Hetero-motif POM molecular junctions enable tandem olefin epoxidation and CO2 fixation

Abstract

Olefin epoxidation and CO₂ cycloaddition are important catalytic reactions for the preparation of cyclic carbonates, valuable intermediates in chemical industry. The development of a single heterogeneous catalyst capable of efficiently catalyzing both transformations, however, remains a considerable challenge. Herein, two polyoxotungstate-based copper-organic frameworks, [Cu(1-eIM)₄]₃(VW₅O₁₉)₂·2(1-eIM) (PCF-1) and [Cu(1-iPIM)₄]₃[VW₁₂O₄₀]·(OH)₃ (PCF-2), have been synthesized and structurally characterized. These compounds possess multi-dimensional frameworks with excellent solvent and pH stability, and are covalently assembled through Cu–O–W linkages between polyoxotungstate clusters and imidazole-copper units. Density functional theory calculations reveal that the polyoxometalate (POM) acidic sites are more favorable for styrene adsorption, whereas the Cu sites preferentially interact with CO₂. In catalytic tests, PCF-2 exhibits superior performance in both reactions, giving yields of 88% for olefin epoxidation and 99% for CO₂ cycloaddition, together with excellent recycling stability. This study provides an effective strategy for constructing POM-based heterogeneous molecular junction catalysts for tandem organic transformations.