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.