Conspectus
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 reactionsan exciton-involved
redox mechanismto 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.
In this Account, we introduce the general concept of molecular
photoelectrochemical materials for artificial photosynthesis, emphasizing
their structural advantages in enabling diverse functional motifs.
We also outline fundamental design principles and operational mechanisms
of these motifs at the molecular level. Furthermore, we present three
specific cases of molecular assembly targeting different functional
motifs: (1) a donor (photocatalytic water oxidation)–acceptor
(reduction) functional motif for solar-to-chemical conversion; (2)
a donor (oxidation)–acceptor (reduction) motif for solar-to-electrochemical
energy storage; and (3) a donor (oxidation)–acceptor (photocatalytic
CO2 reduction) motif for solar-to-electrochemical energy
storage and conversion. The essential role of intramolecular photoinduced
PCET during the operation of each functional motif is also discussed.
Finally, we conclude with an overview of major challenges and future
prospects for modulating molecular assemblies to achieve high energy
conversion efficiency, along with a perspective on the design of versatile
molecular materials and the implementation of photoinduced PCET to
couple multifunctional motifs for overall natural photosynthesis mimicry.
We hope that this Account will provide molecular level insight into
the rational design of molecular photoelectrochemica...
