Showing papers by "Kyle E. Cordova published in 2016"

A Titanium–Organic Framework as an Exemplar of Combining the Chemistry of Metal– and Covalent–Organic Frameworks

Abstract: A crystalline material with a two-dimensional structure, termed metal–organic framework-901 (MOF-901), was prepared using a strategy that combines the chemistry of MOFs and covalent–organic frameworks (COFs). This strategy involves in situ generation of an amine-functionalized titanium oxo cluster, Ti6O6(OCH3)6(AB)6 (AB = 4-aminobenzoate), which was linked with benzene-1,4-dialdehyde using imine condensation reactions, typical of COFs. The crystal structure of MOF-901 is composed of hexagonal porous layers that are likely stacked in staggered conformation (hxl topology). This MOF represents the first example of combining metal cluster chemistry with dynamic organic covalent bond formation to give a new crystalline, extended framework of titanium metal, which is rarely used in MOFs. The incorporation of Ti(IV) units made MOF-901 useful in the photocatalyzed polymerization of methyl methacrylate (MMA). The resulting polyMMA product was obtained with a high-number-average molar mass (26 850 g mol–1) and low ...

High proton conductivity at low relative humidity in an anionic Fe-based metal–organic framework

Abstract: A metal–organic framework, termed VNU-15 (VNU = Vietnam National University), was synthesized and subsequent detailed structural analysis revealed that the crystalline structure adopted the fob topology. Due to integrated sulphate ligands accompanied by hydrogen-bonded dimethylammonium ions that lined the pore channels of VNU-15, the proton conductivity of this material reached 2.90 × 10−2 S cm−1 at 95 °C and 60% relative humidity. Remarkably, the high proton conductivity of VNU-15 was maintained under these conditions, without any appreciable loss, for 40 h.

High Methanol Uptake Capacity in Two New Series of Metal–Organic Frameworks: Promising Materials for Adsorption-Driven Heat Pump Applications

Abstract: Two new series of metal–organic frameworks (MOFs), termed M-VNU-74-I and -II (where M = Mg, Ni, Co; VNU = Vietnam National University) were designed to expand the methanol uptake capacities with polar amide functionalities. The resulting MOFs, isoreticular to MOF-74, exhibited high porosity (up to 3000 m2 g–1) as well as the highest reported methanol uptake [>1 g g–1 or >400 cm3 cm–3]. As a representative example, Mg-VNU-74-II was shown to maintain a remarkably high stability and methanol mass transfer capacity for at least 42 ad/desorption cycles (3 days). Indeed, these findings highlight the potential of such materials for practical use in adsorption heat pump applications.

Mixed-Metal Zeolitic Imidazolate Frameworks and their Selective Capture of Wet Carbon Dioxide over Methane.

Abstract: A presynthesized, square planar copper imidazole complex, [Cu(imidazole)4](NO3)2, was utilized as a precursor in the synthesis of a new series of zeolitic imidazolate frameworks, termed ZIF-202, -203, and -204. The structures of all three members were solved by single-crystal X-ray diffraction analysis, which revealed ZIF-203 and -204 having successfully integrated square planar units within the backbones of their respective frameworks. As a result of this unit, the structures of both ZIF-203 and -204 were found to adopt unprecedented three-dimensional nets, namely, ntn and thl, respectively. One member of this series, ZIF-204, was demonstrated to be highly porous, exhibit exceptional stability in water, and selectively capture CO2 over CH4 under both dry and wet conditions without any loss in performance over three cycles. Remarkably, the regeneration of ZIF-204 was performed under the mild conditions of flowing a pure N2 gas through the material at ambient temperature.

Metal Organic Frameworks as Emerging Photocatalysts

Abstract: Increasing number of metal-organic frameworks (MOFs) have recently been recognised as a new generation of emerging porous photocatalysts in photocatalysis and photoelectrocatalysis, since their intrinsic coordination structure between the metal cluster and organic ligands offers MOFs great flexibility to tune their semiconducting property for enhanced light harvesting. In order to improve their performance substantially and achieve widespread application of MOF photocatalysts, it is necessary to develop effective synthesis strategies and understand their semiconducting crystal structure, photocatalytic mechanism in depth. This chapter firstly provides a brief introduction of the MOF materials; this chapter addresses the crystallinity, porosity and electronic semiconducting structures that are essential in solar energy conversion. Established and innovative syntheses strategies of MOFs are then categorised and illustrated, followed by various characterisations techniques applied to investigate their structural and semiconducting properties (band structure and charge transfer), including X-ray Diffraction XRD, small angle X-ray Diffraction SAXRD, adsorption/desorption, UV-Vis, nuclear magnetic resonance (NMR), extended fine Auger structures (EXFAS), inelastic neutron scattering (INS) spectroscopy, high-resolution transmission electron microscopy (HR)TEM and electrochemical measurements. The photocatalytic and photoelectrocatalytic application of MOFs are introduced addressing their unique photocatalytic mechanism. The perspectives of MOF photocatalysts are finally presented to encourage the future development. The content of this chapter suits the users including beginners, postgraduates and professionals.