Molecular self-assembly is a natured-inspired strategy to integrate individual functional molecules into supramolecular nanostructured materials through noncovalent bond interactions for solar to fuel conversion. However, the design and engineering of the morphology, size, and orderly stacking of supramolecular nanostructures remain a great challenge. In this study, regular porphyrin nanocrystals with different orderly stacked structures are synthesized through noncovalent self-assembly of Pt(II) meso-tetra (4-carboxyphenyl) porphine (PtTCPP), using surfactants with different electronegativity. The synergy of noncovalent bond interactions between porphyrin molecules, and between porphyrin molecules and surfactants resulted in different molecular packing patterns. Due to the spatial ordering of PtTCPP molecules, the different nanocrystals exhibit both collective optical properties and morphology-dependent activities in photocatalytic hydrogen production. The measurements of the photodeposition of dual cocatalysts showed that the photogenerated electrons and holes selectively aggregated at different active sites, revealing separation pathways and directional transfer of photogenerated electrons and holes in the assemblies. This study provides a new strategy to exert rational control over porphyrin self-assembly nanocrystals for highly efficient water splitting.

Nanoparticle photosensitizers possess technical advantages for photocatalytic reactions due to enhanced light harvesting and efficient charge transport. Here we report synthesis of semiconductor nanoparticles through covalent coupling and assembly of metalloporphyrin with condensed carbon nitride. The resultant nanoparticles consist of light harvesting component from the condensed carbon nitride and photocatalytic sites from the metalloporphyrins. This synergetic particle system effectively initiates efficient charge separation and transport and exhibits excellent photocatalytic activity for CO₂ reduction. The CO production rate can reach up to 57 μmol/(g·h) with a selectivity of 79% over competing H₂ evolution. Controlled experiments demonstrate that the combination of light harvesting with photocatalytic activity via covalent assembly is crucial for the high photocatalytic activity. Due to effective charge separation and transfer, the resultant nanoparticle photocatalysts show exceptional photo stability against photo-corrosion under light irradiation, enabling for long-term utilization. This research opens a new way for the development of stable, effective nanoparticle photocatalysts using naturally abundant porphyrin pigments.