Thiazole-Bimodulated Covalent Organic Frameworks for Synergistic Water Harvesting and Photosplitting

Vapor-phase photocatalytic hydrogen evolution offers a method to alleviate pure water scarcity, minimize mass transfer resistance, and avoid photocatalyst poisoning. Due to the limited research on water sorption kinetics and photogenerated charge carrier dynamics, the interaction mechanism between photocatalysts and water molecules remains unclear. Thus, we herein design covalent organic frameworks (COFs) using different thiazole configurations to enhance the efficiency of water harvesting and photosplitting. Crystallographic studies indicate that increased thiazole fusion in COFs can form one-dimensional open channels via tight π-π stacking to facilitate mass transfer. Electrostatic potential and adsorption energy analyses reveal the semihydrophobic trait of bis-thiazole, which modulates the vapor adsorption capacity of COFs with the hydrophilic ketone structure. Furthermore, transient absorption spectroscopy indicates that the electron-donating bis-thiazole, in conjunction with the keto structure, facilitates the separation of photogenerated charge carriers. Under the modulation of thiazole, water adsorption on COFs narrows their bandgap and optimizes electron transport, thus achieving a vapor-phase hydrogen evolution rate of 866 μmol h^-1 g^-1. This study sheds light on the design of vapor-phase photocatalysts and the synergistic effect between water harvesting and photosplitting, marking an advancement toward sustainable energy solutions.