Subporphyrin Frameworks: A Missing Link Between Porphyrinoids and Porous Aromatic Networks

Subporphyrins represent a distinctive class of bowl-shaped, π-conjugated, and intrinsically electron-deficient macrocycles that exhibit photophysical and coordination behaviors unlike those of planar porphyrins. While current studies have primarily focused on the synthesis of subporphyrins with an increased number of aromatic rings and complex heterostructures, research on polymeric subporphyrin materials has not yet been reported. Herein, we report the first subporphyrin-based porous aromatic networks (PAF-HNU1 and PAF-HNU2) synthesized by coupling meso-functionalized subporphyrins with rigid aromatic linkers under solvothermal conditions. The frameworks exhibit extended π-delocalization and strong red-shifted absorption covering the UV-vis-NIR region, enabling efficient full-spectrum light harvesting. It was discovered that PAF-HNU2 exhibited high photogenerated charge separation and transport capabilities, as well as outstanding catalytic efficiency for a series of advanced oxidation reactions. Performance was two to three times that of PAF-HNU1 and its porphyrin-based PAF analogues. This work introduces a new family of subporphyrinic porous materials, providing the missing link between porphyrinoid chemistry and extended π-conjugated frameworks, and highlights their potential as a metal-free platform for next generation full-spectrum photocatalytic transformations.