Molecular Assembly of Functional Motifs for Artificial Photosynthesis

Natural photosynthesis has produced most of the energy that fuels human society and sustains life on earth. However, with an ever-growing demand for energy, urgent efforts are required to develop artificial systems that mimic the essential processes of natural photosynthesis, including light harvesting/charge separation, photocatalytic water oxidation, energy storage, and catalytic CO₂ reduction. Recent advancements have seen the development of nanoscale photoelectrochemical materials that integrate light absorbers with cocatalysts or redox units for artificial photosynthetic systems. However, the potential of molecular photoelectrochemical materials, which couple electron donor–acceptor (D-A) structures with catalytic or redox-active moieties into a periodic porous aggregate, remains largely underexplored. By combining D–A structures with redox moieties, these materials can enable solar-to-electrochemical energy storage process, while the further incorporation of catalytic sites can extend their application to photo(electro)catalytic water oxidation or CO₂ reduction, thus enabling customized artificial systems. On the other hand, they can enhance energy efficiency by molecular-scale in situ photogenerated charge separation coupled with redox reactions─an exciton-involved redox mechanism─to circumvent the energy losses typically associated with charge carrier transport in nanoscale counterparts. Despite these merits, critical challenges remain with a limited understanding of the structure–functional motif relationship at the molecular level and a shortage of molecular assemblies to enable multifunctional motifs necessary for overall natural photosynthesis mimicry.