Carbon coated LaFe_0.92Pd_0.08O₃ composites for catalytic transfer hydrogenation: Balance in the ability of substrates adsorption and conversion

Catalytic transfer hydrogenation (CTH) is a green and efficient pathway for selective hydrogenation of unsaturated aldehydes and ketones. However, managing the abilities of solid catalysts to adsorb substrates and to convert them into desired products is a challenging task. Herein, we report the synthesis of carbon coated LaFe_0.92Pd_0.08O₃ composites (LFPO-8@C) for CTH of benzaldehyde (BzH) into benzyl alcohol (BzOH), using isopropanol (IPA) as hydrogen source. The coating with carbon improves the ability to adsorb/transfer reactants from solution to active sites, and the doping of Pd²⁺ at Fe³⁺ site strengthens the ability of LaFeO₃ to convert BzH into BzOH. A balanced point between them (i.e., abilities to adsorb BzH and to convert BzH into BzOH) is obtained at LFPO-8@C, which exhibits a BzOH formation rate of 3.88 mmol·g_cat⁻¹·h⁻¹ at 180 °C for 3 h, which is 1.50 and 2.72 times faster than those of LFPO-8 and LaFeO₃@C. A reaction mechanism is proposed, in which the acidic sites (e.g., Fe⁴⁺, oxygen vacancy) are used for the activation of C=O bond of BzH and O–H bond of IPA, and the basic sites (e.g., lattice oxygen) for the activation of α–H (O–H) bond of IPA.