Tailored Surface Microenvironment of Molecular Nanophotocatalysts for Boosting Photocatalytic Hydrogen Evolution

Organic photocatalysts are an attractive platform for solar-to-chemical energy conversion, but their performance is often constrained by bulk aggregation, poor light penetration, and rapid exciton recombination. Although surfactant-assisted nanostructuring can help alleviate aggregation, surfactants are generally treated as passive stabilizers with little direct influence on photocatalytic function. Here we show that surfactants can actively engineer the interfacial microenvironment of organic nanophotocatalysts, leading to substantially enhanced photocatalytic hydrogen evolution. A donor-acceptor small molecule, CNP90, is co-assembled with either hydrophilic polyethylene glycol (PEG) or amphiphilic Tween surfactants (Tween 20, T20; Tween 80, T80) via nanoprecipitation to afford a series of tailored nanophotocatalysts. Although all surfactants improve colloidal stability, T20/CNP90 exhibits markedly enhanced photoluminescence quantum yield and charge generation, leading to a more than 16-fold increase in the hydrogen evolution rate to 520.17 mmol g^-1 h^-1, among the highest values reported for organic photocatalysts. Spectroscopic studies combined with molecular dynamics simulations reveal that T20 constructs an amphiphilic interfacial microenvironment around CNP90, comprising a hydrophobic inner shell that suppresses nonradiative recombination and a hydrophilic outer corona that promotes water access to catalytic sites. These insights establish surfactant-driven microenvironment engineering as a powerful, low-cost, and generalizable paradigm for maximizing the performance of organic photocatalysts.