Red light penetrates approximately 23 times further into reaction solutions than blue light, reaching a depth of 12 cm before 90% of its power is absorbed by the solution. 44 To highlight the utility of red light-promoted cross-coupling reactions, we performed a gram-scale reaction of aryl bromide and n-butylamine in a round-bottom flask with a diameter of 10 cm, which yielded tetracaine (226) in 85% yield (Figure ), further demonstrating the utility of red light's penetration ability in this semihomogeneous catalysis. Impressively, even when simulated solar light was used as the light source, tetracaine was obtained in 86% yield (Figure , sections 4.5 and 4.7 in Supporting Information). Additionally, the yield of tetracaine was 59% when the reaction was carried out under solar light for 5 h (Figure , section 4.4 in Supporting Information). Furthermore, a significant advantage of this method is that the photocatalyst CN-OA-m could easily be recycled and reused (Figure ; and see section 5 in Supporting Information). After the reaction was complete (24 h), the CN-OA-m powder was recovered by centrifugation and then washed. Fourier transform IR spectroscopy (Figure ), UV-vis spectroscopy (Figure ), transmission electron microscopy (Figures S22 and S23 Next, we carried out mechanistic studies. The UV-vis spectrum of the prepared CN-OA-m showed an absorption band in the red-light region (Figure ). Additionally, after a solution of CN-OA-m in DMAc was irradiated with red light for 10 min, a signal with a g value of 2.003 was observed in the electron paramagnetic resonance spectrum (Figure ; and see section 11.3 of Supporting Information), a finding that is consistent with literature reports 63, 67 and that suggests that red-light irradiation produced electrons. Moreover, the progress of the red-light-promoted reaction slowed dramatically after the addition of an electron (e -) sacrificer (AgNO3 or KI) or a hole (h + ) sacrificer (Na2S/Na2SO3 or EDTA) (Figure ; and see section 7 of Supporting Information). 68, 86 These results confirm that red-light excitation of photogenerated charges played a major role in this photocatalytic coupling reaction. Furthermore, when CN-OA-m (2 mg) was used as the photocatalyst and a Ni(II)(ligand)Br2 complex was the metal catalyst under red-light irradiation for 90 min, electron paramagnetic resonance spectroscopy revealed a distinct signal at gavg = 2.204 (Figure ; and section 11 of Supporting Information), 91, 94-95 indicating the formation of a Ni(I) species. Therefore, we speculate that upon red-light excitation, CN-OA-m served as an electron donor to reduce the Ni(II)(ligand)Br2 complex to a Ni(I) species via a singleelectron transfer. In addition, in the absence of substrates, the putative Ni(I) species generated in situ from the Ni(II)(ligand)Br2 complex was irradiated with red light for 90 min in the presence of CN-OA-m; and then an aryl bromine and an amine were introduced and allowed to react in the dark for 24 h. This experiment delivered the desired product in 29% yield by NMR spectroscopy (see section 10.2 of Supporting Information). These results indicate that under red-light irradiation, a catalytically active Ni(I) species was generated.