cu(I) sites present in the 1D channels of Cu(I)@Zr-MOF facilitated the efficient transformation of CO2 into phenylpropiolic acids via the carboxylation of C(sp)-H bonds under mild conditions. Additionally, Cu(I)@Zr-MOF enabled the carboxylation of heterocyclic precursors, such as 4-hydroxy-2-pyridones, with CO2 via C(sp2)-H functionalization, yielding pyridone-3-carboxylic acids, which are valuable biorelevant compounds. Importantly, Cu(I)@Zr-MOF maintained excellent performance over several cycles, preserving both its catalytic efficiency and chemical stability. Furthermore, theoretical calculations elucidated the detailed mechanism of the Cu(I)@Zr-MOF-catalyzed conversion of CO2 into propiolic acids and pyridone-3-carboxylic acids. This study presents a sustainable approach for a Cu(I) metal-based catalyst that effectively utilizes CO2 for the carboxylation of unreactive C(sp)-H and C(sp2)-H bonds, rendering valuable chemicals such as propiolic acids and pyridone-3-carboxylic acids under environmentally friendly conditions.