Synthesis,Structure And Properties Of Novel Metal Diphosphonates Coordination Polymers

Metal phosphonates are compounds which have great potential in the field of inorganic-organic hybrid materials.These material have outstanding characteristics including good thermal stability,acid and alkali resistance,mild synthesis conditions,and stable skeleton organic function group.They have extremely performance and potentials in the field such as gas adsorption,photocatalysis,solar cells,ion selective materials,and anticorrosion.The target compounds could be directly synthesized by designing the ligands and modifying the phosphonic acid ligands with different types of function group.Moreover,the structure of many metal phosphonate coordination polymers are predictable,and the target metal phosponate contain the designed features.Compared with the monophosphonic acid ligands,the bisphosphonate ligands have more coordination points,and show diverse coordination methods.So bisphosphonate ligands enable the structure and feature of the material to be more changeable,and become a top research topic.In this article,2,5-dimethylbenzene-1,4-diylbis?methylene?diphosphonic acid is synthesized from the paraxylene.Because this ligand has many phosphonyls and hydroxyls,which could be the coordination points of the hydrogen bonds.In this way,the frame structure is easier to be achieved.According to the above introduction and previous research achievements,a reported bisphosphonate complex and seven unreported new bisphosphonate complexes are synthesized by utilizing H4L as the ligand and the hydrothermal synthesis.The materials were characterized by X-ray single crystal diffraction,X-ray powder diffraction,infrared spectroscopy,and thermogravimetric analysis.The chemical formula of the synthesized complex is as follows:Mg?HO₃P-CH₂C₆H₄?CH₃?₂CH₂PO₃H?₃ 1,Ca?HO₃PCH₂C₆H₄?CH₃?₂CH₂PO₃H?·2H₂O 2,Fe₂?HO₃P-CH₂C₆H₄?CH₃?₂CH₂PO₃H?₃·9H₂O 3,Ni?HO₃PCH₂C₆H₄?CH₃?₂CH₂PO₃H?·4H₂O 4,Cu₂?O₃PCH₂C₆H₄?CH₃?₂CH₂PO₃?·2H₂O 5,Zn?HO₃PCH₂C₆H₄?CH₃?₂CH₂PO₃H?6,Cd?HO₃PCH₂C₆H₄?CH₃?₂CH₂PO₃H?7,Tb₂?HO₃PCH₂C₆H₄?CH₃?₂CH₂PO₃H?₃·2H₂O 8.Complex 4 is a one-dimensional chain structure formed by the connection between the ligands.And a three-dimensional supramolecular structure can be generated under the influence of hydro bends.Complex 1 and 2 are two-dimensional layered structure.Complex 3,5,6,7,and 8 are three-dimensional net structure.The thermal stability study shows that the eight complexes all have good thermal stability and the decomposition temperature can reach more than 200 ^oC,but the thermal stability has slight differences due to the different structures.The research about degradation of methylene blue solution of complex 3 and 5shows that complex 3 has good degradation ability under ultraviolet conditions.With the increase of complex 3,the degradation effect increases.When the concentration of methylene blue increases,the degradation rate decreases.When hydrogen peroxide is added to the degradation system,the degradation effect is greatly improved.Meanwhile,study shows that the degradation effect of complex 3 is directly affected by the light source.The stronger the ultraviolet light source could increase the degradation rate.There is almost no degradation under visible light conditions.The degradation result of complex 6 is almost the same with complex 3,but the influence from light source on the degradation is different.There is aso almost no catalytic degradation under visible light condition for complex 5.The ultraviolet condition has the catalytic effect,but the intensity of ultraviolet light could not affect the degradation rate.