This study explores the development of highly efficient carbon-doped carbon nitride (C-doped SS-CN) for sustainable green hydrogen production through photocatalytic water splitting. Carbon nitride, a metal-free semiconductor, has unique properties that make it suitable for photocatalytic applications, but it suffers from fast charge-carrier recombination and low charge transfer efficiency. The researchers used a supramolecular approach to couple thiourea and trimesic acid, creating C-doped SS-CN with precise π-electron density manipulation. This method resulted in fine-tuned band positions, reduced electron-hole recombination, and enhanced conductivity, leading to significantly improved hydrogen generation under solar-simulated light. Advanced analytical techniques, including X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and electron paramagnetic resonance (EPR) spectroscopy, were employed to characterize the C-doped SS-CN. The study also utilized first-principles calculations to understand the electronic structure and energetics of doping. The optimized C-doped SS-CN demonstrated a fivefold increase in photocatalytic hydrogen production, bringing the research closer to achieving a green hydrogen economy.This study explores the development of highly efficient carbon-doped carbon nitride (C-doped SS-CN) for sustainable green hydrogen production through photocatalytic water splitting. Carbon nitride, a metal-free semiconductor, has unique properties that make it suitable for photocatalytic applications, but it suffers from fast charge-carrier recombination and low charge transfer efficiency. The researchers used a supramolecular approach to couple thiourea and trimesic acid, creating C-doped SS-CN with precise π-electron density manipulation. This method resulted in fine-tuned band positions, reduced electron-hole recombination, and enhanced conductivity, leading to significantly improved hydrogen generation under solar-simulated light. Advanced analytical techniques, including X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and electron paramagnetic resonance (EPR) spectroscopy, were employed to characterize the C-doped SS-CN. The study also utilized first-principles calculations to understand the electronic structure and energetics of doping. The optimized C-doped SS-CN demonstrated a fivefold increase in photocatalytic hydrogen production, bringing the research closer to achieving a green hydrogen economy.