Extended Data Fig. 8: In situ XANES and EPR spectra during C–O coupling reaction.
a,b, In situ Cu K-edge XANES (a) and Fourier-transformed EXAFS (b) spectra of Cug/PCN catalyst measured before and in the C–O coupling reaction, respectively. c, In situ EPR spectra of Cug/PCN recorded at different times in the C–O coupling reaction. The chemical state change of Cug/PCN during the C–O cross-coupling reaction cycle was clearly seen from Cu K-edge XANES. A distinct weakening of the feature peak at 8,983 eV and an increase of the main peak at 8,996 eV indicate that the valence state of Cu increases during the reaction, which is related to the successful adsorption of 4-iodotoluene or methanol. Correspondingly, the intensity of the main peak related to the first coordination sphere in the Fourier-transformed EXAFS spectra increases, evidencing the increased coordination number of Cu. The change in the chemical valence state of Cu during the reaction cycle is further explained by in situ EPR spectroscopy. EPR-silent Cu(I) is first oxidized to EPR-sensitive Cu(II) with a gradually enhanced signal intensity and then reduced to the original Cu(I) state during a complete reaction process, in line with the in situ XAFS results.
