Cobalt single atoms anchored on nitrogen-doped porous carbon as an efficient catalyst for oxidation of silanes

Abstract

The oxidation reactions of organic compounds are important transformations for the fine and bulk chemical industry. However, they usually involve the use of noble metal catalysts and suffer from toxic or environmental issues. Here, an efficient, environmentally friendly, and atomically dispersed Co catalyst (Co–N–C) was prepared via a simple, porous MgO template and etching method using 1,10-phenanthroline as C and N sources, and CoCl₂·6H₂O as the metal source. The obtained Co–N–C catalyst exhibits excellent catalytic performance for the oxidation of silanes with 97% isolated yield of organosilanol under mild conditions (room temperature, H₂O as an oxidant, 1.8 h), and good stability with 95% isolated yield after nine consecutive reactions. The turnover frequency (TOF) is as high as 381 h⁻¹, exceeding those of most non-noble metal catalysts and some noble metal catalysts. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), extended X-ray absorption fine structure (EXAFS), and wavelet transform (WT) spectroscopy corroborate the existence of atomically dispersed Co. The coordination numbers of Co affected by the pyrolysis temperature in Co–N–C-700, Co–N–C-800, and Co–N–C-900 are 4.1, 3.6, and 2.2, respectively. Owing to a higher Co–N₃ content, Co–N–C-800 shows more outstanding catalytic performance than Co–N–C-700 and Co–N–C-800. Moreover, density functional theory (DFT) calculations reveal that the Co–N₃ structure exhibits more activity compared with Co–N₄ and Co–N₂, which is because the Co atom in Co–N₃ was bound with both H atom and Si atom, and it induced the longest Si–H bond.