Through first-principles computations on the structural, electronic, and optical properties of perfect and defective two-dimensional C2N crystals, the effects of point defects on photoelectronic characteristics of this potential photocatalysts were investigated. The introduction of point defects, including N vacancies, interstitial C impurities, O@C and H@N dopants, and the interstitial O in the benzene ring and big ring, should result in more appropriate band structures and broadened optical absorptions and generally promoted carrier mobilities of C2N photocatalysts. Remarkably, the defective C2N with N vacancy, interstitial O in benzene/big ring, and interstitial C in benzene ring are highly recommended for the photocatalytic applications due to their broadened optical absorption, spatially separated e––h+ pairs, excellent redox capacities, and fast carrier migrations. Our theoretical results can provide some guidance for further exploring the utilization of 2D C2N material and some possible strategies ...