Plasma-Induced Heptazine Distortion in Potassium Poly(heptazine imide) for Enhanced H2O2 Photosynthesis with Near-Infrared Response.

Photosynthesis is a promising strategy for hydrogen peroxide (H2O2) production, but its photocatalytic efficiency is limited by insufficient charge separation and a narrow light response. Here, we adopt a plasma treatment strategy to distort the heptazine unit structure in potassium poly(heptazine imide) (K-PHI) from a planar to a corrugated shape. The distortion of the heptazine unit in K-PHI enhances the dipole moment and built-in electron field in favor of efficient charge separation. Structural distortion in K-PHI alters the symmetry of heptazine rings, allowing partial coplanarity between n and π electron clouds. This corrugated structure promotes n → π* electronic transition, extending the visible light absorption. Meanwhile, potassium-heavy doping extends the lifetime of the photogenerated electrons and effectively increases the near-infrared light absorption intensity. Consequently, the corrugated K-PHI (CK-PHI-5) exhibits production rates of 11.6 mmol g-1 h-1 for H2O2 and 11.5 mmol g-1 h-1 for benzaldehyde. CK-PHI-5 also achieves exceptional near-infrared light-driven H2O2 production performance with rates of 1061.7 μmol g-1 h-1 at 808 nm and 697.7 μmol g-1 h-1 at 940 nm. This study demonstrates the use of PHI for photocatalytic H2O2 production using near-infrared light and develops a fast and effective plasma treatment method to awaken the structural distortion of PHI.