Mixed-Valence Cu^I/Cu^II-Eu^III Heterometallic Framework for the Synthesis of α-Alkylidene Cyclic Carbonates from Flue...

The preparation of α-alkylidene cyclic carbonates through a cyclization reaction of propargylic alcohols with CO₂ is important in the industrial process. Herein, a novel mixed-valence heterometallic Cu/Eu-based cationic framework, 1-Eu, was successfully synthesized. The material features a unique 14 Å nanocage structure and was effectively employed in the catalytic conversion of propargylic alcohols with CO₂. 1-Eu exhibits remarkable stability in various solvents as well as under acidic and basic conditions, and can maintain the framework stability even in the presence of the strong organic base DBU. Catalytic evaluations demonstrate that 1-Eu can efficiently promote the conversion of propargyl alcohol and CO₂ to α-alkylidene cyclic carbonates under mild conditions. Furthermore, it demonstrates high catalytic activity in the conversion of the biomacromolecule norethindrone with CO₂. Notably, even when low-concentration CO₂ in simulated flue gas is used as the carbon source, 1-Eu remains highly effective in catalyzing the conversion of propargyl alcohol substrates to the corresponding α-alkylidene cyclic carbonate products. The results of the control experiment show that the synergistic catalytic effect between Cu^I/Cu^II and Eu^III plays a crucial role in the activation of CO₂ and propargyl alcohol, thereby facilitating the catalytic reaction.