Discovery of mono(u-oxo)dicopper and bis(u-oxo)dicopper in ordered Cu incorporated in SBA-15 via sol-gel process from silatrane at room temperature: An in situ XAS investigation

We proposed a synthesis pathway to obtain high-yielding SBA-15 containing copper (Cu-SBA-15) via a sol-gel process from silatrane and discovered that the active copper species had a large pore size and narrow size distribution, where the pore sizes increased with increasing copper content. In addition, the results from UV–Vis–NIR spectroscopy revealed that the active copper species were mono(u-oxo)dicopper [Cu2(μ-OH)2]2+ (21 740 cm−1) and bis(μ- η2: η2 peroxo)dicopper [Cu2(μ- η2: η2-O2]2+ bent (17 850–18 691 cm−1) and planar (24 690 cm−1). Furthermore, the microscopic techniques (scanning (SEM) and transmission (TEM) electron microscopy) showed the characteristic of a long length channel and retained SBA-15 structure after incorporation of Cu, even at high copper loadings, and had a higher copper content loading with a longer length of Cu-SBA-15. In addition, the 9% Cu-SBA-15 was characterized by broad X-ray powder diffraction (XRD) which was used to inspect the aggregation and formation of CuO and no peak was observed. All evidence suggested that the Cu-SBA-15 successfully prepared and discovered the active copper species. In-situ XAS showed that to produce active copper species in Cu-SBA-15, heating under a helium atmosphere at 350 °C for 30 min was sufficient for the formation of bridge oxygen (Cu-Ox-Cu) with the characteristics of mono(u-oxo)dicopper and bis(u-oxo)dicopper.