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

High-Throughput Screening of Porous Crystalline Materials for Hydrogen Storage Capacity near Room Temperature

The hydrogen storage capabilities of 18,383 porous crystalline structures possessing various degrees of Mg functionalization and diverse physical properties were assessed through combined grand canonical Monte Carlo (GCMC) and quantum mechanical approaches. GCMC simulations were performed for pressures of 2 and 100 bar at a temperature of 243 K. Absolute uptake at 100 bar and deliverable capacity between 100 bar and 2 bar were calculated. Maximum absolute and deliverable gravimetric capacities were 9.35 wt% and 9.12 wt % respectively. Volumetrically, absolute and deliverable capacities were 51 g/L and 30 g/L respectively. In addition, the results reveal relationships between hydrogen uptake and the physical properties of the materials. We show that the introduction of an optimum amount of Mg alkoxide to increase the isosteric heat of adsorption is a promising strategy to improve hydrogen uptake and delivery near ambient temperature.This research was supported by the U.S. Department of Energy (DE-FG02-08EF15967). This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grand No. DGE-0824162 (Y. J. C.). D.F.-J. acknowledges the Royal Society (UK) for a University Research Fellowship. We gratefully acknowledge Northwestern University’s Quest cluster and the National Energy Research Scientific Computing Center’s Carver Cluster for computer resources.This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/jp4122326

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

Trinuclear Cage-Like Zn(II) Macrocyclic Complexes: Enantiomeric Recognition and Gas Adsorption Properties.

Three zinc(II) ions in combination with two units of enantiopure [3+3] triphenolic Schiff-base macrocycles 1, 2, 3, or 4 form cage-like chiral complexes. The formation of these complexes is accompanied by the enantioselective self-recognition of chiral macrocyclic units. The X-ray crystal structures of these trinuclear complexes show hollow metal-organic molecules. In some crystal forms, these barrel-shaped complexes are arranged in a window-to-window fashion, which results in the formation of 1D channels and a combination of both intrinsic and extrinsic porosity. The microporous nature of the [Zn3 12 ] complex is reflected in its N2 , Ar, H2 , and CO2 adsorption properties. The N2 and Ar adsorption isotherms show pressure-gating behavior, which is without precedent for any noncovalent porous material. A comparison of the structures of the [Zn3 12 ] and [Zn3 32 ] complexes with that of the free macrocycle H3 1 reveals a striking structural similarity. In H3 1, two macrocyclic units are stitched together by hydrogen bonds to form a cage very similar to that formed by two macrocyclic units stitched together by Zn(II) ions. This structural similarity is manifested also by the gas adsorption properties of the free H3 1 macrocycle. Recrystallization of [Zn3 12 ] in the presence of racemic 2-butanol resulted in the enantioselective binding of (S)-2-butanol inside the cage through the coordination to one of the Zn(II) ions.This work was supported by the NCN (NarodoweCentrumNauki, Poland) (grant 2011/03/B/ST5/01060).D.P.and J.L.thank the FNP Program“Mistrz” for financial support, and D.F.-J. thanks the Royal Society for funding through a University Research Fellowship.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/chem.20150347

Selective Surface PEGylation of UiO-66 Nanoparticles for Enhanced Stability, Cell Uptake, and pH-Responsive Drug Delivery.

The high storage capacities and excellent biocompatibilities of metal-organic frameworks (MOFs) have made them emerging candidates as drug-delivery vectors. Incorporation of surface functionality is a route to enhanced properties, and here we report on a surface-modification procedure-click modulation-that controls their size and surface chemistry. The zirconium terephthalate MOF UiO-66 is (1) synthesized as ∼200 nm nanoparticles coated with functionalized modulators, (2) loaded with cargo, and (3) covalently surface modified with poly(ethylene glycol) (PEG) chains through mild bioconjugate reactions. At pH 7.4, the PEG chains endow the MOF with enhanced stability toward phosphates and overcome the "burst release" phenomenon by blocking interaction with the exterior of the nanoparticles, whereas at pH 5.5, stimuli-responsive drug release is achieved. The mode of cellular internalization is also tuned by nanoparticle surface chemistry, such that PEGylated UiO-66 potentially escapes lysosomal degradation through enhanced caveolae-mediated uptake. This makes it a highly promising vector, as demonstrated for dichloroacetic-acid-loaded materials, which exhibit enhanced cytotoxicity. The versatility of the click modulation protocol will allow a wide range of MOFs to be easily surface functionalized for a number of applications

Trinuclear Cage-Like ZnII Macrocyclic Complexes: Enantiomeric Recognition and Gas Adsorption Properties

Three zinc(II) ions in combination with two units of enantiopure 3+3 triphenolic Schiff base macrocycles 1, 2, 3 or 4 form cage-like chiral complexes. The formation of these complexes is accompanied by the enantioselective self-recognition of chiral macrocyclic units. The X-ray crystal structures of these trinuclear complexes show hollow metal-organic molecules. In some crystal forms, these barrel-shaped complexes are arranged in a window-to-window fashion which results in formation of 1-D channels and combination of intrinsic porosity with extrinsic porosity. The microporous nature of the [Zn312] complex is reflected in its N2, Ar, H2 and CO2 adsorption properties. The N2 and Ar adsorption isotherms showed pressure gating behaviour which is without precedent for any noncovalent porous material. The comparison of the structures of the [Zn312] and [Zn332] complexes with that of the free macrocycle H31 reveals a striking structural similarity. In the latter compound two macrocyclic units stitched together by hydrogen bonds form a cage very similar to that formed by two macrocyclic units stitched together by Zn(II) ions. This structural similarity is manifested also by the gas adsorption properties of the free H31 macrocycle. Recrystallization of [Zn312] in the presence of racemic 2-butanol results in enantioselective binding of the (S)-2-butanol inside the cage via coordination to one of Zn(II) ions.This work was supported by the NCN (NarodoweCentrumNauki, Poland) (grant 2011/03/B/ST5/01060).D.P.and J.L.thank the FNP Program“Mistrz” for financial support, and D.F.-J. thanks the Royal Society for funding through a University Research Fellowship.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/chem.20150347

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

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

Role of crystal size on swing-effect and adsorption induced structure transition of ZIF-8.

The flexibility and structure transition behaviour of ZIF-8 in a series of samples with different particle size has been studied using a combination of high-resolution N2 gas adsorption isotherms and, for the first time, a broad in situ PXRD and Rietveld analysis. During the stepped adsorption process, large particles showed a narrow adsorption/desorption pressure range with a shorter equilibrium time due to lower kinetic hindrance, deriving from higher amount of active sites. In situ PXRD showed that both the rotation of imidazole ring and a bend in the methyl group led to the gate opening of ZIF-8.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. We thank Diamond Light Source for beamtime at beamline I11 (visit EE9750).This is the author accepted manuscript. The final version is available from the Royal Society of Chemistry via http://dx.doi.org/10.1039/C6DT00565

A comparison of copper and acid site zeolites for the production of nitric oxide for biomedical applications

The authors would like to thank the Engineering and Physical Sciences Research Council, University of St Andrews, and CRITICAT Centre for Doctoral Training for financial support [Ph.D. studentship to SR; Grant code: EP/L016419/1]. 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. Thanks also go to Chevron for the sample of H-SSZ-13.Copper-exchanged and acidic zeolites are shown to produce nitric oxide (NO) from a nitrite source in biologically active (nanomolar) concentrations. Four zeolites were studied; mordenite, ferrierite, ZSM-5 and SSZ-13, which had varying pore size, channel systems and Si/Al ratios. ZSM-5 and SSZ-13 produced the highest amounts of NO in both the copper and acid form. The high activity and regeneration of the copper active sites makes them good candidates for long-term NO production. Initial cytotoxicity tests have shown at least one of the copper zeolites (Cu-SSZ-13) to be biocompatible, highlighting the potential usage within biomedical applications.PostprintPeer reviewe