According to the definition of the International Union of

Modern, highly efficient catalysts are made of materials that usually have high surface areas with nanometric sized particles, normally below 100 nm [28] and [29]. Recent in-depth analyses have shown that the size, shape, and porosity of the particles are the key morphological parameters that can influence their photoactivity. Therefore, a decrease in the particle size of a uniformly dispersed active phase on a highly-ordered porous support material would provide a high surface area photocatalyst and this would generally have a beneficial effect on photoactivity [1] and [28]. Therefore, particular attention has been paid in this study to obtaining nanosized TiO2 dispersed on 3D ordered porous KIT-6 GSK2636771 material, in order to enhance CO2 conversion to fuel and other useful energy-bearing products. The physical characteristics of these synthesized photocatalysts have been obtained by means of N2-sorption, and are summarized in Table 1. KIT-6 has a high surface area (SBET), pore volume (PV), and confined 3D average pore diameter (APD), which are shown in Table 1. As the TiO2 loading was increased, a gradual decrease was observed in the SBET and PV of the KIT-6 support material. This decrease was due to partial surface coverage and blockage by the dispersed TiO2. However, because of the 3D pore structure of KIT-6, a uniform APD was observed in all the catalysts (calcined at 400 °C for 3 h), which did not change significantly. The 3D pore structure was able to accommodate dispersed TiO2 and facilitate an easier and faster diffusion of the reactants and products [25]. Therefore, the TiO2 loadings on KIT-6 were uniform up to 20–30%, while loadings above this decreased the physical characteristics significantly. Different temperature calcination treatments of TiO2(20%)/KIT-6 (ranging 400–800 °C) also showed a decrease in SBET and PV, which might have been caused by the rapid growth of TiO2 due to sintering, and in particular inside the KIT-6 pores.