A journey from ordered mesostructured chalcogenides to chalcogels: Porous semiconducting metal-chalcogenide aerogels

The work of this dissertation is focused on (1) investigating solution equilibria of soluble metal-chalcogenide building blocks and their role in making well-ordered mesostructures, (2) creating porous metal-chalcogenide frameworks out of well-defined molecular building units, (3) generalizing the synthetic route, (3) investigating their emerging unique properties, and (4) exploring their possible applications.;Surfactant directed assembly of metal chalcogenide building units was shown as a method to construct semiconducting mesostructured materials. The solvent dependence solution equilibria of [Ge2Se6] 4- and [GeSe4]4- were studied in details and it has been observed that the presence of multiple building units favors the construction of highly hexagonal mesostructures with Pt2+. Both surfactant head group and chain length were varied systematically to study their effect on the long range order and optoelectronic properties of the final mesostructures.;A simple metathesis reaction was applied for the first time to generate a broad class of metal-chalcogenide gels and aerogels. It was shown how various chalcogenido clusters, when bound to Pt2+ in water, yield gels having porous frameworks. These gels, referred to as 'chalcogels', were transformed to aerogels after supercritical drying with carbon dioxide. The aerogels possess very high internal surface area, up to 327 m2 /g, with tunable energy gaps between 0.2 and 2.0 eV, and preferentially absorb heavy metal ions.;The successful synthesis of highly active phases made of Co(Ni)/Mo(W)/S for hydrodesulfurization process, was achieved through the extension of this sol-gel chemistry. The soft chalcogenide surfaces of these low density aerogel networks can absorb conjugated organic molecules, mercury ions, and can preferentially absorb CO2 over H2.;The use of a metathesis reaction to generate metal chalcogenide aerogels was extended to other main group (e.g. Sb3+, Sn2+) and transition metal ions (e.g. Mn2+, Fe2+, Co2+, Ni2+, Zn2+) and different building units such as [SnS4]4-, [SnSe4] 4-, [Sn2Se6]4-, [SbSe4] 3-, [Sn2S6]4- and [P2S 6]4-. Use of ligated metal ions and formamide as a solvent helps to slow down the reaction and forms an extended polymeric network. Aerogel frameworks made of heavier elements with high surface polarizability showed higher gas separation performance.