Efficient identification of hydrophobic MOFs: Application in the capture of toxic industrial chemicals

A novel and quick computational strategy is developed based on water Henry's constants to distinguish different levels of hydrophobicity among metal–organic frameworks. The technique is applied to a large database of MOFs to identify hydrophobic materials.We thank the Army Research Office (grant W911NF-12-1-0130) and the EPSRC IAA Partnership Development Award (RG/75759) for financial support. Computational work was partly supported by Northwestern University's shared computer system, Quest (project: P20261). D. F.-J. thanks the Royal Society for funding through a University Research Fellowship. We also thank Prof. Omar Yaghi and Dr Hiroyasu Furukawa for supplying the experimental water isotherms for some of the MOFs studied in this work. We thank Dr Pritha Ghosh and Dr Diego A. Gomez-Gualdron for fruitful discussions.This is the author accepted manuscript. The final version is available from the Royal Society of Chemistry via http://dx.doi.org/10.1039/c5ta06472

Mechanically and chemically robust ZIF-8 monoliths with high volumetric adsorption capacity

The resultant monoliths are mechanically robust structures and present up to 3 times higher volumetric adsorption capacities than the conventional, powder MOF.This work was funded by the EPSRC IAA Partnership Development Award (RG/75759). D.F.-J. thanks the Royal Society for funding through a University Research Fellowship. T.D.B would like to thank Trinity Hall for funding and Professor Anthony Cheetham for use of lab facilities and equipmentThis is the accepted manuscript of a paper published in the Journal of Materials Chemistry A (Tian T, Velazquez-Garcia J, Bennett TD, Fairen-Jimenez D, Journal of Materials Chemistry A, 2015, 3, 2999-3005, doi:10.1039/c4ta05116e). The final version is available at http://dx.doi.org/10.1039/c4ta05116e

A mechanochemical strategy for IRMOF assembly based on pre-designed oxo-zinc precursors.

We demonstrate a mechanochemical strategy that allowed the first successful mechanosynthesis of IRMOFs based on an oxo-centred secondary building unit (SBU). The presented study indicates that controlling the acid-base relationship between reagents is key to mechanochemical synthesis of IRMOFs, revealing a pre-assembled oxo-zinc amidate cluster as an efficient precursor for IRMOF mechanosynthesis.The authors would like to acknowledge the project operated within the Foundation for Polish Science Team Programme co-financed by the EU ‘‘European Regional Development Fund’’ TEAM/2011–7/8, and the European Union in the framework of Regional Development Fund through the Joint UW and WUT International PhD Program of Foundation for Polish Science – “Towards Advanced Functional Materials and Novel Devices” (MPD/2010/4) (D.P.) for financial support.This is the accepted manuscript. The final version was published in Chemical Communications and is available at http://pubs.rsc.org/en/Content/ArticleLanding/2015/CC/c4cc09917f#!divAbstract

Drug delivery and controlled release from biocompatible metal-organic frameworks using mechanical amorphization

We have used a family of Zr-based metal-organic frameworks (MOFs) with different functionalized (bromo, nitro and amino) and extended linkers for drug delivery. We loaded the materials with the fluorescent model molecule calcein and the anticancer drug α-cyano-4-hydroxycinnamic acid (α-CHC), and consequently performed a mechanical amorphization process to attempt to control the delivery of guest molecules. Our analysis revealed that the loading values of both molecules were higher for the MOFs containing unfunctionalized linkers. Confocal microscopy showed that all the materials were able to penetrate into cells, and the therapeutic effect of α-CHC on HeLa cells was enhanced when loaded (20 wt%) into the MOF with the longest linker. On one hand, calcein release required up to 3 days from the crystalline form for all the materials. On the other hand, the amorphous counterparts containing the bromo and nitro functional groups released only a fraction of the total loaded amount, and in the case of the amino-MOF a slow and progressive release was successfully achieved for 15 days. In the case of the materials loaded with α-CHC, no difference was observed between the crystalline and amorphous form of the materials. These results highlight the necessity of a balance between the pore size of the materials and the size of the guest molecules to accomplish a successful and efficient sustained release using this mechanical ball-milling process. Additionally, the endocytic pathway used by cells to internalize these MOFs may lead to diverse final cellular locations and consequently, different therapeutic effects. Understanding these cellular mechanisms will drive the design of more effective MOFs for drug delivery applications.C.A.O. thanks Becas Chile and the Cambridge Trust for funding. D.F.J. thanks the Royal Society (UK) for funding through a University Research Fellowship. RSF thanks the Royal Society for receipt of a University Research Fellowship and the EPSRC (EP/L004461/1) and The University of Glasgow for funding. A.K.C is grateful to the European Research Council for an Advanced Investigator Award

Graphene-wrapped sulfur/metal organic framework-derived microporous carbon composite for lithium sulfur batteries

A three-dimensional hierarchical sandwich-type graphene sheet-sulfur/carbon (GS-S/CZIF8-D) composite for use in a cathode for a lithium sulfur (Li-S) battery has been prepared by an ultrasonic method. The microporous carbon host was prepared by a one-step pyrolysis of Zeolitic Imidazolate Framework-8 (ZIF-8), a typical zinc-containing metal organic framework (MOF), which offers a tunable porous structure into which electro-active sulfur can be diffused. The thin graphene sheet, wrapped around the sulfur/zeolitic imidazolate framework-8 derived carbon (S/CZIF8-D) composite, has excellent electrical conductivity and mechanical flexibility, thus facilitating rapid electron transport and accommodating the changes in volume of the sulfur electrode. Compared with the S/CZIF8-D sample, Li-S batteries with the GS-S/CZIF8-D composite cathode showed enhanced capacity, improved electrochemical stability, and relatively high columbic efficiency by taking advantage of the synergistic effects of the microporous carbon from ZIF-8 and a highly interconnected graphene network. Our results demonstrate that a porous MOF-derived scaffold with a wrapped graphene conductive network structure is a potentially efficient design for a battery electrode that can meet the challenge arising from low conductivity and volume change.National Science Foundation of China (21373028)This is the final version of the article. It first appeared from American Institute of Physics Publishing via http://dx.doi.org/10.1063/1.490175

Amorphous metal-organic frameworks for drug delivery.

We report the encapsulation of the hydrophilic model molecule calcein in the Zr-based MOF UiO-66, followed by amorphization of the framework by ball-milling. We show controlled release of calcein over more than 30 days, compared with the 2 day release period from crystalline UiO-66.C.A.O. thanks Becas Chile and the Cambridge Trust for funding. T.D.B. thanks Trinity Hall (University of Cambridge) for funding. D.F.-J. thanks the Royal Society (UK) for funding through a University Research Fellowship. A.K.C is grateful to the European Research Council for an Advanced Investigator Award.This is the author accepted manuscript. The final version is available from the Royal Society of Chemistry at http://dx.doi.org/10.1039/C5CC05237

Structure-directing factors when introducing hydrogen bond functionality to metal?organic frameworks

The introduction of H-bond donor/acceptor functionality into metal-organic frameworks (MOFs) can have a beneficial effect on their molecular recognition, uptake selectivity and catalytic properties. The changes in ligand geometry induced by incorporation of functional groups may also affect the topology and composition of the resultant MOFs. Herein, we present a comprehensive study of functional group incorporation into MOFs, linked by either Zn2+ paddlewheel units or monomeric Zn2+ corners, which exhibit pcu and dia topology, respectively. Crystallographic analysis shows that amide groups can be easily incorporated into isoreticular pcu pillared-MOFs, whilst integration of urea units results in materials with dia topology. Molecular simulations allow the examination of hypothetical structures with differing constitutions and topologies, and highlight the influence of the urea units in generating the experimentally observed topologies. Noncovalent interactions between independent nets may be significant structure-directing influences, a finding which has great implications for the design of MOFs containing more complex functional groupsFil: Forgan, Ross S.. University Of Glasgow; Reino UnidoFil: Marshall, Ross J.. University Of Glasgow; Reino UnidoFil: Struckmann, Mona. University Of Glasgow; Reino UnidoFil: Bleine, Aurore B.. University Of Glasgow; Reino UnidoFil: Long, De Liang. University Of Glasgow; Reino UnidoFil: Bernini, Maria Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Fairen Jimenez, D.. University of Cambridge; Reino Unid

Investigation of the terahertz vibrational modes of ZIF-8 and ZIF-90 with terahertz time-domain spectroscopy.

We present experimental and computational evidence that gate-opening modes for zeolitic imidazole frameworks can be observed at terahertz frequencies. Our work highlights the critical importance to correctly optimise the crystal structure prior to computational lattice dynamics analysis. The results support the hypothesis that the low energy vibrational modes do indeed play a significant role in host-guest interactions for ZIFs, such as gas loading.C.O.T. thanks Becas Chile and the Cambridge Trust for funding; D.F.-J. thanks the Royal Society (U.K.) for funding through a University Research Fellowship. T.M.K. would like to acknowledge the Royal Society as well as the Royal Society of Chemistry for support.This is the accepted manuscript. The final version is available at via http://dx.doi.org/10.1039/C5CC06455

Metal-Organic Nanosheets Formed via Defect-Mediated Transformation of a Hafnium Metal-Organic Framework

We report a hafnium-containing MOF, hcp UiO-67(Hf), which is a ligand-deficient layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its lower ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed “double cluster” (Hf12O8(OH)14), analogous to the condensation of coordination polyhedra in oxide frameworks. In oxide frameworks, variable stoichiometry can lead to more complex defect structures, e.g., crystallographic shear planes or modules with differing compositions, which can be the source of further chemical reactivity; likewise, the layered hcp UiO-67 can react further to reversibly form a two-dimensional metal–organic framework, hxl UiO-67. Both three-dimensional hcp UiO-67 and two-dimensional hxl UiO-67 can be delaminated to form metal–organic nanosheets. Delamination of hcp UiO-67 occurs through the cleavage of strong hafnium-carboxylate bonds and is effected under mild conditions, suggesting that defect-ordered MOFs could be a productive route to porous two-dimensional materials

Discovery of an Optimal Porous Crystalline Material for the Capture of Chemical Warfare Agents

Chemical warfare agents (CWAs) are regarded as a critical challenge in our society. Here, we use a high-throughput computational screening strategy backed up by experimental validation to identify and synthesize a promising porous material for CWA removal under humid conditions. Starting with a database of 2,932 existing metal-organic framework (MOF) structures, we selected those possessing cavities big enough to adsorb well-known CWAs such as sarin, soman, and mustard gas as well as their nontoxic simulants. We used Widom method to reduce significantly the simulation time of water adsorption, allowing us to shortlist 156 hydrophobic MOFs where water will not compete with the CWAs to get adsorbed. We then moved to grand canonical Monte Carlo (GCMC) simulations to assess the removal capacity of CWAs. We selected the best candidates in terms of performance but also in terms of chemical stability and moved to synthesis and experimental breakthrough adsorption to probe the predicted, excellent performance. This computational-experimental work represents a fast and efficient approach to screen porous materials in applications that involve the presence of moisture