Dr Cameron Keppert
Position: Senior Lecturer, Chemistry
Affiliation: University of Sydney, School of Chemistry
Phone: +61 (02) 9351 5741
Areas of interest:
Microporous Molecular Frameworks: Molecular framework materials are crystalline solids that contain extended networks constructed by the linkage of metal atoms by multiply-coordinating polydentate ligands. A rapid growth in the study of these materials has arisen from the realisation that metal-organic framework synthesis offers considerable flexibility and control over structure and properties, thereby offering rare pathways to rational materials design. This flexibility originates from the enormous structural and chemical diversities afforded by molecular systems, features that are less prevalent in many other branches of materials chemistry.
The recent emergence of microporosity in molecular frameworks has led to widespread speculation that such materials may be ideally suited for applications such as molecular separation, sensing and heterogeneous catalysis. Our primary research efforts are being directed towards exploring these issues, addressing, in particular, whether there are any limitations to this porosity and to what extent the frameworks may be thought of as rigid. Experimentation involves the synthesis of new materials by diffusion-controlled and solvothermal methods, and structural and physical characterisations using techniques that include single crystal and powder X-ray diffraction, vibrational spectroscopy (IR and Raman), TGA/DSC of guest desorption and sorption, NMR, SQUID magnetometry, EPR and theoretical modelling of guest molecule docking and packing.
Chiral Phases: The search for chiral microporous materials, widely regarded as a Holy Grail within solid state chemistry, is driven by the potential application of such materials for chiral separations and enantioselective syntheses. We have recently made significant in-roads into this area by developing a large and diverse array of porous, chiral molecular framework solids, including some that are the only such materials known that can be synthesised homochirally. Experiments show that these materials display a high degree of selectivity to molecular guest-exchange, as well as retaining structural framework integrity with guest removal. Investigations into the direct application of these phases for enantioseparation are underway, with an aim towards designing systems for the separation of small drug-precursor molecules.
In-situ Structural Investigations: We have recently performed unique in-situ single crystal X-ray diffraction experiments into guest desorption to demonstrate the microporosity of specific molecular framework materials. These studies are noteworthy in providing the first quantitative proof that desolvated phases of both co-ordination and hydrogen-bonded framework lattices may be robust enough to support large regions of complete void, thereby drawing a direct link with more conventional microporous materials such as zeolites. Such studies are being combined with in-situ techniques such as DSC/TGA, vibrational spectroscopy, NMR and molecular modelling to generate an overall picture that combines structural information with an understanding of the selectivity, dynamics and energetics of guest-exchange.
Electronic and Magnetic Properties: The incorporation of atomic or molecular constituents with electronic or magnetic function (e.g., localised electrons, delocalised pI-systems, redox-active species, etc.) into molecular frameworks is being investigated with an aim towards constructing materials with novel electronic and magnetic properties. The vast control over structure and chemical functionality that is afforded by this molecular approach allows the property-directed design and synthesis of new magnetic and electronic materials, including, importantly, the possible combination of these properties with microporosity.