Enhancing Pore-Environment Complexity Using a Trapezoidal Linker: Toward Stepwise Assembly of Multivariate Quinary Metal–Organic Frameworks

Multicomponent
metal–organic frameworks (MOFs) promise the
precise placement of synergistic functional groups with atomic-level
precision, capable of promoting fascinating developments in basic
sciences and applications. However, the complexity of multicomponent
systems poses a challenge to their structural
design and synthesis. Herein, we show that linkers of low symmetry
can bring new opportunities to the construction of multicomponent
MOFs. A carbazole-tetracarboxylate linker of Cs point group symmetry was designed and
combined with an 8-connected Zr6 cluster to generate a
low-symmetry MOF, PCN-609. PCN-609 contains coordinatively unsaturated
Zr sites arranged within a lattice with three crystallographically
distinct pockets, which can accommodate linear linkers of different
lengths. Sequential linker installation was carried out to postsynthetically
insert three linear linkers into PCN-609, giving rise to a quinary
MOF. Functionalization of each linker from the quinary MOF system
creates multivariate pore environments with unprecedented complexity.