Vacancy defect configurations in the metal-organic framework UiO-66: energetics and electronic structure.

Vacancy lattice sites in the metal-organic framework UiO-66 are known to have a profound effect on the material properties. Here we use density functional theory to compare the energies of defect arrangements containing missing linkers and missing metal clusters for different choices of charge compensation. Our results show that the preference for missing metal clusters or missing linker defects depends on the charge compensation as well as the overall concentration of defects in the crystal.

A general forcefield for accurate phonon properties of metal-organic frameworks.

We report the development of a forcefield capable of reproducing accurate lattice dynamics of metal-organic frameworks. Phonon spectra, thermodynamic and mechanical properties, such as free energies, heat capacities and bulk moduli, are calculated using the quasi-harmonic approximation to account for anharmonic behaviour due to thermal expansion. Comparison to density functional theory calculations of properties such as Grüneisen parameters, bulk moduli and thermal expansion supports the accuracy of the derived forcefield model.

Free Energy of Ligand Removal in the Metal-Organic Framework UiO-66.

We report an investigation of the "missing-linker phenomenon" in the Zr-based metal-organic framework UiO-66 using atomistic force field and quantum chemical methods. For a vacant benzene dicarboxylate ligand, the lowest energy charge-capping mechanism involves acetic acid or Cl/HO. The calculated defect free energy of formation is remarkably low, consistent with the high defect concentrations reported experimentally.

Compositional control of pore geometry in multivariate metal-organic frameworks: an experimental and computational study.

A new approach is reported for tailoring the pore geometry in five series of multivariate metal–organic frameworks (MOFs) based on the structure [Zn2(bdc)2(dabco)] (bdc = 1,4-benzenedicarboxylate, dabco = 1,8-diazabicyclooctane), DMOF-1. A doping procedure has been adopted to form series of MOFs containing varying linker ratios. The series under investigation are [Zn2(bdc)(2-x)(bdc-Br)x(dabco)]·nDMF 1 (bdc-Br = 2-bromo-1,4-benzenedicarboxylate), [Zn2(bdc)(2-x)(bdc-I)x(dabco)]·nDMF 2 (bdc-I = 2-iodo-1,4-benzenedicarboxylate), [Zn2(bdc)(2-x)(bdc-NO2)x(dabco)]·nDMF 3 (bdc-NO2 = 2-nitro-1,4-benzenedicarboxylate), [Zn2(bdc)(2-x)(bdc-NH2)x(dabco)]·nDMF 4 (bdc-NH2 = 2-amino-1,4-benzenedicarboxylate) and [Zn2(bdc-Br)(2-x)(bdc-I)x(dabco)]·nDMF 5.

Transferable Force Field for Metal-Organic Frameworks from First-Principles: BTW-FF.

We present an ab-initio derived force field to describe the structural and mechanical properties of metal-organic frameworks (or coordination polymers). The aim is a transferable interatomic potential that can be applied to MOFs regardless of metal or ligand identity. The initial parametrization set includes MOF-5, IRMOF-10, IRMOF-14, UiO-66, UiO-67, and HKUST-1.

Microscopic origin of the optical processes in blue sapphire.

Al2O3 changes from transparent to a range of intense colours depending on the chemical impurities present. In blue sapphire, Fe and Ti are incorporated; however, the chemical process that gives rise to the colour has long been debated. Atomistic modelling identifies charge transfer from Ti(III) to Fe(III) as being responsible for the characteristic blue appearance.