A Porphyrinic Metal–Organic Framework Platform for Red-Light Photoredox Catalysis

Abstract

Low-energy photoredox catalysis has emerged as a powerful strategy for promoting mild, chemoselective transformations through radical intermediates. While various red-light-absorbing photocatalysts, including molecular porphyrins, have enabled diverse synthetic transformations, these processes operate almost exclusively under homogeneous conditions in organic solvents. Here, we demonstrate that integrating a photoactive porphyrin as the organic linker in a metal–organic framework (MOF) affords an air- and aqueous-compatible, heterogeneous photoredox catalyst. Using porphyrinic zirconium MOFs such as PCN-224, we enable a range of bond-forming reactions, including Giese additions, C(sp2)–H alkylations, C(sp2)–H arylations, formal cycloadditions, and radical polymerizations under mild red-light irradiation. While preserving the intrinsic reactivity of molecular porphyrins, heterogenization provides practical advantages including efficient photocatalysis independent of catalyst solubility and reaction medium, structural tunability, high turnover number (TON), and easy catalyst recovery and reuse. Mechanistic studies indicate that radical generation occurs predominantly within the framework pores.