Stuart R. Miller

Biodegradable therapeutic MOFs for the delivery of bioactive molecules

A new metal organic framework (MOF) built up from non-toxic iron and the therapeutically active linker nicotinic acid, with pellagra-curative, vasodilating, and antilipemic properties, has been isolated and characterised via single crystal methods. The release of the therapeutic agent, which is a constituent of the framework, is achieved through the degradation of the hybrid phase, under simulated physiological conditions, allowing for the delivery of the bioactive molecule.

An evaluation of UiO-66 for gas-based applications.

In addition to its high thermal stability, repetitive hydration/dehydration tests have revealed that the porous zirconium terephthalate UiO-66 switches reversibly between its dehydroxylated and hydroxylated versions. The structure of its dehydroxylated form has thus been elucidated by coupling molecular simulations and X-ray powder diffraction data. Infrared measurements have shown that relatively weak acid sites are available while microcalorimetry combined with Monte Carlo simulations emphasize moderate interactions between the UiO-66 surface and a wide range of guest molecules including CH(4), CO, and CO(2). These properties, in conjunction with its significant adsorption capacity, make UiO-66 of interest for its further evaluation for CO(2) recovery in industrial applications. This global approach suggests a strategy for the evaluation of metal-organic frameworks for gas-based applications.

In situ energy-dispersive X-ray diffraction for the synthesis optimization and scale-up of the porous zirconium terephthalate UiO-66.

The synthesis optimization and scale-up of the benchmarked microporous zirconium terephthalate UiO-66(Zr) were investigated by evaluating the impact of several parameters (zirconium precursors, acidic conditions, addition of water, and temperature) over the kinetics of crystallization by time-resolved in situ energy-dispersive X-ray diffraction. Both the addition of hydrochloric acid and water were found to speed up the reaction. The use of the less acidic ZrOCl2·8H2O as the precursor seemed to be a suitable alternative to ZrCl4·xH2O, avoiding possible reproducibility issues as a consequence of the high hygroscopic character of ZrCl4. ZrOCl2·8H2O allowed the formation of smaller good quality UiO-66(Zr) submicronic particles, paving the way for their use within the nanotechnology domain, in addition to higher reaction yields, which makes this synthesis route suitable for the preparation of UiO-66(Zr) at a larger scale. In a final step, UiO-66(Zr) was prepared using conventional reflux conditions at the 0.5 kg scale, leading to a rather high space-time yield of 490 kg m(-3) day(-1), while keeping physicochemical properties similar to those obtained from smaller scale solvothermally prepared batches.

Single Crystal X-ray Diffraction Studies of Carbon Dioxide and Fuel-Related Gases Adsorbed on the Small Pore Scandium Terephthalate Metal Organic Framework, Sc2(O2CC6H4CO2)3

The adsorption behavior of the microporous scandium terephthalate Sc2(O2CC6H4CO2)3 for small fuel-related molecules has been measured. The structure shows an adsorption capacity for N2 and CO2 of 6.5 mmol g(-1) and is able to take up straight chain hydrocarbons. The mechanism of adsorption of CO2, CH4, and C2H6 has been determined by single crystal synchrotron X-ray diffraction at approximately 230 K. Adsorption of CO2 at 235 K and 1 bar pressure and H2 at 80 K and 0.25 bar results in each case in a symmetry change from orthorhombic Fddd to monoclinic C2/c through tilts in the terephthalate linkers. CO2 molecules take up different sites in the two symmetrically different channels that result from this symmetry change. The structure remains orthorhombic in 9 bar of CH4 and 5 bar of C2H6, and the adsorption sites are located. CH4 and C2H6 are observed to adopt sites within the channels, and C2H6 is also observed to adopt adsorption sites between phenyl groups in the channel walls, suggesting that the structure is sufficiently flexible to allow diffusion of small molecules between adjacent channels.

Structural Chemistry, Monoclinic-to-Orthorhombic Phase Transition, and CO2 Adsorption Behavior of the Small Pore Scandium Terephthalate, Sc2(O2CC6H4CO2)3, and Its Nitro- And Amino-Functionalized Derivatives

The crystal structure of the small pore scandium terephthalate Sc(2)(O(2)CC(6)H(4)CO(2))(3) (hereafter Sc(2)BDC(3), BDC = 1,4-benzenedicarboxylate) has been investigated as a function of temperature and of functionalization, and its performance as an adsorbent for CO(2) has been examined. The structure of Sc(2)BDC(3) has been followed in vacuo over the temperature range 140 to 523 K by high resolution synchrotron X-ray powder diffraction, revealing a phase change at 225 K from monoclinic C2/c (low temperature) to Fddd (high temperature). The orthorhombic form shows negative thermal expansivity of 2.4 × 10(-5) K(-1): Rietveld analysis shows that this results largely from a decrease in the c axis, which is caused by carboxylate group rotation. (2)H wide-line and MAS NMR of deuterated Sc(2)BDC(3) indicates reorientation of phenyl groups via π flips at temperatures above 298 K. The same framework solid has also been prepared using monofunctionalized terephthalate linkers containing -NH(2) and -NO(2) groups. The structure of Sc(2)(NH(2)-BDC)(3) has been determined by Rietveld analysis of synchrotron powder diffraction at 100 and 298 K and found to be orthorhombic at both temperatures, whereas the structure of Sc(2)(NO(2)-BDC)(3) has been determined by single crystal diffraction at 298 K and Rietveld analysis of synchrotron powder diffraction at 100, 298, 373, and 473 K and is found to be monoclinic at all temperatures. Partial ordering of functional groups is observed in each structure. CO(2) adsorption at 196 and 273 K indicates that whereas Sc(2)BDC(3) has the largest capacity, Sc(2)(NH(2)-BDC)(3) shows the highest uptake at low partial pressure because of strong -NH(2)···CO(2) interactions. Remarkably, Sc(2)(NO(2)-BDC)(3) adsorbs 2.6 mmol CO(2) g(-1) at 196 K (P/P(0) = 0.5), suggesting that the -NO(2) groups are able to rotate to allow CO(2) molecules to diffuse along the narrow channels.

A Zn azelate MOF: combining antibacterial effect

A novel biocompatible and bioactive Metal–Organic Framework (BioMOF), named BioMIL-5 (Bioactive Materials from Institut Lavoisier), was hydrothermally synthesized from a Zn2+ salt and azelaic acid, both with interesting antibacterial and dermatological properties. Its structure was determined by high resolution X-ray powder diffraction, and further characterized by infrared spectroscopy, thermogravimetric analysis and elemental analysis. The determination of the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of BioMIL-5 in Staphylococcus aureus and Staphylococcus epidermidis demonstrated that the antimicrobial activity of the individual components of BioMIL-5 were maintained after its synthesis. Moreover, BioMIL-5 was found to be stable in water and in bacterial culture medium, especially in water, leading to the subsequent progressive release of its active constituents, AzA and Zn2+ ions. Interestingly, this slow active delivery allowed control of the growth of a S. epidermidis suspension over 7 days. The high stability of this material and the maintenance of its antibacterial properties make BioMIL-5 a good candidate for future bioapplications, for skin care and in cosmetics.

Small chemical causes drastic structural effects: the case of calcium glutarate

A microporous calcium dicarboxylate material, denoted as BioMIL-2 (BioMIL stands for Bioactive Materials from Institut Lavoisier) has been obtained under solvothermal conditions. The material, composed of calcium, a non-toxic and therapeutic element, and the experimental drug glutaric acid, exhibits an unusual, reversible hydration/dehydration behaviour with a transition from a 3-dimensional porous inorganic network to a 1-dimensional inorganic sub-network dense phase upon hydration. The structures of the dehydrated and hydrated materials have been determined via single crystals and powder diffraction analysis, respectively. BioMIL-2 or CaO4C5H6 is a novel microporous material and crystallises in a rhombohedral setting (a = 20.66(1)A, c = 8.64(1)A, V = 3192.4(15)A3, space group: R), within which helical chains of edge-sharing 7 coordinate calcium polyhedra are linked together in order to form a 3-dimensional network with a 1-dimensional pore system. The pores are inaccessible to N2 as they are lined with the carbon atoms of the glutaric acid moiety. Upon hydration, the calcium helicals are separated, yielding a 3-dimensional, non-porous, chained known structure. The hydrated material, BioMIL-2-hyd (CaO4OH2C5H6), crystallises in an orthorhombic setting (a = 6.78(1)A, b = 18.42(1)A, c = 5.87(1)A, V = 733.04(2)A3 space group: P212121) with the structure built up from seven-coordinate dual-capped bipentagonal calcium polyhedra arranged into chains which are connected to each other viaglutarate anions creating a 3-dimensional hybrid structure. The thermal behaviour of BioMIL-2 has been investigated using thermogravimetric analysis and thermodiffractometry and shows a complete reversible hydration/dehydration behaviour without compromise to the structure and a thermal stability up to 573 K. The controlled addition of water to CaO4OH2C5H6 leads to a ‘butter-fly’ like transformation of the framework, from the 3-dimensional inorganic network BioMIL-2 back to the 1-dimensional inorganic sub-network phase.

PST‐1: A Synthetic Small‐Pore Zeolite that Selectively Adsorbs H2

Angewandte Chemie, International Edition 2009, 48, 6647-6649. Includes supplementary information. This is the pre-peer reviewed version of the following article: FULL CITE, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/anie.200903336/full

Synthesis and structure of the framework scandium methylphosphonates ScF(H2O)CH3PO3 and NaSc(CH3PO3)2·0.5H2O

Two framework scandium methylphosphonates have been prepared hydrothermally and their structures solved. ScF(H(2)O)CH(3)PO(3) is a non-porous solid built up from -ScF- chains linked by methylphosphonate groups. The ScO(4)F(2) octahedra are completed by a coordinated water molecule. NaSc(CH(3)PO(3))(2).0.5H(2)O was solved ab initio from high-resolution synchrotron X-ray powder diffraction data. It has a fully connected, negatively charged scandium phosphonate framework where ScO(6) octahedra share vertices with PO(3)CH(3) groups. The solid contains charge balancing sodium cations, coordinated by a water molecule, which may be reversibly removed and adsorbed. The structure of the perdeuterated, dehydrated solid has been refined against neutron powder diffraction data collected at 2.5 K, showing the CD(3) groups in a fully staggered orientation with respect to the phosphonate oxygen atoms.