Improving the photogeneration and the lifetime of charge carriers associated with light harvesting is among the main challenges facing materials for photocatalysis. We report here the synthesis of mesoporous TiO2 containing a replica of a chiral nematic structure (CNS) as a photocatalyst with improved light harvesting and photogenerated charge carriers under UV illumination. The CNS of cellulose nanocrystal photonic films, obtained by an evaporation-induced self-assembly method, were successfully transferred into an inorganic TiO2 film by sol–gel mineralization of the biotemplate. The stopband of the photonic films was adjusted by controlling the amount of added d-glucose. The improvement of the kinetics of phenol photocatalytic degradation and H2 production and the enhancement of the TiO2 photoconductivity as measured by time-resolved microwave conductivity, compared to mesoporous TiO2, strongly suggest an increase in light harvesting. The CNS microdomains in TiO2 increase the light scattering within the nanostructure and, thus, the absorption factor of TiO2, resulting in higher photoefficiency. This peculiar structure is used for the deposition of gold nanoparticles (AuNPs) inside the mesopores that are left by the mineralization of the biotemplate. AuNPs act as cocatalysts by leveraging highly photogenerated charge carriers for the production of H2. This straightforward method opens up new opportunities, especially for a wide range of materials, where converting photons into energy remains a major challenge.