Disentangling the\nCatalytic Mechanisms of C<sub>60</sub>-Buffered Cu/SiO<sub>2</sub> Catalyst for DMO-to-EG Conversion

Both ethylene glycol and methyl glycolate,\nwhich can\nbe synthesized\nby hydrogenating dimethyl oxalate, are important chemical feedstocks,\nand understanding the mechanistic details underlying those hydrogenation\nreactions is of pivotal importance for the design of high-performance\ncatalysts. In this work, we employ carefully constructed model cluster\ncatalysts, including Cu<sub>4</sub>, C<sub>60</sub>Cu, C<sub>60</sub>Cu<sub>3</sub>, and C<sub>60</sub>Cu<sub>4</sub>, to mimic the widely\nutilized Cu/SiO<sub>2</sub> catalyst and the recently discovered C<sub>60</sub>-buffered Cu/SiO<sub>2</sub> catalyst based on joint efforts\nfrom mass spectrometry, photoelectron spectroscopy, density functional\ntheory calculations, and molecular dynamics simulations. We explored\nthe catalytic mechanisms of the hydrogenation of dimethyl oxalate\ncatalyzed by our model cluster catalysts and uncovered the possibility\nto tune the product selectively by changing the copper cluster size.\nOur results reveal important geometric and electronic effects of C<sub>60</sub> in promoting the catalytic reactions by reversibly accepting\nand donating, i.e., serving as an electron buffer, electrons to the\nadsorbed copper, resulting in the alternating formation of Cu<sup>0</sup> and Cu<sup>δ+</sup> sites in different steps of the\nhydrogenation reactions. These oxidation state changes are crucial\nfor the hydrogenation and stabilization of the reaction intermediates.