Probing Structural Defects in MOFs Using Water Stability

Defects in the crystal
structures of metal–organic frameworks
(MOFs), whether present intrinsically or introduced via so-called
defect engineering, can play strong roles in the properties of MOFs
for various applications. Unfortunately, direct experimental detection
and characterization of defects in MOFs are very challenging. We show
that in many cases, the differences between experimentally observed
and computationally predicted water stabilities of MOFs can be used
to deduce information on the presence of point defects in real materials.
Most computational studies of MOFs consider these materials to be
defect-free, and in many cases, the resulting structures are predicted
to be hydrophobic. Systematic experimental studies, however, have
shown that many MOFs are hydrophilic. We show that the existence of
chemically plausible point defects can often account for this discrepancy
and use this observation in combination with detailed molecular simulations
to assess the impact of local defects and flexibility in a variety
of MOFs for which defects had not been considered previously.