Photogeneration of Hydrogen in Water via Self-Assembly-Induced Colloidal Covalent Organic Framework Particles

The synthesis of colloidal imine-linked Covalent Organic Framework nanoparticles using a polymeric growth-blocking agent that facilitates both in situ colloidal stabilization and size control. This new surfactant-free method, called Self-Assembly-Induced Colloidal Covalent Organic Frameworks (SAI2COF), is inspired by Polymerization-Induced Self-Assembly (PISA), largely used to generate colloidal emulsions. The optimized formulation, I-COF-Poly-0.5, shows excellent colloidal stability in aqueous media under neutral and acidic conditions, along with enhanced light absorption and π-conjugation. Photocatalytic hydrogen evolution demonstrates that I-COF-Poly-0.5 is an efficient light-driven catalyst for at least 24 h, with performance strongly influenced by the sacrificial electron donor (SED), photocatalyst concentration, and metal cocatalyst. Sodium ascorbate is identified as the most effective SED for sustained H₂ production, whereas triethanolamine induces rapid deactivation. An optimal COF concentration of 0.1 g L^-1 provides the best balance between light penetration and catalytic efficiency. Among tested cocatalysts, platinum salts (H₂PtCl₆, K₂PtCl₆) significantly outperform AgNO₃, which forms less active silver nanoparticles. Single-particle induced coupled plasma mass spectrometry confirms the formation of hybrid colloidal COF particles containing in situ photo-generated metal nanoparticles. Overall, this surfactant-free approach affords stable, dispersed COF photocatalysts for clean hydrogen production over 24 h without aggregation and paves the way for further optimization.