Single-Site Ruthenium Pincer Complex Knitted into Porous Organic Polymers for Dehydrogenation of Formic Acid

Abstract

Owing to its capacity for reversible hydrogen storage, formic acid (FA) holds great promise as an alternative energy carrier to conventional fossil fuel systems. Whereas the decomposition of FA to hydrogen (H₂ ) and carbon dioxide (CO₂ ) through homogeneous catalysis is well established, the selective and efficient dehydrogenation of FA by a robust heterogeneous catalyst remains a challenge. A new heterogeneous ruthenium pincer framework with single-atomic sites was prepared in one step by the direct knitting of a phosphorus-nitrogen PN³ P-pincer ruthenium complex in a porous organic polymer. The heterogeneous ruthenium complex efficiently dehydrogenates formic acid in both organic and aqueous media with remarkably enhanced stability. Notably, no detectable CO was generated and a turnover number (TON) of 145 300 was attained in a continuous experiment with no significant decline in catalytic activity (in sharp contrast, a total TON of only 5600 was obtained with the homogeneous analog under the same conditions). The single-atomic sites in the porous framework combined the desirable attributes of high reactivity and selectivity of a homogeneous catalyst with the significantly enhanced catalyst stability and reusability benefits of heterogeneous catalysis.

Keywords: dehydrogenation; formic acid; heterogeneous catalysis; porous organic polymers; single-site catalysts.