Rational Fabrication of a Robust, Exfoliatable Catechol-Porphyrin Covalent Network for Enhanced H₂O₂ Photosynthesis

Covalent organic frameworks (COFs) containing dioxin-linkages are highly valued for their exceptional chemical stability, which is essential for practical use. However, research on dioxin-based COFs remains limited. Herein, a unique nonplanar 2D COF, designated as TCP-COF, constructed from catechol-porphyrin units interconnected by 1,4-dioxin bonds, exhibiting a staggered AAA stacking pattern, is presented. Remarkably, TCP-COF can undergo in situ exfoliation to produce ultrathin 2D nanosheets when it is utilized as a photocatalyst for hydrogen peroxide (H₂O₂) generation in water and air, without the need for additives. This exfoliation process is primarily driven by the distortion of porphyrin units and weak π-π interaction between adjacent layers in TCP-COF. The resultant ultrathin nanosheets significantly reinforce catalytic activity, achieving a photocatalytic H₂O₂ production rate of 3077 µmol g^-1 h^-1. The mechanism underlying H₂O₂ photosynthesis is further explored through a combination of experimental analyses and theoretical calculations. This study provides valuable insights for the development of efficient COF-based photocatalysts for H₂O₂ evolution.