LaFeO3 nanospheres with an orthorhombic perovskite structure were synthesized by a sol–gel autocombustion method in the presence of different citric acid ratios (x ¼ 2, 4, 8, and 16) and utilized for the photocatalytic conversion of o-aminophenol (OAP) to 2-aminophenoxazine-3-one (APX) for the first time. OAP is one of the most toxic phenolic derivatives used as a starting material in many industries; however, the dimerization product APX has diverse therapeutic properties. Photocatalytic conversion was carried out in ethanol/water and acetonitrile/water mixtures in the absence and presence of molecular oxygen at ambient temperature via the oxidative coupling reaction that mimics phenoxazinone synthase-like activity. The LaFeO3 samples showed a superior photocatalytic activity of OAP to APX with rate constants of 0.43 and 0.92 min1 in the absence and presence of molecular oxygen, respectively. Thus, the LaFeO3 nanozymes could be used as promising candidates in industrial water treatment and phenoxazinone synthase-like activity