To our delight, the desired para-selective product (3a) was isolated in 67% yield with a p/m ratio of 8:1 (Table , entry 1). Alternative commonly available solvents such as DCE, DMF, DMSO, EtOH, HFIP proved to be unfavorable in terms of both yield and the selectivity ratio (Table , entries 2-6). In an endeavor to enhance the p/m ratio, different light sources with varying wavelengths (427 nm and 456 nm Kessil lamps) were explored and led to the yields of 65% and 61%, respectively, with a p/m ratio of 10:1 (Table , entries 7-8). This investigation motivated the adoption of a lower-energy light source (a blue LED strip) for the transformation and in fact, with the utilization of this LED strip, the targeted product 3a was obtained with a yield of 64% with a 10:1 p/m ratio in 6 hr (Table , entry 10). Our hypothesis suggested that the selectivity of this transformation was mainly driven by the interaction between the metal catalyst and the substrate. When using high-energy light sources, the intermediate tends to break apart easily, leading to less selective outcomes. In contrast, the lower energy from blue LEDs helped to maintain the integrity of the intermediate, making it more suitable for our reaction and enhancing selectivity. After the allotted reaction time, we found that about 70% of the starting aromatic compounds had reacted, suggesting that they might not be very reactive. Meanwhile, the trifluoromethylating reagent, which was in excess, started to break down into a known side product (S2.9, ESI). Extending the reaction time further did not improve the yields or the conversion rate. The use of other trifluoromethylating reagents such as CF3SO2Cl, Togni-II and Umemoto's reagent did not also provide satisfying results (Table , entries 11-13). Notably, in the absence of light, no product was formed, unequivocally affirming the pivotal role of photons in this reaction (Table , entry 14). Only 10% of the desired product was obtained when the photocatalyst was omitted from the reaction (Table , entry 15). Furthermore, we have performed a large-scale reaction with 25 mmol of 1a (3 gram, see S2.5) and this scale-up reaction yielded 52% of the product by maintaining a 10:1 p/m ratio. Additionally, to assess the stability of the photocatalyst, a photocatalytic trifluoromethylation reaction of nitrobenzene (1a) with Togni-I (2a) was recycled for at least 7 consecutive cycles under the identical reaction conditions (Scheme 1B, S2.