Ruthenium-Based Defective MOFs as Heterogeneous Catalysts for the Hydrogenation of Carbon Dioxide to Formate

The hydrogenation of carbon dioxide to formic acid has attracted considerable interest for carbon utilization and hydrogen storage. Metal–organic frameworks (MOFs), featuring open coordination sites and tunable pore structures, offer unique advantages for heterogeneous catalysis. Herein, we report the catalytic performance of a series of defect-engineered Ru-MOF catalysts for the hydrogenation of CO2 to formate. The catalysts were synthesized by partially substituting the organic linker with 3,5-pyridinedicarboxylic acid (PYDC) to introduce controllable defect sites. Among the series, the defective Ru-MOF prepared with an optimal PYDC ratio of 30% used during synthesis (D3-Ru-MOF) exhibits enhanced catalytic performance for CO2 hydrogenation to formate compared with its nondefective counterpart. After hydrogen pretreatment, D3-Ru-MOF achieves a turnover number (TON) of 1258 at 120 °C over 24 h while maintaining good structural stability. A clear structure–activity relationship was observed with catalytic performance dependent on defect density within the framework. This study demonstrates the effectiveness of defect-engineering in Ru-MOFs for improving CO2 hydrogenation performance.