Bimetallic Hf-Based MOFs with Synergistic Metal Sites for CO₂ Conversion to Cyclic Carbonates and N-formamides

The continuous rise in atmospheric CO₂ levels poses significant threats to global ecosystems and human health, underscoring the urgent need for efficient carbon capture and utilization technologies. Metal-organic frameworks (MOFs) have emerged as promising heterogeneous catalysts for converting CO₂ into value-added chemicals. In this work, we report the one-pot synthesis of three novel bimetallic MOFs (Hf-Cu-MOF, Hf-Co-MOF and Zr-Cu-MOF), constructed from hafnium-oxo (or zirconium-oxo) clusters and 4-pyridinecarboxylic acid ligands. These materials exhibit high structural stability and abundant Lewis acid sites. Among them, Hf-Cu-MOF demonstrated superior CO₂ adsorption capacity and catalytic performance in the cycloaddition of CO₂ with epoxides to form cyclic carbonates, achieving a conversion rate of 96.1%. Moreover, Hf-Cu-MOF also catalyzed the N-formylation of amines with CO₂ and phenylsilane under ambient conditions, affording near-quantitative conversion (98.7%). The outstanding performance is attributed to the synergistic effect of unsaturated metal centers (Hf⁴⁺and Cu ions) and O-H groups, which function as Lewis acid sites and Brønsted acid sites, along with the optimized pore confinement within the framework. Notably, a gram-scale synthesis of Hf-Cu-MOF was successfully achieved, demonstrating robust scalability and consistent performance. This study highlights the potential of Hf-based bimetallic MOFs as efficient and reusable catalysts for sustainable CO₂ conversion, presenting promising prospects for industrial application.