Double-ligand Fe, Ru catalysts: A novel route for enhanced H 2 production from Formic Acid

Catalytic Ru- or Fe-complexes bearing two ligands L1, L2, where L1 = phosphine and L2 = Schiff-base ligand, present remarkable H 2 production efficiency from Formic Acid (FA) than their single-ligand counterparts. The optimum L1RuL2 and L1FeL2 catalysts were obtained using a phosphine = P(CH 2 CH 2 P Ph 2 ) 3 (or PP 3 ) as L1 and a Schiff-base ligand (abbreviated L γ herein) as L2, while the using of amino functionalized nanoparticle H 2 N@SiO 2 as cocatalyst further promotes the H 2 production efficiency. In long term stability experiments [RuPP 3 L γ ]/H 2 N@SiO 2 and [FePP 3 L γ ]/H 2 N@SiO 2 achieve a total TONs >17,367 and >29,372 respectively without deactivation. Thermodynamic and spectroscopic data reveal a common catalytic mechanism for both Fe and Ru based systems, involving synergism between L1, L2 in order to promote the rate-limiting steps. The present work is the first example of “double-ligand catalyst” concept as a novel route for high-efficiency, HCOOH dehydrogenation catalysts, which can be operative for either noble-metal or earth-abundant metals.