Fe oxide nanoparticles/Ti-modified mesoporous silica as a photo-catalyst for efficient and selective cyclohexane conversion with O₂ and solar light

We report a new, environmentally and economically friendly photocatalytic process with unprecedentedly high activity for partial cyclohexane oxidation. Mesoporous silicas containing isolated tetrahedrally coordinated Ti and Fe oxide nanoparticles immobilized on the pore surface were synthesized by reacting SBA-15 with Ti(iv) acetylacetonate and Fe(iii) acetylacetonate successively. A variety of characterizations suggested that the grafted tetrahedrally coordinated Ti species were coupled with Fe oxide nanoparticles via Ti-O-Fe bonds. The SBA-15 photocatalysts showed a high yield (up to sub-mmol) and nearly 100% selectivity for the production of cyclohexanol and cyclohexanone with molecular O₂ under solar light. The unprecedentedly high activity could be explained by the lengthened lifetime of the active Ti species by electron delocalization over Ti-O-Fe bonds and the visible light (λ > 420 nm)-induced activity endowed by Fe oxide nanoparticles coupled to the Ti species.