Sub-Nano Copper Sites on SiO2 with Downshifted d-Band Centers Dominate Non-Radical Selective Oxidation of Benzene to Phenol

Wenwen Lu; Ting Zhang; Rongjian Ding; Yanling Zhai; Xiaoquan Lu

doi:10.1021/acs.nanolett.5c02838

Sub-Nano Copper Sites on SiO₂ with Downshifted d-Band Centers Dominate Non-Radical Selective Oxidation of Benzene to Phenol

Nano Lett. 2025 Jun 25. doi: 10.1021/acs.nanolett.5c02838. Online ahead of print.

Authors

Wenwen Lu¹, Ting Zhang¹, Rongjian Ding¹, Yanling Zhai¹, Xiaoquan Lu^{1

2}

Affiliations

¹ Institute of Molecular Metrology, College of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, P. R. China.
² Key Laboratory of Bioelectrochemistry and Environmental Analysis of Gansu Province, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. China.

PMID: 40558066
DOI: 10.1021/acs.nanolett.5c02838

Abstract

The identification of dominant reactive oxygen species (ROS) in the direct oxidation of benzene with H₂O₂ holds crucial significance for understanding catalytic mechanisms and guiding catalyst design. Herein, we developed a sub-nanoscale Cu cluster supported on SiO₂ (Cu_n/SiO₂) catalyst, which achieved comparable benzene conversion to its nanoparticle counterpart (46.6% vs 55.4%) while exhibiting significantly enhanced phenol selectivity (96.8% vs 88.1%). Systematic studies reveal distinct reaction pathways between the two catalytic systems. In the Cu_n/SiO₂-catalyzed system, benzene oxidation predominantly proceeds through a nonradical pathway mediated by Cu=O* species, while the nanoparticle Cu_p/SiO₂ catalyst follows a free radical mechanism dominated by ^•OH radicals. Density functional theory (DFT) calculations elucidate the sub-nanoscale Cu_n sites in Cu_n/SiO₂ exhibit a downshifted d-band center relative to CuO nanoparticles in Cu_p/SiO₂, which weakens substrate adsorption strength and redirects H₂O₂ dissociation pathways. The fundamental insights gained from this comparative study elucidate structure-activity relationships in copper-based catalytic systems.

Keywords: H2O2 activation; benzene oxidation; d-band center; reactive oxygen species; sub-nano clusters.