Phenanthroline-Functionalized Ligand for Constructing CuBr-Modified Zinc-Organic Framework for Cyclization of Propargylic Amines with Flue Gas at Ambient Conditions.

Metal-organic frameworks (MOFs) have attracted extensive attention in catalyzing carbon dioxide (CO2) transformation; however, this remains a challenge to implement in mild conditions. Herein, a diimidazole-functionalized phenanthroline was designed for constructing a novel two-dimensional zinc MOF (Zn-MOF). Subsequently, Zn-MOF was further utilized for constructing CuBr@Zn-MOF by postsynthetic modification through the coordination of CuBr to improve the catalytic activity toward the fixation of CO2. The catalytic data demonstrate that CuBr@Zn-MOF can efficiently catalyze the fixation of CO2 with propargylic amines under mild and green conditions (1 atm, 25 °C, solvent-free), with a TON value reaching up to 3498 and excellent recyclability (ten cycles). The catalytic activity is significantly superior to that of Zn-MOF due to the synergistic activation of the substrate propargylic amine by CuBr@Zn-MOF and DBU. In addition, CuBr@Zn-MOF can be leveraged for catalyzing a gram-scale reaction, affording a 97% yield. Significantly, CuBr@Zn-MOF exhibits robust performance in converting simulated lime kiln gas (30 vol % CO2) into various oxazolidinones, achieving yields ranging from 61% to 93%. It is hoped that this work can shed light on the exploration of functional ligands for architecting noble-metal-free heterometallic MOF catalysts for highly efficient fixation of CO2 under mild conditions.