Metalated Porphyrin–Naphthalimide Sensitizers Boost TiO ₂ Photocatalysis for Solar Hydrogen Evolution

ABSTRACT We report a series of porphyrin–naphthalimide dye‐sensitized photocatalytic systems (PNDSPs) by integrating tailored porphyrin–naphthalimide photosensitizers with a Pt‐loaded TiO 2 catalyst (TiO 2 /Pt, denoted as PCT) for efficient visible‐light‐driven hydrogen evolution. The photosensitizer library includes a metal‐free dye, PN1 (6,6′‐(((5Z,9Z,15Z,19Z)‐10,20‐bis(2,6‐bis(octyloxy)phenyl)‐22H,24H‐porphyrin‐5,15‐diyl) bis(ethyne‐2,1‐diyl)) bis (2‐hexa decyl‐1H‐benzo[de] isoquinoline‐1,3(2H)‐dione)) and its metal‐substituted analogues PN2‐PN4, incorporating Ni, Cu, and Zn, respectively. Among all sensitized systems, PCT@PN2 delivered the highest hydrogen evolution rate, outperforming PCT@PN1, PCT@PN3, and PCT@PN4 under identical conditions. Photocatalytic performance was assessed under neutral (pH 7), acidic (pH 3), and basic (pH 10) aqueous environments using triethanolamine (TEOA) as a sacrificial electron donor. The results demonstrate that the naphthalimide–porphyrin conjugation strategy, coupled with precise modulation of electron‐rich and electron‐deficient π‐linkers between the chromophores, substantially enhances visible‐light absorption, accelerates charge separation, and boosts photonic energy conversion efficiency.