Controlled assembly of two-dimensional porphyrin heterostructures toward directed energy transfer and charge separation

The exceptional efficiency of natural light-harvesting systems arises from their precisely organized supramolecular architectures. Reproducing such structural control in synthetic aqueous assemblies, particularly over size and dimensionality, remains a formidable challenge. Here, we report a general seeded-growth strategy that enables precise, hierarchical assembly of two-dimensional (2D) porphyrin heterostructures in water. Integrating π–π stacking, hydrogen bonding, and hydrophobic interactions, the porphyrin amphiphiles follow a metastable assembly pathway that yields kinetically controlled nanosheets or heterostructures. This approach provides unprecedented control over the nanostructure area across two orders of magnitude, establishing a versatile platform for complex functional architectures. By integrating a cobalt–porphyrin acceptor via block co-assembly, we construct 2D donor–acceptor heterostructures that achieve a directed energy funneling. Ultrafast spectroscopic analysis combined with global fitting reveals the mechanism: the controlled 2D heterostructures promote exciton migration at rates 2.5-fold greater than in homostructures and drive the formation of a fully charge-separated state on a sub-nanosecond timescale, with dynamics that scale with platelet dimensions. This work establishes a synthetic route to biomimetic 2D heterostructures and elucidates the structural determinants of directed exciton and charge flow, offering key design principles for advanced biomimetic systems. Reproducing the structural control of natural organized supramolecular architectures in synthetic aqueous assemblies remains challenging. Here, we report a general seeded-growth strategy that enables precise, hierarchical assembly of two-dimensional porphyrin heterostructures in water.