Intermetallic copper-based electride catalyst with high activity for C-H oxidation and cycloaddition of CO2 into epoxides

Abstract

Inorganic electrides have been proved to be efficient hosts for incorporating transition metals, which can effectively act as active sites giving an outstanding catalytic performance. Here, it is demonstrated that a reusable and recyclable (for more than 7 times) copper-based intermetallic electride catalyst (LaCu0.67Si1.33), in which the Cu sites activated by anionic electrons with low-work function are uniformly dispersed in the lattice framework, shows vast potential for the selective C-H oxidation of industrially important hydrocarbons and cycloaddition of CO2 with epoxide. This leads to the production of value-added cyclic carbonates under mild reaction conditions. Importantly, the LaCu0.67Si1.33 catalyst enables much higher turnover frequencies for the C-H oxidation (up to 25 276 h(-1)) and cycloaddition of CO2 into epoxide (up to 800 000 h(-1)), thus exceeding most nonnoble as well as noble metal catalysts. Density functional theory investigations have revealed that the LaCu0.67Si1.33 catalyst is involved in the conversion of N-hydroxyphthalimide (NHPI) into the phthalimido-N-oxyl (PINO), which then triggers selective abstraction of an H atom from ethylbenzene for the generation of a radical susceptible to further oxygenation in the presence of O-2.