Design Synthesis And Properties Of Copper-rich Framework Chalcogenidometalates

Microporous chalcogenides are important inorganic multifunctional materials, not only because they have diverse structures, but also can integrate porosity with semiconductivity that are lacking in most other microporous materials (such as zeolites, and metal-organic frameworks), and are promising for applications in many fields, such as selective ion-exchange, photoelectrocatalysis, solar energy transfer and fast-ion conductivity. Therefore, the synthesis and property study of novel microporous chalcogenides are becoming an active area of solid state chemistry. Recently, large numbers of open-framework chalcogenides have been synthesized using solution-assembly approach and solvothermal(hydrothermal) technique. Among the microprous chalcogenides family, the majority are ternary chalcogenides and based on main group chalcogenido-anionic building units, while microporous quarternary chalcogenides are rare, especially with high transition-metal containing due to preference to form insoluble transitional metal chalcogenides. The key of successful construction of polynary framework chalcogenides is to search for suitable mineralizer to increase the solubility of transition metal chalcogenides under mild solvothermal condition.In this dissertation, we advanced a new synthetic route by using polysulfide Sx2- anions as mineralizer to prevent the formation of Cu2S deposition. Then, we proposed to construct open-framework chalcogenides with Cu-S building units. Using different organic amines or alkali metal cations as structural directing agents, series of copper-rich framework chalcogenides were obtained. Their syntheses, structures, thermal stabilities, ion-exchange, semiconductor properties were studied and discussed in detail.1. Polysulfide Sx2- anions generated under solvothermal condition were used to increase the solubility of copper sulfide and suppress the self condensation between SnS4 units, and then a new strategy was proposed to incorporate high valent main group cations into Cu-S system to explore copper-rich framework chalcogenides built up from Cu-S units. Three copper-rich framework sulfides were obtained with high Cu/Sn molar ratio(Cu/Sn= 2.7). Compound (H2en)2Cu8Sn3S12 (1) was synthesized in pure ethylenediamine sytem under solvothermal condition, and the mineralizer effect of polysulfide Sx2- ions was discussed in detail.1 contains a trigonal CuS3-based 3D framework into which Sn4+ ions are incorporated, and exhibits multiple channel systems and interesting ion-exchange properties. Compound A6Cu8Sn3S13(M=Na+, K+) (2,3) contains 3D copper-rich Cu-Sn-S framework with ReO3 topology, built up from discrete Sn4+ ions linking icosahedral Cu-S clusters, and exhibits 3D channels in which alkali metal cations are located. It is worth noting that these three compounds are based on Cu-S building units, while discrete Sn4+ cations are incorporated into the 3D Cu-S framework or serve as linker to bridge Cu-S clusters to form the copper-rich framework. In particular, there are stable building blocks:icosahedral Cu-S clusters occurring in these structures. The icosahedral Cu-S cluters with high symmetry, behaving like octahedral atoms, can decorate at 6-connected sites (hexagonal or octahedral). Therefore, the icosahedral Cu-S cluster can be used as octahedral building units to design and construct novel framework chalcogenides.2. A new design idea was proposed using icosahedral Cu-S cluter as octahedral secondary building units to construct novel framework sulfides, a series of copper-rich Cu-Ge-S framework sulfides were successfully obtained. Compounds A4Cu8Ge3S12(A= Na+, K+, Rb+) (4,5,6) are isostructural and contain copper-rich Cu-Ge-S framework(Cu/Ge= 2.7) built up from discrete Ge4+ linking icosahedral Cu8S12 clusters, with alkali metal ions residing intersecting channels. The increasing size of the alkali metal ions from Na+ to Rb+ shows negligible influence to the formation of the Cu-Ge-S framework. The structures of 5 and 6 can be derived from cubic perovskite, with K+ or Rb+ located in the cavities, wihle in 4 Na+ cations are partially disordered in the channels. Compound (H2dap)2Cu8Ge4S14·2H2O (7) was synthesized when diprotonated 1,4-dab was used as SDA.7 contains a 3D Cu-Ge-S framework with relative low copper content(Cu/Ge= 2.0) composed of the icosahedral Cu8S12 cluster interconnected with discrete Ge4+ and dimmer [Ge2S2]4+ units. This compound can be considered as an expanded structure of compound 4,5 or 6, and has an expanded structure due to the expansion of the bridging Ge-S units in two directions. Therefore, we not only successfully decorate the octahedral coordinated site with icosahedral Cu-S cluster, but also realized the expansion of simple (6,2) net.3. Our interests have been extended to explore copper-rich framework selenides. A copper-rich framework selenide, Hn(en)3Cu8Sn3Se13 (8), based on mix-valent Cu8Se13 cluster, was obtained in pure en system. Hexagonal closed packing of the icodahedral Cu8Se13 cluster and linked by discrete Sn4+ ions give raise to 3D copper-rich Cu-Sn-Se framework with Hn(en)3n+ located in each cavity. This compound can be derived from hexagonal perovskite structure. Then, thiophenol was introduced into synthesis system to activate Se, and to increase the solubility of copper-selenide, two copper-rich framework selenides Na6Cu8Sn3Se13 (9) and Na6Cu8Ge3Se]3 (10) were successfully obtained. Distinct to compound 8 with hexagonal perovskite structure, these two compounds are similar to cubic perovskite, and constructed from Cu+-based icosahedral Cu8Se13 cluster onions. Primitive cubic packing of icosahedral Cu8Se13 clusters and linked by discrete Ge4+ or Sn4+ produce 3D Cu-Ge/Sn-Se framework with disordered Na+ cations located in each cavity.4. Icosahedral Cu-Se cluster was used as octahedral SBUs, and high valent As5+ was incorporated as links to construct framework copper-rich selenoarsenates. Four coper-rich framework selenoarsenates, (H3dien)Cu8As3Se13 (11)、(H2en)1.5Cu8As3Se13 (12)、(H2dap)1.5Cu8As3Se13 (13)�'�Na2(H2dap)o.5Cu8As3Se13 (14) were successfully obtained. They contain same copper-rich Cu-As-Se framework (Cu/As= 2.7), built up from As5+ ions linking icosahedral Cu8Se13 clusters, with couterions are disordered in 3D channels. Despite the SDAs have different charge, shape and symmetry, the Cu-As-Se frameworks with same charge density and symmetry, suggesting the rigid and high covalent nature of the framework.