Precisely Embedding Active Sites into a Mesoporous Zr-Framework through Linker Installation for High-Efficiency Photocatalysis

The pore engineering of microporous
metal–organic frameworks
(MOFs) has been extensively investigated in the past two decades,
and an expansive library of functional groups has been introduced
into various frameworks. However, the reliable procurement of MOFs
possessing both a targeted pore size and preferred functionality together
is less common. This is especially important since the applicability
of many elaborately designed materials is often restricted by the
small pore sizes of microporous frameworks. Herein, we designed and
synthesized a mesoporous MOF based on Zr6 clusters and
tetratopic carboxylate ligands, termed PCN-808. The accessible coordinatively
unsaturated metal sites as well as the intrinsic flexibility of the
framework make PCN-808 a prime scaffold for postsynthetic modification
via linker installation. A linear ruthenium-based metalloligand was
successfully and precisely installed into the walls of open channels
in PCN-808 while maintaining the mesoporosity of the framework. The
photocatalytic activity of the obtained material, PCN-808-BDBR, was
examined in the aza-Henry reaction and demonstrated high conversion
yields after six catalytic cycles. Furthermore, thanks to the mesoporous
nature of the framework, PCN-808-BDBR also exhibits exceptional yields
for the photocatalytic oxidation of dihydroartemisinic acid to artemisinin.