Ultrastable porphyrin covalent organic framework with protected imine linkages for highly efficient and sustainable photocatalytic oxidation of amines

Abstract

The stability of emerging covalent organic frameworks (COFs) is of paramount importance in their practical applications. However, effective strategies to enhance the stability of vulnerable COFs are barely reported and remain significant challenges. Herein, a robust bulky diamine ligand (NMind) was used as linker and protecting group to readily construct the imine-protected MindTPP-COF combined with typical porphyrin building block (TFPP). Owing to the rigidity of NMind and its constraints of structural dynamics, the MindTPP-COF shows adequate porosity with remarkable thermal, photo- and chemical stability. Based on the exceptional stability of the MindTPP-COF, a robust and long-term sustainable photocatalytic system can be established for selective oxidation of a variety of amines in excellent yields and gram-scale. Notably, the MindTPP-COF exhibits preserved catalytic robustness and structural integrity after 12 catalytic cycles, verifying great improvements compared with the imine-unprotected isostructural Por-COF. This work provides inspirations for the design and synthesis of ultrastable COFs promising for practical applications as efficient and sustainable heterogeneous catalysts.