Preparation And Properties Of Metal Borate

Borates have potentially optical applications due to their unique physical and chemical properties.An increasing attention has been focused on the synthesis of borates with novel framework structures.In the past decades,the borates were primarily synthesized through high-temperature solid-state reactions or boric acid melting approaches.Recently,relatively mild hydrothermal or solvothermal methods have been used for the introduction of main group metals,transition metals and rare earth metals into borate systems,endowing these materials special physical and chemical properties and even framework chirality.This contributes to effective strategies for the synthesis of borates with excellent non-linear properties.Our group has focused on the synthesis of novel borates and metal borates using metal complex（MC）templates for a long time.As a continuation of our previous work,here this thesis presents the synthesis of a novel series of metal borate compounds,which were throughly characterized by single-crystal and powder X-ray diffraction（XRD）,FTIR,UV-vis,thermogravimetric and elemental analysis.These compounds can be divided into two categories:1.Main group metal borates.The hydrothermal reaction of Al（i-Pro）₃ and H₃BO₃ leads to the formation of three MC-templated aluminobortes,i.e.Cd（en）（1,4-dab）_0.5[AlB₅O₁₀]（2-1）（en=ethylenediamine,1,4-dab=1,4-butanediamine）Cd（en）（1,3-dap）[AlB₅O₁₀]（2-2）（1,3-dap=1,3-propanediamine）[Cd（en）（dien）H₂O][AlB₅O₁₀]（2-3）（dien=diethylenetriamine）All the compounds 2-1,2-2 and 2-3 feature three-dimensional structures constructed by AlO₄ tetrahedra and B₅O₁₀ clusters.The templates are metal complex cations,where the metal centers are exclusively coordinated by two types of organic amines.The different conformations of the MCs contributes to the formation of different framework structures.In the framework of 2-1,there are two kinds of8-member ring channels and one type of 11-member ring channel running along the c-axis and a-axis,respectively.And the space of the channels are filled by dimeric metal complex cation[Cd₂（en）₂（1,4-dap）]⁴⁺.The framework of 2-2 consists of11-member ring channels running along the a-,b-and c axis,templated by one-dimensional cationic polymer.The MCs in 2-1 and 2-2 are connected to the framework through coordination bonds.In 2-3,the 11-member ring channels are running along the a-axis,whereas the 8-member ring channels are running along the b-and c-axis.The metal Cd in the MC forms a distorted octahedral configuration and is interacted with the framework by hydrogen bonds.2.Transition metal borates.Three polyoxovanadium borates and two vanadates were prepared under solvothermal conditions.（HMA）₁₃Zn（H₂O）₂{V（MA）₂（Zn₂O₃）₂[B（OH）₂][（VO）₁₀(B₁₄O₃₀)₂]}（3-1）（MA=methylamine）[（H₂DAP）（HMA）H₃O]₂{[B₂O（OH）₂]（VO）₆[B₁₀O₁₉（OH）₃]₂}（3-2）（HMA）₈{B（OH）（VO）₆[B₁₀O₁₉（OH）₃]₂}·4H₂O（3-3）（HMA）₂MnV₂O₇（3-4）（HMA）₂CdV₂O₇（3-5）Compounds 3-1,3-2 and 3-3 are all constructed by the boron-vanadium clusters with sandwich structures.The 3-1 structure contains{V₁₀B₂₈}clusters,which are connected via BO₃ groups to form a novel,unpreccedent three-dimensional structure.In addition,there are two{Zn₂O₃}units suspended in the center of the{V₁₀B₂₈}cluster through three oxygen atom bridges.Each Zn₂ unit is connected with a half-occupied V（MA）₂ extending to the outside of the boron-vanadium cluster and a half-occupied B（OH）₂ inside of the boron-vanadium cluster.Boron vanadium clusters are connected by the half-occupied Zn（H₂O）₂ unit to form a three-dimensional structure with a bcu topology.Both the 3-2 and 3-3 structures contain{V₆B₂₀}clusters,but the connection methods are different.The{V₆B₂₀}cluster in 3-2 is connected by a B₂O₅ dimer to form a one-dimensional structure.In 3-3,the BO₄ in the center of the B₁₀ unit on the{V₆B₂₀}cluster and the BO₃ triangle in one corner of the B₁₀ unit on another V₆B₂₀ cluster are connected to form a one-dimensional chain structure.3-4 and 3-5 are isomorphic vanadate.The compounds use organic amines as counter ions,and the V₂O₇ cluster is connected to MO₆（M=Mn,Cd）to form a novel three-dimensional structure.