Photocatalytic Hydrogen Evolution From Self‐Assembled Stacks of Pd–TCPP and Pt–TCPP

ABSTRACT The present work demonstrates that surfactant‐free precipitation of Pd– and Pt–TCPP in MeOH/H ₂ O yields well‐defined supramolecular architectures (µm‐long nanorods) whose photocatalytic function tracks their metal‐dependent photophysics and stacking. Among all tested M–TCPPs (M = Pd, Pt, Zn, Au, and Co), only Pd–TCPP and Pt–TCPP assemble to nanorods that are intrinsically active for H ₂ evolution without any Pt cocatalyst, with Pd–TCPP outperforming Pt–TCPP robustly across the optimal aggregation window (pH ≈ 4–5). In fact, the cocatalyst‐free Pd–TCPP nanorods surpass many other state‐of‐the‐art porphyrin platforms, including Zn–TCPP assemblies operated with high‐loaded Pt cocatalysts, as well as porphyrinic metal–organic frameworks (MOFs). The self‐assemblies display J‐type π–π stacking stabilized by carboxylate hydrogen bonding, producing broadened, red‐shifted light absorption and efficient charge transport. Correlating XRD analysis, spectroscopy, and electrochemistry reveals that compared to Pt–TCPP, Pd–TCPP nanorods exhibit tighter π–π stacking, extended triplet‐state lifetime, and lower charge‐transfer resistance, consistent with more efficient charge separation and faster interfacial electron transfer. Importantly, the approach taken in this work allows for one‐pot, surfactant‐free, co‐catalyst‐free operation of Pd–TCPP nanorods that not only is of low synthetic complexity but also avoids surfactant residues while delivering a high and stable photocatalytic H ₂ production activity under visible illumination.