Utilization of g-C₃N₄ as a single photocatalyst material without combination with other semiconductor remains challenging. Herein, we report a facile green method for synthesizing a metal free modified g-C₃N₄ photocatalyst. The modification process combines four different strategies in a one-pot thermal reaction: non-metal doping, porosity generation, functionalization with amino groups, and thermal oxidation etching. The as-prepared amino-functionalized ultrathin nanoporous boron-doped g-C₃N₄ exhibited a high specific surface area of 143.2 m² g⁻¹ which resulted in abundant adsorption sites for CO₂ and water molecules. The surface amino groups act as Lewis basic sites to adsorb acidic CO₂ molecules, which can also serve as active sites to facilitate hydrogen generation. Besides, the simultaneous use of ammonium chloride as a dynamic gas bubble template along with thermal oxidation etching …