Periodic binary Si:Ti, Si:Al mixed macroporous oxides with ultra-high heteroatom loading: a facile sol-gel approach

Highly ordered macroporous mixed metal oxides were prepared with very high mixed metal ratios using an optimized silicon alkoxide prehydrolysis process. The homogenous solutions completely filled the interstitial voids in polymethylmethacrylate (PMMA) artificial opal templates. Subsequent template removal resulted in highly ordered aluminosilicate and titanosilicate inverse opal pore networks. The optimized process allowed the fabrication of periodic binary metal oxide frameworks with 2:1 Si:Al loadings and 1:1 Si:Ti loadings. The mixed metal oxides did not show any phase segregation during high temperature template removal as evidenced by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and Fourier transform infrared spectroscopy (FT-IR). The as formed macroporous metal oxides demonstrate excellent substrate adherence and mechanical stability and showed refractive index modulation in direct relation to the silicon/heterometal ratio in the precursor sol.