Guest-Induced Structural Torsion in Single Covalent Organic Frameworks for Enhanced Photocatalysis.

Liu, Yang; Chi, Hongbing; Tan, Yifei; Chen, Zhengguo; He, Yi · Nano Lett · 2025

basic_science · Level V

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Abstract

Monitoring and understanding the photocatalytic reactions at individual covalent organic framework (COF) photocatalysts are crucial for gaining insights into their structure-activity relationships. Here, we report real-time imaging of the guest-induced structural torsion in single COF-300 microcrystals for enhanced photocatalysis utilizing <i>in situ</i> dark-field optical microscopy (DFM). Upon inclusion of ethyl acetate (EAC) into the COF-300 framework, deformed EAC-encapsulated COF-300 (EAC@COF-300) microcrystals with twisted diimine linkers are generated, resulting in an inert-to-active photocatalytic reactivity transformation. Impressively, this host-guest-enhanced photocatalysis strategy is also applicable to other guests. The combination of single-particle imaging, spectral characterizations, and theoretical calculations elucidates that structurally twisted EAC@COF-300 boosts the intersystem crossing process and spin-orbit coupling, facilitating the separation of photogenerated electron-hole pairs. Furthermore, the twisted EAC@COF-300 realizes the photocatalytic removal of radioactive <sup>131</sup>I<sup>-</sup> at the pg level. Our findings provide a general strategy for the rational design of efficient COF photocatalysts via twist engineering.