Since 1-octanol represents a readily available electron donor with possibly valuable products of its oxidation, the organic phase after 96 h of irradiation of 1-octanol/0.5 M HCl mixture in presence of various photocatalysts was analysed by gas chromatography with a flame ionization detector (GC-FID) (Supplementary Information, Figure ). 1-octanal, octanoic (caprylic) acid and octyloctanoate, whose formation is promoted in presence of water, were confirmed to be among the reaction products. We speculate that, similarly to the case of photooxidation of aromatic alcohols (see Krivtsov et al. ), the aldehyde is produced as the primary photocatalytic oxidation product, while octanoic acid is later formed from it by photooxidation or thermal oxidation via geminal diol formation, and finally octyl octanoate is produced by octanoic acid esterification with 1-octanol. The performance of the most efficient KPHI-HMDS photocatalyst was also studied under different light irradiation sources confirming its activity under simulated solar light irradiation using both AM 1.5G and 400 nm cut-off filter (Supplementary Information, Figure ).