AbstractIn recent years, the development of photocatalysts based on noncovalent strategies has shown an important role in medical and organic materials. Herein, an organic fluorescent dye benzothiazole derivative (2‐(N,N‐diethylanilin‐4‐yl)‐4,6‐bis(3‐methylpyrazol‐1‐yl)‐1,3,5‐triazine [MPBT]) was designed and synthesized. It was encapsulated in the cavity of cucurbit[8]uril (CB[8]) to form a supramolecular dimer through host–guest interaction, which converted the dye into a highly efficient photocatalyst. With the formation of 2MPBT‐CB[8] supramolecular dimer, the emergence of host‐enhanced charge transfer interactions could significantly facilitate singlet to triplet through intersystem crossing. At the same time, the alternating structure of 2MPBT‐CB[8] facilitated the triplet states for further energy transfer and electron transfer. In addition, the electron transfer process with electron donor generated cationic free radical and photocatalyst negative ion free radical (), which in turn reacted with oxygen (O₂) to form superoxide anion radical (). The generated could be used to catalyze the oxidative hydroxylation of aryl boronic acid. Therefore, the 2MPBT‐CB[8] had become a highly efficient photocatalyst for the oxidative hydroxylation of aryl boronic acid. This strategy of supramolecular dimerization provides a new strategy for the development of new photocatalysts based on noncovalent interactions.