Heterogeneous amino-functionalized particles boost hydrogen production from Formic Acid by a ruthenium complex

Abstract Silica Amino –Functionalized H 2 N@SiO 2 nanoparticles are shown to boost by >700% the TONs of H 2 production by the [Ru/P(CH 2 CH 2 P Ph 2 ) 3 ] homogeneous catalyst, using Formic Acid (FA) as substrate. Thermodynamic analysis reveals that a significant decrease of the activation energy from Ea = 41±9 kJ/mol to Ea = 28±5 kJ/mol occurs when the H 2 N@SiO 2 solid material is used as cocatlasyt vs. the corresponding propylamine in homogeneous phase. The molecular basis of this thermodynamic mechanism was traced using EPR and variable-Temperature UV–Vis spectroscopy. It is shown that H 2 N@SiO 2 particles play a dual role: [i] they act as cocatalyst, and [ii] they serve as a template which assembles the [Ru/P(CH 2 CH 2 P Ph 2 ) 3 ] catalyst on its surface, thus promoting rapid formate decomposition via [Ru II -hydride] species. Moreover we exemplify, for the first time, that the use of heterogenised H 2 N@SiO 2 cocatalyst alleviates the –so far required-need of excess of amines as additives i.e. a ratio [amine (H 2 N@SiO 2 ): Ru complex] = [1:1] is adequate to promote high TONs, instead of [50:1] typically needed for liquid amines.