Electronic interaction between sub-nanometric Ru entity and TiO2 support regulates the hydrogenation chemistry for selective C-O bond cleavage

Selective C-O bond cleavage without ring saturation is the pillar pursuit in the hydrotreating process for lignin valorization/depolymerization since it avoids the consumption of excessive hydrogen. In this work, the sub-nanometric cluster and nanometric particle of Ru were supported on TiO2 for the hydrogenolysis of C-O bond in aromatic ether. The experimental and theoretical results reveal that, in the catalyst of larger Ru nanoparticles, less electron transfer occurs from individual Ru atom to TiO2, making the Ru-related domains retain the nature of bulky Ru for deep hydrogenation. Sub-nanometric Ru cluster shows more intense electron transfer for individual Ru atom, leading to a stronger modification to Ru domain by TiO2. Such electronic hybridization makes Ru gain the catalytic property of TiO2 to attenuate the activation of aromatic ring, inhibiting ring saturation with maintained C-O cleavage activity. This work implies that further decrease of Ru entity size to single-atom level may achieve the complete inhibition of ring saturation.