Tetrazine‐Linked Covalent Organic Frameworks With Acid Sensing and Photocatalytic Activity

Abstract The first synthesis and comprehensive characterization of two vinyl tetrazine‐linked covalent organic frameworks (COF), TA‐COF‐1 and TA‐COF‐2, are reported. These materials exhibit high crystallinity and high specific surface areas of 1323 and 1114 m² g⁻¹. The COFs demonstrate favorable band positions and narrow band gaps suitable for light‐driven applications. These advantages enable TA‐COFs to act as reusable metal‐free photocatalysts in the arylboronic acids oxidation and light‐induced coupling of benzylamines. In addition, these TA‐COFs show acid sensing capabilities, exhibiting visible and reversible color changes upon exposure to HCl solution, HCl vapor, and NH₃ vapor. Further, the TA‐COFs outperform a wide range of previously reported COF photocathodes. The tetrazine linker in the COF skeleton represents a significant advancement in the field of COF synthesis, enhancing the separation efficiency of charge carriers during the photoreaction and contributing to their photocathodic properties. TA‐COFs can also degrade 5‐nitro‐1,2,4‐triazol‐3‐one (NTO), an insensitive explosive present in industrial wastewater, in 20 min in a sunlight‐driven photocatalytic process; thus, revealing dual functionality of the protonated TA‐COFs as both photodegradation and Brønsted acid catalysts. This pioneering work opens new avenues for harnessing the potential of the tetrazine linker in COF‐based materials, facilitating advances in catalysis, sensing, and other related fields.