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

Although CO 2 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 CO 2 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 CO 2 hydrogenation to formic acid. An unpredictable conversion (TON = 1.11 × 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. Hydrophobic porous polymers can protect the active metal-hydride intermediate, bring highly efficient catalyst for CO 2 hydrogenation to formic acid in water. An higher conversion can be achieved using p-PNP-Ir in aqueous solution.