<p>The characteristic of photochemical organic synthesis lies in the distinctive redox properties of excited-state photocatalysts, which could avoid using stoichiometric redox reagents, thereby enabling green and sustainable transformations. However, the conversion efficiency of light-to-chemical energy is a key bottleneck limiting the large-scale application. Herein, we synthesize ultra-thin graphitic carbon nitride nanosheets by regulating precursor types and thermal protocols. In photochemical Minisci-type cross-couplings, this ultra-thin carbon nitride exhibits high catalytic efficiency, achieving rates of 40 mmol g_cat⁻¹ h⁻¹ under LED irradiation and 10.9 mmol g_cat⁻¹ h⁻¹ under natural sunlight. The photocatalyst’s high specific surface area (120 m² g⁻¹) enhances substrate adsorption capacity and accelerates surface electron transfer, boosting photocatalytic efficiency. Furthermore, the material demonstrates excellent recycling stability, and the reaction system was successfully scaled to gram-level, highlighting its potential for industrial applications.</p>