Hydrothermal Synthesis And Characterization Of Novel Metal Organophonates/Phosphites Open-frameworks

The family of metal phosphorus-based microporous compounds has a rich composition, including metal phosphates and phosphites, metal organophosphonates and other inorganic-organic hybrid compounds. In recent years, metal phosphorus-based frameworks have been extensively researched due to their rich chemical composition, novel structural topology and potential application in the fields of optics, electricity, magnetism, bio-sensing, medical diagnostics, catalysis, adsorption and separation.Novel metal phosphites, an important family member of the metal phosphorus-based acid framework, have been synthesized by using phosphite as a substitute to phosphate. Recent literature reports metal phosphites synthesized from transition, main group and rare earth metal. As compared to metal phosphates, metal phosphites possess two characteristics which lead to a high level of structural diversity, the coordination mode of metal cations is varied and the structure of phosphate anion is changed. The rich chemical composition, novel topology and structure of metal phosphites, makes the design and synthesis of these materials a promising research area. Oxalate exhibits a rigid coordination geometry, it has been incorporated into the synthesis of metal phosphates, thus allowing the formation of novel inorganic-organic hybrid metal phosphite-oxalate frameworks. The successful synthesis of metal phosphite-oxalate has enriched the structural chemistry of metal phosphorus-based acid frameworks.Novel metal organophosphonates were hydrothermally prepared by using organic phosphonic acid as a substitute for phosphate. Inorganic-organic hybrid frameworks of metal organophosphonates are a new member of the metal phosphorus-based microporous family of compounds. This new class of materials possesses the following two advantages:high thermal stability and ease of structural modification through modification of organic moieties. The development of synthesis of organophosphates has been well studied and greater emphasis is now placed on rational design as well as studying and improving the functionality of these materials.There is limited literature on indium phosphite compounds as compared to the large number of reports of transition metal phosphite. This work is focuses on the synthesis and structure characterization of novel indium phosphite, indium phosphite-oxalate as well as metal organophosphonates involving cadmium and nickel. The primary research results are listed as follows:(1) Reactions of NTP with Cd(oac)2 under hydro thermal conditions afforded two novel 3D cadmium organophosphonate compounds Na|Cd2 [N(CH2PO3H)(CH2PO3)2(H2O)](JCdP-1) and Na2|Cd5[N(CH2PO3)3]2(H2O)2| (JCdP-2). NTP was gradually deprotonated under different acidity conditions and chelated with Cd2+ to produce different secondary building units (SBU), these SBUs combined and constructed the novel structures of JCdP-1 and JCdP-2.JCdP-1 was synthesized under neutral condition with a pH value close to 7. Its framework is constructed from cadmium cations and NTP anionic ligands connected through covalent and hydrogen bonds. Sodium cations are in the free volume to balance the negative charges from the framework. In the coordinated network of JCdP-1, each anionic NTP adopts aμ7 coordinated model, chelating with two cadmium cations to form a new secondary building units SBU-1, formulated as Cd2(NTP) and bridging with other five cadmium cations through CPO3, resulting in the 3D coordinated network structure of JCdP-1.JCdP-2 was synthesized under weak condition with a pH value close to 8. Its framework is constructed from cadmium cations and NTP anionic ligands connected through covalent and hydrogen bonds. In the coordinated network of JCdP-2, each anionic NTP adopts aμ8 coordinated model, chelating with three cadmium cations to form another new secondary building units SBU-2, formulated as Cd3(NTP). SBU-2 is bridged with five other cadmium cations through CPO3, resulting in the 3D coordinated network structure of JCdP-2. There exists a one-dimensional channel along z axis and sodium cations are in the channels to balance the negative charges from the framework.(2) A novel 2D layer structure of|H2O|[Ni3(O3PCH2-NC4H7-CO2)2(H2O)4](JNiP-3) was hydrothermally prepared by using A/-(phosphonomethyl)proline (H3L) as a ligand. The structure of JNiP-3 is constructed from alternating vertex-sharing or edge-sharing NiO6 (or NiO5N) octahedra and O3PC tetrahedral. The cyclopentyl moiety of H3L is grafted onto the layer through coordination of CPO3, CO2 and (CH2)2NCH2 with central nickel atoms and directed into the interlayer spaces. There exists a one-dimensional rhombohedra 12-MRs channel in the [001] direction, water guest molecules are located in the channels. Magnetic studies show that JNiP-3 exhibits a paramagnetic behavior.(3) Oxalate was incorporated into the synthesis system of indium phosphite and two novel indium phosphite-oxalate compounds |C4H12N2|[In2(HPO3)3(C2O4)] (JInP-4) and|C6H14N2|[In2(HPO3)3(C2O4)] (JInP-5) were prepared in the hydrothermal system of In(NO3)3·4H2O-H3PO3-H2C2O4-organic amine. The two hybrid frameworks obtained possess different framework topologies.JInP-4 was hydrothermally synthesized using dabco as an organic templating agent. Its 3D open-framework structure is constructed from vertex-sharing InO6 octahedra, HPO3 pseudo-pyramidal and C2O4 groups. The assembly of these building units generates intersecting channels along two different directions. Contained within the channels are protonated dabco molecules, which interact with the host framework through hydrogen bonding. In the structure of JInP-4, the oxalate groups are incorporated into the indium phosphite layer thus changing the structure of the hybrid layer. The chelating coordination of the oxalate with indium, InO6 has distorted octahedral geometry. Another structural feature of JInP-4 is the presence of left-handed and right-handed helical chains.In the presence of piperazine as an organic template agent, JInP-5 was prepared under hydrothermal conditions. Its 3D open-framework structure is constructed from alternating vertex-sharing InO6 octahedra, HPO3 pseudo-pyramidal and C2O4 groups. Firstly, InO6 octahedra and HPO3 pseudo-pyramidal are linked alternatively to form a 4,8-ring 2D layer. These 2D layers stacked in an AB sequence with oxalate groups acting as a bridging ligand thus forming the novel 3D hybrid framework. There existed 8,8, and 12-ring multi-dimensional intersecting channels, which contain protonated piperazine molecule. The phase transformation of JInP-5 was also investigated.(4) In the presence of different organic amine as template, two novel 3D open-framework structure of indium phosphite|(C4H12N2)0.5(H3O) [In4(H2O)3(HPO3)7](JInP-6),|(C10H10N2)1.5(H30)3|[In18(H2(HPO3)16 (H2PO3)6](JInP-7) and a novel layered structure of indium phosphate |H3O|[In(HPO3)2](JInP-8) were successfully synthesized under hydro thermal conditions. The investigations revealed that:an increase in the size of the organic template resulted in compounds featuring large channels.JInP-6 was hydrothermally synthesized by using piperizine as a template. Its structure can be described as follows:Firstly, InO6 (or InO5H2O)) octahedra, HPO3 pseudo-pyramidal linked alternatively to form a layer structure with 4,6, and 12-ring windows. These layers are stacked in an AB sequence along the z axis and further connected by InO6 octahedra forming the 3D structure of JInP-6. There are 12-ring intersecting channels along [100] and [010] direction, which contain protonated piperazine and water molecules.Using 4,4'-bipy as an organic templating agent, JInP-7 was prepared under hydrothermal conditions. JInP-7 has the same layer structure as in the structure of JInP-6, two InO6 octahedra and three HPO3 pseudo-pyramidal shared their vertex to from a pentamer, which acts as a pillar connecting these layers into the novel 3D structure of JInP-7. Present are intersecting 16-ring channels along [110] and [010] direction, in which protonated 4,4'-bipy and water molecules were located.In the presence of fluoride ions, JInP-8 was synthesized under hydrothermal conditions. Its 2D layer structure can be described as follows:InO6 octahedra and HPO3 pseudo-pyramidal linked alternatively into a novel secondary building unit (SBU),6*1, these SBUs are further connected through edge-sharing into the layer structure of JInP-8, protonated water molecules are located in the interlayer spaces. From a topological perspective, JInP-8 exhibits a (3,6)-connected layer structure with kgd (kagome dual) topology with a vertex symbol (43)2(46).