1 research outputs found
Anharmonic Origin of Giant Thermal Displacements in the Metal–Organic Framework UiO-67
The
crystallography of mechanically soft materials such as hybrid
organic–inorganic compounds often reveals large thermal displacement
factors and partially occupied lattice sites, which can arise from
static or dynamic disorder. A combination of <i>ab initio</i> lattice dynamics and molecular dynamics simulations reveals the
origin of the giant thermal displacements in the biphenyl-4,4′-dicarboxylate
(BPDC) linker in the metal–organic framework UiO-67. The dihedral
angle between the two phenyl rings has two equivalent minima at ±31°,
which cannot be described by harmonic phonons. Instead, anharmonic
switching between the minima results in the experimentally observed
large thermal ellipsoids. The switching frequency is found to be similar
in the topologically distinct framework IRMOF-10, suggesting that
dynamic disorder is a general feature of MOFs based on BPDC and structurally
similar linkers