Nitric acid (HNO3) has garnered attention as a versatile acid reagent in laboratory and industrial settings, primarily known for its role in explosives and fertilizer production. Recent studies have explored its application in catalytic processes, particularly in electro- and photo-catalysis, including its involvement in nitrogen fixation and oxidation. This study investigates the photo-catalytic performance of HNO3 in the conversion of mesitylene to 3,5-dimethylbenzaldehyde, an industrially significant compound. Our results reveal successful conversion under irradiation conditions, with systematic optimizations indicating an optimal concentration of 0.2 M HNO3. Mechanistic studies employing scavenger assays suggest the involvement of hydroxyl radicals in the formation of aldehydes. Furthermore, synergistic effects between HNO3 and phosphorus corrole photosensitizers enhance catalytic performance. Subsequent optimization of reaction conditions yields a maximum yield of 45 % for 3,5-dimethylbenzaldehyde. Expansion of the scope to include toluene derivatives demonstrates varying yields, influenced by substituent effects. Notably, the combination of HNO3 with the corrole catalyst leads to improved yields compared to HNO3 alone. These findings underscore the potential of HNO3 as a photo-catalyst and highlight opportunities for novel catalyst design in practical applications.