Solvent-free Synthesis,structure,and Properties Of Open-framework Metal Phosphate-oxalates

Crystalline inorganic-organic hybrid solids have attracted considerable interests because of their potential applications in ion exchange,gas adsorption,separation and catalysis.These compounds are usually synthesized under hydrothermal,solvothermal and ionothermal conditions.Hydrothermal and solvothermal methods have several deficiencies,such as strong solvation effect,high system pressure,and pollution caused by using organic solvent.Ionothermal method has the disadvantage of high cost by using the expensive ionic liquid as solvent.Solvent-free synthesis method does not add additional solvent,which not only eliminates the disadvantages of above-mentioned solution-mediated syntheses,but also can be used for the preparation of those compounds that are unstable in the solvent.It is a safe and effective synthetic method.In this thesis,a series of new metal phosphate-oxalate hybrid solids have been synthesized under solvent-free condition.The crystal structures of these compounds were determined by single crystal X-ray diffraction.These compounds were further characterized by powder X-ray diffraction,IR spectroscopy and thermogravimetric analysis.The magnetic and fluorescence properties of part of compounds were also investigated.The thesis is divided into seven chapters.In the first chapter,the classification,research development and synthesis methods were introduced briefly.The research purpose and research significance of this thesis were also introduced in this chapter.In the second chapter,we investigated the templating effect of different organic amines on the structures of manganese phosphate-oxalates.Two compounds have been synthesized under solvent-free condition using piperazine as template.They have the same pcu topology but different magnetic properties.Using different organic templates,we prepared chainlike,single-layered,double-layered,and three-dimensional open-framework structures.The functions of inorganic and organic substructures of these structures were studied.The magnetic properties of these compounds were also investigated.In the third chapter,the influence of different metal ions(Mn²⁺,Co²⁺,Zn²⁺,Cd²⁺,Al³⁺,Ga³⁺,In³⁺)on the metal phosphate-oxalates hybrid frameworks was investigated by using the same amine as template.New hybrid compounds with zero-,two-,and three-dimension structures were synthesized,which display diverse topologies such as hcb,mmt,ins,fsd.To expand the range of metal ions of metal phosphate-oxalates,the first example of a cadmium phosphate-oxalate was synthesized in this work.A new compound with extra-large 20 MR channels was successfully obtained under solvent-free condition,which was the first metal phosphate-oxalate with 20 MR channels.Prior to this work,the largest pore opening in metal phosphate-oxalates is 16 MR.In the fourth chapter,five metal phosphate-oxalate hybrid compounds with extra-large16 MR channels have been synthesized under solvent-free condition.Compound 20 and 21have the same zeolitic CrB₄ topology,and such topological structure is first observed in metal phosphate-oxalates.Compound 21 emits clear blue luminescence under excitation of365 nm UV light.In the fifth chapter,the synthesis of bismuth phosphate-oxalate hybrid compounds was explored under solvent-free condition,demonstrating the advantage of desolvation function of solvent-free method in the synthesis of new compound.The hydrolysis process associated with bismuth ions is difficult to control and often leads to the formation of intractable solids that are difficult to be crystallized.For this reason,solvent-free method was used to replace other methods such as hydrothermal and solvothermal methods.Four bismuth phosphate-oxalates with two-dimensional double-layers and three-dimensional open-framework structures were synthesised under solvent-free condition.Compound 22has extra-large 16 MR channels.In the sixth chapter,two novel structure-directing effects of amines on specific networks were discussed.The first one is to finely tune metal-organic skeletons to form different nanobelt-like,layered,and three-dimensional structures by keeping the whole framework and metal-inorganic skeleton unchanged.And the second one is that the amine molecules can reverse the structure-building roles of metal phosphate skeleton and metal oxalate substructure for formation of the same framework topology.In the seventh chapter,the main achievements of this thesis were summarized.The future research in the field of crystalline inorganic-organic hybrid solids has also been proposed.