Coexistence of Cu(II) and Cu(I) in Cu ion doped zeolitic imidazolate frameworks (ZIF-8) for dehydrogenative coupling of silanes with alcohols
Metal-ion-doped zeolitic imidazolate frameworks have got much attention for their structure tailorability and potential catalytic application. Herein, Cu ion doped ZIF-8 nanocrystals were successfully prepared by mechanical grinding of Cu(NO3)2, ZnO and 2-methylimidazole (HMeIM) with ethanol as an additive. Unlike the general view that only Cu(II) was present in Cu-doped ZIF-8, we found the coexistence of Cu(II) and Cu(I) in this material, which was supported by XPS and X-ray induced Auger electron spectroscopy (XAES) characterization. And ethanol may act as a reducer to induce the reduction of Cu(II) during synthesis. As the mixture valence of Cu ions, Cu ion doped ZIF-8 nanocrystals showed excellent catalytic performance for dehydrogenative coupling of silanes with alcohols.