Engineering Ionic Carbon Nitride for Photocatalytic H₂O₂ Production and CO₂ Reduction

Artificial photosynthesis offers a promising route for converting solar energy into fuels and value-added chemicals under mild conditions. Its development, however, requires photocatalysts that combine visible-light absorption, charge separation, and selective molecular activation. Ionic carbon nitrides, particularly potassium poly(heptazine imide) (KPHI), are attractive because their structure, defects, and interfaces can be tailored. Here, we present KPHI as a versatile platform for solar chemical synthesis. NH₃-guided nanostructural refinement provides a route for tuning visible-light-driven H₂O₂ production, while control over the synthesis environment may reduce the thermal demands of material preparation. Building on this structural control, we integrate cobalt phthalocyanine (CoPc) with KPHI to create a molecular-semiconductor interface. Guided by molecular electrocatalysis, this hybrid platform allows us to explore how molecular coupling influences interfacial charge transfer, O₂ activation, and H₂O₂ formation.We further extend this materials concept toward photocatalytic CO₂ reduction, focusing on the interplay between the intrinsic reactivity of KPHI and the cobalt-containing interface. The identity of the catalytic sites, the role of interfacial cooperation, and the pathways governing product formation remain central questions. Our findings will be presented together with mechanistic insights into how defect and interface engineering can broaden the photocatalytic reactivity of ionic carbon nitrides.