Gregory J. Halder

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The impact of modest, industrially accessible pressures (0-1.2 GPa) on the structure and porosity of the zeolitic imidazolate framework Zn(2-methylimidazole)(2), ZIF-8, was investigated using in situ powder X-ray diffraction in combination with sorption measurements for pressure-treated samples. The framework is highly compressible, with a bulk modulus (K =(More)
The nanoporous metal-organic framework Fe2(azpy)4(NCS)4.(guest) (azpy is trans-4,4'-azopyridine) displays reversible uptake and release of guest molecules and contains electronic switching centers that are sensitive to the nature of the sorbed guests. The switching of this material arises from the presence of iron(II) spin crossover centers within the(More)
Bottoms up! A discrete metallo-supramolecular nanoball (see picture), synthesized by using "bottom-up" methodologies, uniquely undergoes a solvent-sensitive, physically addressable electronic spin switching. The switching occurs by thermal, light, or solvent perturbation, where importantly it can be switched "on" or "off" by green or red laser irradiation,(More)
The nanoporous metal-organic framework [Fe(pz)Ni(CN)(4)], 1 (where pz is pyrazine), exhibits hysteretic spin-crossover at ambient conditions and is robust to the adsorption and desorption of a wide range of small molecular guests, both gases (N(2), O(2), CO(2)) and vapors (methanol, ethanol, acetone, acetonitrile, and toluene). Through the comprehensive(More)
The subtle flexibility of the framework material Co(bpy)1.5(NO3)2.(guest) (bpy = 4,4'-bipyridine) (1.(guest)) is demonstrated quantitatively through in situ single-crystal X-ray diffraction measurements of guest desorption and sorption processes. Variable temperature unit cell determinations were employed to monitor the uptake and release of guest species,(More)
The release of guest species from within a nanoporous metal-organic framework (MOF) has been inhibited by amorphization of the guest-loaded framework structure under applied pressure. Thermogravimetric analyses have shown that by amorphizing ZIF-8 following sorption of molecular I(2), a hazardous radiological byproduct of nuclear energy production, the pore(More)
Systematic exploration of the molecular framework material Zn(CN)2 at high pressure has revealed several distinct series of transitions leading to five new phases: four crystalline and one amorphous. The structures of the new crystalline phases have been resolved through ab initio structural determination, combining charge flipping and direct space methods,(More)