Surface Charge Modulation in Covalent Organic Frameworks for Controlled Pt‐Photodeposition and Enhanced Photocatalytic Hydrogen Evolution
Klaudija Paliušytė, Lucas L. Nascimento, Hannah Illner, Max Wiedmaier, Roman Guntermann, Markus Doeblinger, Thomas Bein, Antônio Otávio T. Patrocínio, Jenny Schneider
Abstract
Abstract Covalent organic frameworks (COFs) represent a new class of organic photocatalysts for the hydrogen evolution reaction (HER). While the influence of COF structural and optoelectronic properties on HER is well‐studied, the role of surface charge in optimizing interfacial interactions with reactants remains underexplored. In this study, it is demonstrated that converting imine to amide linkages in a thiophene‐based COF allows for altering surface charge through different protonation behaviors of the linkages. Zeta potential measurements reveal that the amide‐linked COF, due to its lower basicity, is deprotonated and negatively charged in the presence of ascorbic acid, while the imine‐linked COF is protonated and positively charged. This electrostatic contrast drives the photoreduction of [PtCl 6 ] 2 ⁻ to Pt, with the imine‐linked COF yielding uniformly distributed small Pt particles (1–2 nm), whereas the amide‐linked COF forms larger Pt particles (up to 100 nm). The amide‐linked COF, acting as an antenna that facilitates interdomain electron transport along COF agglomerates, promotes both Pt growth and subsequent proton reduction demonstrating a 300% increase in photocatalytic HER rate compared to its imine form. This work introduces surface charge modulation as a novel tool for controlling photocatalytic processes in COF‐based systems expanding the COF functionality in photocatalysis.