Molecular-level design of isolated molybdenum oxide anchored on carbon nitride for photocatalytic H2 production and environmental remediation

Polymeric carbon nitride typically suffers from sluggish intrinsic charge separation and low available active sites. This paper reports that isolated non-crystalline molybdenum oxide species anchored to N-coordinating cavities (MoCN) have abundant surface-active sites for solid–liquid two-phase reactions, whether for photocatalytic H₂ evolution or organic pollutant degradation. Molecular dynamic simulations and density functional theory (DFT) revealed six-fold cavities to stabilize the MoO₃ species with non-crystalline features, endowing high dispersion and less aggregation. As proven in single-site heterogeneous catalysts, the photocatalyst benefits from size reduction and accelerated interfacial charge transfer because of its mutual contact between two semiconductors. The MoCN shows a high visible-light H₂ evolution of 1265 µmol g⁻¹h⁻¹ under visible light (λ ≥ 400 nm) illumination. The photocatalyst degraded more than 95% tetracycline within 30 min and rhodamine B in 10 min. The MoO₃ species confined within π-conjugated systems increase the catalytic contact sites, extending visible light harvesting ability to a longer wavelength. Each single catalytic site facilitates the separation and transfer of charge carriers while interfacial charge still occurs between MoO₃ and CN. This molecular-level design and strategy provide a new opportunity and a universal way to extend the boundaries of liquid–solid phase catalysts.