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Biotemplating technique allows the synthesis of catalysts, recreating the sophisticated structure of nature templates. In this work, some biotemplated TiO 2 semiconductors were synthesized using Olea europaea leaves as templates. Then, g-C 3 N 4 was coupled to materials to later incorporate Pt on the surface or as dopant in the structure to evaluate the efficiency of the solids in two photocatalytic applications to valorize biomass: hydrogen production through glycerol photoreforming, and photoacetalization of cinnamaldehyde with 1,2-propanediol. In glycerol photoreforming, the presence of Pt (superficial or dopant) enhanced hydrogen production, being Pt@AOLCN (a heterojunction containing biotemplated TiO 2 , g-C 3 N 4 , and Pt) the system that exhibited the highest efficiency (3053.4 µmol·g cat -1 ·h -1 ). For photoacetalization, while Pt reduced cinnamaldehyde conversion, it improved selectivity when incorporated on TiO 2 . Notably, carbon nitride (CN) exhibited the highest yield after 16 h of testing. The study emphasizes the importance of tailoring catalyst selection to specific reactions, as efficiency is closely tied to the structural and chemical properties of the materials. These findings contribute to the development of efficient photocatalysts for sustainable biomass valorization processes.

Several biochars were synthesized from olive stones and used as supports for TiO 2 , as an active semiconductor, and Pt as a co-catalyst (Pt/TiO 2 -PyCF and Pt/TiO 2 -AC). A third carbon-supported photocatalyst was prepared from commercial mesoporous carbon (Pt/TiO 2 -MCF). Moreover, a Pt/TiO 2 solid based on Evonik P25 was used as a reference. The biochars used as supports transferred, to a large extent, their physical and chemical properties to the final photocatalysts. The synthesized catalysts were tested for hydrogen production from aqueous glycerol photoreforming. The results indicated that a mesoporous nature and small particle size of the photocatalyst lead to better H 2 production. The analysis of the operational reaction conditions revealed that the H 2 evolution rate was not proportional to the mass of the photocatalyst used, since, at high photocatalyst loading, the hydrogen production decreased because of the light scattering and reflection phenomena that caused a reduction in the light penetration depth. When expressed per gram of TiO 2 , the activity of Pt/TiO 2 -PyCF is almost 4-times higher than that of Pt/TiO 2 (1079 and 273 mmol H 2 /g TiO2 , respectively), which points to the positive effect of an adequate dispersion of a TiO 2 phase on a carbonaceous support, forming a highly dispersed and homogeneously distributed titanium dioxide phase. Throughout a 12 h reaction period, the H 2 production rate progressively decreases, while the CO 2 production rate increases continuously. This behavior is compatible with an initial period when glycerol dehydrogenation to glyceraldehyde and/or dihydroxyacetone and hydrogen predominates, followed by a period in which comparatively slower C-C cleavage reactions begin to occur, thus generating both H 2 and CO 2 ., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Hydrogen production is mainly based on the use of fossil fuels, but currently, many alternative routes are being developed, among which the photo-reforming of oxygenated organic compounds stands out. Recently, several studies have been carried out in order to develop new techniques to create bio-inspired TiO 2 structures. One of these is 'biotemplating', a process that replicates a biological system in an inorganic TiO 2 -based structure. In this study, olive by-products-olive leaves-are valorized as a biotemplate for the synthesis of new Fe-TiO 2- and Cu-TiO 2 -based photocatalysts with the aim of improving the replication of the leaf structure and enhancing hydrogen photoproduction. In conclusion, the incorporation of iron and copper decreases the band gap and increases the energetic disorder at the band edges. Moreover, it is verified by SEM and TEM that the metals are not found forming particles but are introduced into the formed TiO 2 structure. The accuracy of the internal and external structure replication is improved with the incorporation of Fe in the synthesis, while the incorporation of Cu substantially improves the production of hydrogen, which is multiplied 14 times under UV light and 6 times under sunlight, as compared to a pure TiO 2 structure.