Orchestrating Excited‐State Energy Flow in Benzobisthiazole Covalent Organic Frameworks for Solar Water Evaporation and H ₂ O ₂ Production

ABSTRACT The competing pathways of photothermal conversion and photocatalytic H 2 O 2 production present a long‐standing challenge in solar energy utilization, as efficient nonradiative dissipation inherently suppresses the long‐lived excited states required for catalysis. Herein, we demonstrate a precise molecular engineering strategy to orchestrate excited‐state energy flow in isoreticular benzobisthiazole‐linked covalent organic frameworks (BBT‐COFs) via post‐synthetic linker exchange. By rationally introducing steric hindrance (BBT‐TAPB), intramolecular motions and nonradiative decay are boosted for exceptional photothermal heating. In contrast, a strong donor–acceptor (D–A) architecture (BBT‐BTT) enhances intersystem crossing and triplet‐state population for singlet oxygen‐mediated H 2 O 2 photosynthesis. When integrated into a self‐rotating hydrogel evaporator, these COFs enable a dual‐functional solar‐driven platform for water evaporation and H 2 O 2 generation. Under 1‐sun irradiation, the BBT‐TAPB‐based hydrogel delivered an evaporation rate of 1.82 kg m −2 h −1 , whereas the BBT‐BTT‐based hydrogel achieved an H 2 O 2 production rate of 143 mM m −2 h −1 . This work highlights a cooperative regulation between molecular motion and D–A interactions in modulating excited‐state energy dissipation, providing a modular blueprint for tuning photothermal and photocatalytic solar energy conversion processes.