In the past decades, many attempts
have been made to mimic the
energy transfer (EnT) in photosynthesis, a key process occurring in
nature that is of fundamental significance in solar fuels and sustainable
energy. Metal–organic frameworks (MOFs), an emerging class
of porous crystalline materials self-assembled from organic linkers
and metal or metal cluster nodes, offer an ideal platform for the
exploration of directional EnT phenomena. However, placing energy
donor and acceptor moieties within the same framework with an atomistic
precision appears to be a major synthesis challenge. In this work,
we report the design and synthesis of a highly porous and photoactive N,N′-bicarbazole- and porphyrin-based mixed-ligand
MOF, namely, NPF-500-H2TCPP (NPF = Nebraska porous framework;
H2TCPP = meso-tetrakis(4-carboxyphenyl)porphyrin),
where the secondary ligand H2TCPP is incorporated precisely
through the open metal sites of the equatorial plane of the octahedron
cage resulting from the underlying (4,8) connected network of NPF-500.
The efficient EnT process from N,N′-bicarbazole
to porphyrin in NPF-500-H2TCPP was captured by time-resolved
spectroscopy and exemplified by photocatalytic oxidation of thioanisole.
These results demonstrate not only the capability of NPF-500 as the
scaffold to precisely arrange the donor–acceptor assembly for
the EnT process but also the potential to directly utilize the EnT
process for photocatalytic applications.