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The use of carbon dioxide as a renewable and environmentally friendly source of carbon in organic synthesis is a highly attractive approach, but its real world applications remain a great challenge. The major obstacles for commercialization of most current protocols are their low catalytic performances, harsh reaction conditions, and limited substrate scope. It is important to develop new reactions and new protocols for CO 2 transformations at mild conditions and in cost-efficient ways. Herein, a copper-catalyzed and copper-N-heterocyclic carbene-cocatalyzed transformation of CO 2 to carboxylic acids via C─H bond activation of terminal alkynes with or without base additives is reported. Various propiolic acids were synthesized in good to excellent yields under ambient conditions without consumption of any organometallic or organic reagent additives. This system has a wide scope of substrates and functional group tolerances and provides a powerful tool for the synthesis of highly functionalized propiolic acids. This catalytic system is a simple and economically viable protocol with great potential in practical applications.

An N‐heterocyclic carbene (NHC) polymer supported silver nanoparticle catalyst system was developed. The novel nano‐composite catalyst demonstrated very high activity and excellent stability and reusability in the carboxylation of terminal alkynes with carbon dioxide at ambient conditions. The unique N‐heterocyclic carbene polymer and silver nanoparticle composite structure provided a synergistic effect on activation of terminal alkynes and carbon dioxide that contributed to the high catalytic activity. The poly‐NHC‐silver catalyst exhibited excellent substrate generality and tolerance to various functionalities. In addition, the catalyst is stable to air and moisture and can be easily recovered and reused.