Exploring the Influence of Metal Incorporation and Porosity Optimization on the H₂O₂ Production Efficiency of Templated Poly(Heptazine Imides)

Hydrogen peroxide (H 2 O 2 ) is a versatile chemical, valued as both a promising energy carrier and a widely used oxidizing agent in disinfection and organic synthesis. The light‐driven catalytic oxygen reduction reaction (ORR) using carbon nitrides (CN x ) is based on the conversion of solar into chemical energy and thus offers a sustainable pathway for decentralized H 2 O 2 production. This study presents a novel synthetic strategy for producing ionic derivatives of CN x , specifically poly(heptazine imides) (PHIs) with higher specific surface areas, using an ordered mesoporous silica material (SBA‐15) as a template. The templated PHIs exhibit enhanced porosity, controlled incorporation of transition metals, improved visible‐light absorption, tunable hydrophilicity and more efficient charge separation compared to bulk CN x . PHIs containing iron, cobalt or nickel accelerate H 2 O 2 decomposition, whereas templated potassium PHI (KPHI) achieves a 2.1‐fold increase in H 2 O 2 production with ethanol as a hole scavenger under visible light irradiation (455 nm, 50 mW·cm −2 ) compared to bulk KPHI (KPHI_b). A high H 2 O 2 production rate of 19.0 mmol·L −1 ·h −1 (i.e., 76.2 mmol·g −1 ·h −1 ) under the same irradiation condition is achieved with KPHI in a 90 vol.% methanol solution and an optimal photonic yield of 12.8% is obtained with KPHI at 365 nm.