Calix[4]arene‐Derived 2D Covalent Organic Framework with an Electron Donor–Acceptor Structure: A Visible‐Light–Driven Photocatalyst

Abstract

The calixarenes are ideal building blocks for constructing photocatalytic covalent organic frameworks (COFs), owing to their electron‐rich and bowl‐shaped π cavities that endow them with electron‐donating and adsorption properties. However, the synthesis and structural confirmation of COFs based on calixarenes are still challenging due to their structural flexibility and conformational diversity. In this study, a calix[4]arene‐derived 2D COF is synthesized using 5,11,17,23‐tetrakis(p‐formyl)‐25,26,27,28‐tetrahydroxycalix[4]arene (CHO‐C4A) as the electron donor and 4,7‐bis(4‐aminophenyl)‐2,1,3‐benzothiadiazole (BTD) as the acceptor. The powder X‐ray diffraction data and theoretical simulation of crystal structure indicate that COF‐C4A‐BTD exhibits high crystallinity and features a non‐interpenetrating undulating 2D layered structure with AA‐stacking. The density functional theory theoretical calculation, transient‐state photocurrent tests, and electrochemical impedance spectroscopy confirm the intramolecular charge transfer behavior of COF‐C4A‐BTD with a donor–acceptor structure, leading to its superior visible‐light–driven photocatalytic activity. COF‐C4A‐BTD exhibits a narrow band gap of 1.99 eV and a conduction band energy of −0.37 V versus normal hydrogen electrode. The appropriate energy band structure can facilitate the participation of ·O2− and h+. COF‐C4A‐BTD demonstrates high efficacy in removing organic pollutants, such as bisphenol A, rhodamine B, and methylene blue, with removal rates of 66%, 85%, and 99% respectively.