Exploring the Isoreticular Continuum between Phosphonate- and Phosphinate-Based Metal–Organic Frameworks

The rational design of metal–organic frameworks
(MOFs) is
one of the driving forces behind the great success that this class
of materials is experiencing. The so-called isoreticular approach
is a key design tool, very often used to tune the size, steric properties,
and additional functional groups of the linker used. In this work,
we go one step further and show that even linkers with two different
coordinating groups, namely, phosphonate and phosphinate, can form
isoreticular MOFs. This effectively bridges the gap between MOFs utilizing
phosphinate and phosphonate coordinating groups. Using a novel bifunctional
ligand, 4-[hydroxy(methyl)phosphoryl]phenylphosphonic acid [H3PPP(Me)], we were able to prepare ICR-12, a MOF isoreticular
to already published MOFs containing bisphosphinate linkers (e.g.,
ICR-4). An isostructural MOF ICR-13 was also successfully prepared
using 1,4-benzenediphosphonic acid. We envisage that this strategy
can be used to further enlarge the pool of MOFs.