Topology-Guided Design and Syntheses of Highly Stable Mesoporous Porphyrinic Zirconium Metal–Organic Frameworks with High Surface Area

Through
a topology-guided strategy, a series of Zr6-containing
isoreticular porphyrinic metal–organic frameworks (MOFs), PCN-228, PCN-229, and PCN-230, with ftw-a topology were synthesized using the extended porphyrinic
linkers. The bulky porphyrin ring ligand effectively prevents the
network interpenetration which often appears in MOFs with increased
linker length. The pore apertures of the structures range from 2.5
to 3.8 nm, and PCN-229 demonstrates the highest porosity
and BET surface area among the previously reported Zr-MOFs. Additionally,
by changing the relative direction of the terminal phenyl rings, this
series replaces a Zr8 cluster with a smaller Zr6 cluster in a topologically identical framework. The high connectivity
of the Zr6 cluster yields frameworks with enhanced stability
despite high porosity and ultralarge linker. As a representative example, PCN-230, constructed with the most extended porphyrinic linker,
shows excellent stability in aqueous solutions with pH values ranging
from 0 to 12 and demonstrates one of the highest pH tolerances among
all porphyrinic MOFs. This work not only presents a successful example
of rational design of MOFs with desired topology, but also provides
a strategy for construction of stable mesoporous MOFs.