Highly efficient catalysts for CO₂ hydrogenation to formic acid in water catalyzed by hydrophobic porous polymers containing stable metal-hydride

Although CO2 hydrogenation to formic acid has been widely investigated, the design of highly stable and effective heterogeneous catalysts is a long-standing challenge due to the instability of the active intermediate in water. Herein, both theoretical and experimental results revealed that the active Ir-H species appearing in the CO2 hydrogenation process can be easily hydrolyzed, resulting in the deactivation of the catalyst. Further research constructed a strategy to protect the active Ir-H species by utilizing a directly-knitted PNP-based catalyst (p-PNP-Ir) for CO2 hydrogenation to formic acid. An unpredictable conversion (TON = 1.11 x 10(6)) can be achieved using p-PNP-Ir in water, being 3.15 times higher than that using the monomer PNP-Ir. Besides, the solid catalysts can be easily recycled for at least 15 runs without activity loss, highlighting their potential for practical applications in industry.