Metal-free carbon dots toward bio-green hydrogen evolution via photocatalysis

Hydrogen (H2) has emerged as a therapeutic agent with potent antioxidative and anti-inflammatory effects, offering promising applications in the treatment of neurological and cardiovascular diseases. However, the development of controllable, clean, and in situ H2 generation strategies remains a significant challenge in biological systems. Herein, we report a metal-free carbon dot (CD) based photocatalyst synthesized via thermal polymerization of uracil, is capable of efficient and biocompatible photocatalytic H2 evolution. The photocatalyst exhibits a well-defined structure composed of interconnected C–N five-membered rings, where nitrogen atoms serve as active sites for proton adsorption and reduction. Under simulated physiological conditions, the photocatalyst enables H2 production without water oxidation or oxidative side reactions, thereby maintaining the ion concentration and pH stability. A H2 evolution rate of 73.87 μmol h−1 g−1 is achieved, and tunable H2 release is realized by varying the catalyst dosage, illumination time, and light intensity. Importantly, cytocompatibility tests reveal an enhanced cell viability of up to 165.6%, demonstrating the excellent biocompatibility and the potential of this system as a bio-green platform for therapeutic H2 delivery.