Self‐Floating Pt‐Nanoparticle‐Loaded Conjugated Polymer Photocatalyst Enables Efficient H ₂ O ₂ Production in Pure Water

Organic conjugated polymers are attractive candidates for sustainable photocatalytic H ₂ O ₂ production, but their activity is often constrained by sluggish O ₂ diffusion, a scarcity of active sites, and limited solar energy utilization. Herein, we develop a self‐floating photocatalyst, Pt@MBP, consisting of platinum (Pt) nanoparticles anchored on triazine‐biphenyl conjugated polymer nanosheets. Pt@MBP is prepared through calcination of a melamine‐biphenyl‐4,4′‐dicarboxylic acid supramolecular precursor followed by photodeposition of Pt. Owing to its floatable feature, Pt@MBP effectively captures atmospheric O ₂ at the gas–liquid interface and enhances visible‐light harvesting. The ultrathin MBP nanosheets facilitate charge separation and migration, while the well‐dispersed Pt nanoparticles function as electron sinks and catalytic centers for O ₂ adsorption and activation, thereby lowering the energy barrier for the oxygen reduction (ORR) pathway. As a result, Pt@MBP achieves a H ₂ O ₂ production rate of 2352 μmol g ⁻¹ h ⁻¹ in pure water. This work establishes a rational design of self‐floating polymer photocatalysts for efficient solar‐to‐chemical conversion.