The activation of molecular oxygen (O2) is extremely crucial in heterogeneous oxidations for various industrial applications. Here, a charge-transfer complex CuTCNQ nanowire (CuTCNQ NW) array grown on the copper foam was first reported to show CO catalytic oxidation activity at a temperature below 200 °C with the activated O2 as an oxidant. The molecular O2 was energetically activated over the Cu(I)-mediated C≡N bond with a lower energy of -1.167 eV and preferentially reduced to •O2- through one-electron transfer during the activation process by density functional theory calculations and electron paramagnetic resonance. The theoretical calculations indicated that the CO molecule was oxidized by the activated O2 on the CuTCNQ NW surface via the Eley-Rideal mechanism, which had been further confirmed by in situ diffuse reflectance infrared Fourier transform spectra. These results indicated that the local C≡N bond electron-state engineering could effectively improve the molecular O2 activation efficiency, which facilitates the low-temperature CO catalytic oxidation. The findings reported here enhance our understanding on the molecular oxygen activation pathway over metal-organic nanocatalysts and provide a new avenue for rational design of novel low-cost, organic-based heterogeneous catalysts.
Keywords: CO oxidation; CuTCNQ NWs; DFT calculations; in situ DRIFTS; molecular O2 activation.