Facile hydrogenation of bicarbonate to formate in aqueous medium by highly stable nickel-azatrane complex

Abstract

Molecular catalyst-based direct hydrogenation of bicarbonate to formate in aqueous medium is a challenging research topic for the H2 storage. Finding a green and effective method for the bicarbonate to formate conversion with non-precious metal-based catalyst is vital to the practical application. We report the direct hydrogenation of bicarbonate to formate using a water soluble nickel-azatrane complex. Catalysts 1–5, designed and synthesized, were screened for the hydrogenation of bicarbonate to formate in aqueous medium; the best TON of 121 was obtained for catalyst 4 at 120 °C (60 bar). Introduction of isopropyl (2) and methyl (3 and 4) groups in the coordination environment of the metal center enhances the production of formate. Further, the hydrogenation of bicarbonate with CO2 promoted the formate production for catalyst 4 with a TON of 92 (3 h). The use of green solvent and non-precious metal catalyst makes this catalytic method environmentally sustainable.