In this work, B and K were introduced into the heptazine structure of carbon nitride to synthesize the catalyst kalium-boron doped carbon nitride (KBCN) with a larger light absorption range and improved photogenerated carrier separation rate. Boron atoms are introduced into the carbon nitride heptazine units to optimize the electronic structure within the carbon nitride planes, and the B-N bonds formed by the heptazine units facilitate charge transfer. Potassium atoms are introduced into the carbon nitride interlayer as charge transfer channels to synergistically promote the transfer of photogenerated electrons. This work provides a potential idea for the doping of metallic and nonmetallic elements to jointly promote the charge distribution and transfer of carbon nitride.