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Cameron J. Kepert

Bio: Cameron J. Kepert is an academic researcher from University of Sydney. The author has contributed to research in topics: Spin crossover & Negative thermal expansion. The author has an hindex of 59, co-authored 197 publications receiving 12769 citations. Previous affiliations of Cameron J. Kepert include University of Cambridge & University of Queensland.


Papers
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Journal ArticleDOI
29 Nov 2002-Science
TL;DR: The generation of a host lattice that interacts with exchangeable guest species in a switchable fashion has implications for the generation of previously undeveloped advanced materials with applications in areas such as molecular sensing.
Abstract: 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 framework lattice, the sorbed phases undergoing "half-spin" crossovers, and the desorbed phase showing no switching property. The interpenetrated framework structure displays a considerable flexibility with guest uptake and release, causing substantial changes in the local geometry of the iron(II) centers. The generation of a host lattice that interacts with exchangeable guest species in a switchable fashion has implications for the generation of previously undeveloped advanced materials with applications in areas such as molecular sensing.

1,401 citations

Journal ArticleDOI
TL;DR: In this paper, two families of molecular frameworks which grow as homochiral single crystals are described, which consist of multiple interpenetration of the three-connected chiral (10,3)-a (Y*) network and result from the tridentate coordination of the 1,3,5-benzenetricarboxylate (btc) ligand to octahedral metal centers.
Abstract: Two families of molecular frameworks which grow as homochiral single crystals are described. Both consist of multiple interpenetration of the three-connected chiral (10,3)-a (Y*) network and result from the tridentate coordination of the 1,3,5-benzenetricarboxylate (btc) ligand to octahedral metal centers which act as linear connectors. The nature of the interpenetration is controlled by the auxiliary ligands bound in the equatorial plane of the metal center. Ethylene glycol (eg) binds in a unidentate fashion to form phase A which has 28% accessible solvent volume and contains four interpenetrating (10,3)-a networks. 1,2-Propanediol (1,2-pd) coordinates as a bidentate ligand to yield a phase B with a greatly enhanced 51% of solvent accessible volume, because only two (distorted) (10,3)-a‘ networks interpenetrate. Ligands in the void space and bound to the metal center can both be liberated thermally: the kinetics of this process allow isolation of microporous desolvated crystalline A and B. The porous ph...

564 citations

Journal ArticleDOI
TL;DR: A number of areas where specific function has been incorporated into framework host lattices for their extreme chemical versatility are highlighted.

412 citations

Journal ArticleDOI
TL;DR: Through the comprehensive analysis of structure, host-guest properties, and spin-crossover behaviors, it is found that this pillared Hofmann system uniquely displays both guest-exchange-induced changes to spin- crossovers and spinsorption and desorption changes to host- Guernsey properties, with direct dynamic interplay between these two phenomena.
Abstract: 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 (N2, O2, CO2) and vapors (methanol, ethanol, acetone, acetonitrile, and toluene). Through the comprehensive analysis of structure, host−guest properties, and spin-crossover behaviors, it is found that this pillared Hofmann system uniquely displays both guest-exchange-induced changes to spin-crossover and spin-crossover-induced changes to host−guest properties, with direct dynamic interplay between these two phenomena. Guest desorption and adsorption cause pronounced changes to the spin-crossover behavior according to a systematic trend in which larger guests stabilize the high-spin state and therefore depress the spin-crossover temperature of the host lattice. When stabilizing the alternate spin state of the host at any given temperature, these processes directly stimul...

391 citations

Journal ArticleDOI
TL;DR: In this paper, the intrinsic geometric flexibility of framework structures incorporating linear metal-cyanide-consuming linkages using a reciprocal-space dynamical matrix approach was analyzed, and it was shown that this structural motif is capable of imparting a significant negative thermal expansion sNTEd effect upon such materials.
Abstract: We analyze the intrinsic geometric flexibility of framework structures incorporating linear metal–cyanide– metal sM–CN–M8d linkages using a reciprocal-space dynamical matrix approach. We find that this structural motif is capable of imparting a significant negative thermal expansion sNTEd effect upon such materials. In particular, we show that the topologies of a number of simple cyanide-containing framework materials support a very large number of low-energy rigid-unit phonon modes, all of which give rise to NTE behavior. We support our analysis by presenting experimental verification of this behavior in the family of compounds ZnxCd1−xsCNd2, which we show to exhibit a NTE effect over the temperature range 25–375 K more than double that of materials such as ZrW2O8.

302 citations


Cited by
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Journal ArticleDOI
30 Aug 2013-Science
TL;DR: Metal-organic frameworks are porous materials that have potential for applications such as gas storage and separation, as well as catalysis, and methods are being developed for making nanocrystals and supercrystals of MOFs for their incorporation into devices.
Abstract: Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

10,934 citations

Journal ArticleDOI
10 Mar 1970

8,159 citations

Journal ArticleDOI
12 Jun 2003-Nature
TL;DR: This work has shown that highly porous frameworks held together by strong metal–oxygen–carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.
Abstract: The long-standing challenge of designing and constructing new crystalline solid-state materials from molecular building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: we call this approach reticular synthesis. This chemistry has yielded materials designed to have predetermined structures, compositions and properties. In particular, highly porous frameworks held together by strong metal-oxygen-carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.

8,013 citations

Journal ArticleDOI
TL;DR: This critical review starts with a brief introduction to gas separation and purification based on selective adsorption, followed by a review of gas selective adsorbents in rigid and flexible MOFs, and primary relationships between adsorptive properties and framework features are analyzed.
Abstract: Adsorptive separation is very important in industry. Generally, the process uses porous solid materials such as zeolites, activated carbons, or silica gels as adsorbents. With an ever increasing need for a more efficient, energy-saving, and environmentally benign procedure for gas separation, adsorbents with tailored structures and tunable surface properties must be found. Metal–organic frameworks (MOFs), constructed by metal-containing nodes connected by organic bridges, are such a new type of porous materials. They are promising candidates as adsorbents for gas separations due to their large surface areas, adjustable pore sizes and controllable properties, as well as acceptable thermal stability. This critical review starts with a brief introduction to gas separation and purification based on selective adsorption, followed by a review of gas selective adsorption in rigid and flexible MOFs. Based on possible mechanisms, selective adsorptions observed in MOFs are classified, and primary relationships between adsorption properties and framework features are analyzed. As a specific example of tailor-made MOFs, mesh-adjustable molecular sieves are emphasized and the underlying working mechanism elucidated. In addition to the experimental aspect, theoretical investigations from adsorption equilibrium to diffusion dynamics via molecular simulations are also briefly reviewed. Furthermore, gas separations in MOFs, including the molecular sieving effect, kinetic separation, the quantum sieving effect for H2/D2 separation, and MOF-based membranes are also summarized (227 references).

7,186 citations

Journal ArticleDOI
18 Nov 1999-Nature
TL;DR: In this article, an organic dicarboxylate linker is used in a reaction that gives supertetrahedron clusters when capped with monocarboxyates.
Abstract: Open metal–organic frameworks are widely regarded as promising materials for applications1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 in catalysis, separation, gas storage and molecular recognition. Compared to conventionally used microporous inorganic materials such as zeolites, these organic structures have the potential for more flexible rational design, through control of the architecture and functionalization of the pores. So far, the inability of these open frameworks to support permanent porosity and to avoid collapsing in the absence of guest molecules, such as solvents, has hindered further progress in the field14,15. Here we report the synthesis of a metal–organic framework which remains crystalline, as evidenced by X-ray single-crystal analyses, and stable when fully desolvated and when heated up to 300?°C. This synthesis is achieved by borrowing ideas from metal carboxylate cluster chemistry, where an organic dicarboxylate linker is used in a reaction that gives supertetrahedron clusters when capped with monocarboxylates. The rigid and divergent character of the added linker allows the articulation of the clusters into a three-dimensional framework resulting in a structure with higher apparent surface area and pore volume than most porous crystalline zeolites. This simple and potentially universal design strategy is currently being pursued in the synthesis of new phases and composites, and for gas-storage applications.

6,778 citations