Understanding the Chemical and Electronic Properties of Sub-Monolayer TiO₂ on High Surface Area Silica for Jet Fuel Synthesis Applications

2.5% of global carbon emissions result from air travel, underscoring the need for sustainable aviation fuels (SAF) derived from second-generation lignocellulosic biomass to enhance the green credentials of the aviation sector. This study demonstrates the first solvent-free photocatalytic conversion of furfural (FAL) and cyclopentanone (CPO) to produce 2,5-bis(2-furylmethylidene)cyclopentanone (F2Cp), a jet fuel precursor, using Ti-SBA-15 catalysts, synthesized via alkoxide grafting and controlled titanium surface coverage. Sub-monolayer titania films on SBA-15 supports are achieved with tuneable Ti content, confirmed by XPS (X-ray photoelectron spectroscopy), UPS (ultraviolet photoelectron spectroscopy), REELS (reflectance electron energy loss spectroscopy), ISS (ion scattering spectroscopy), and Raman analysis. XPS analyses reveal coverage-dependent Ti speciation, transitioning from isolated Ti atoms to interconnected Ti-O-Ti networks, with corresponding shifts in Auger parameters, indicating increased surface polarizability and Lewis acidity. Optimized Ti-SBA-15 catalysts exhibit a fourfold activity enhancement in photocatalytic activity over bulk TiO₂, attributed to improved mass transport, active site accessibility, and surface stability. This work highlights the potential of rationally designed hierarchical catalysts for scalable, energy-efficient biomass valorization into SAF precursors, offering a scalable, energy-efficient pathway for sustainable jet fuel production. By elucidating the structure-function relationships in sub-monolayer Ti-SBA-15 materials, this study provides critical insights for advancing photocatalytic technologies in renewable energy applications.