Ion incorporation into cobalt(II)-organic framework for green and efficient synthesis of oxazolidinones via carbon dioxide fixation.

Developing a green and efficient method for CO2 transformation is crucial for advancing carbon neutrality and effective resource utilization. Among the transformations, carboxylative cyclization of CO2 to produce oxazolidinones is an atom-economical reaction with valuable pharmaceutical applications. However, most catalytic systems often require high temperatures, organic solvents or show low efficiency. Herein, we report a novel anionic framework, {[NH2(CH3)2]2[Co3(L)3(µ3-O)]·0.37DMA }n (1), which can be synthesized on a gram scale and displays excellent stability. As a catalyst, compound 1 enables the carboxylative cyclization of propargylic amines with CO2 at 70 °C for 12 h under ambient pressure, and can be reused up to 10 times while maintaining structural stability. Given the relatively high temperature and extended reaction time required in the 1-catalytic system, Ag+ and Cu2+ ions are incorporated into the framework of compound 1 through cation exchange. The Ag+-incorporated composite 1-Ag(0.05) exhibits high catalytic efficiency under ambient temperature and CO2 pressure within 6 h without using solvent, and can be reused for at least five successive cycles. Control experiments and DFT calculations reveal that the synergistic interaction between Ag+, Co-framework and DBU is the key factor promoting the reaction. To our knowledge, this study provides the first comprehensive investigation into the impact of ion incorporation on the catalytic performance of a Co-based framework in the carboxylative cyclization of propargylic amines with CO2.