Preparation And Properties Of Cobalt-based MOF Materals

The metal-organic framework material is a kind of coordination polymer which has developed rapidly in the past several decades.It has a three-dimensional porous structure,which have a wide range of applications in the catalytic,storage and separation.In this article,we have synthesized some cobalt-based compounds with different ligands,and then tested the properties of the cobalt-based compounds,mainly to test their application in the color response and the oxygen evolution as electrocatalytic product.The specific works is as follows:1.The preparation of cobalt-based Prussian blue analogue with the properties of thermochromism and solvatochromismThe cobalt-based PBA analogs were synthesized in water by cobalt acetate and potassium hexacyanocobaltate(III)in a very simple solution method,and morphology and size of the PBA synthesized by adding different amounts of sodium citrate was different.The mechanism of the experimental and theoretical calculations were used to shows that the substitution of part of the ligand water molecules by citrate occurred on Co(II),which restrained the leaving of water due to the formed hydrogen bonds between the hydroxyls of citrate and water molecules as well as the steric-hinerance effect of citrate.Therefore,by adding different amounts of sodium citrate in the initial reaction,it is possible to achieve the full potential of the thermochromic material by adjusting the thermally induced transition temperature from 40? to 80?.Other than the tunable color transition temperature,the product also shows the characteristics of high color transition speed and long term stability as a thermochromic material.In addition,such PBAs also have a solvent-induced discoloration phenomenon,when immersed in water,a variety of alcohols,acetonitrile and other solutions,showing different colors,but at the same time when using the PBA-300 as product,the presence of citrate also makes the product Solvatochromism phenomenon failed to appear when immersed in different solutions which can maintain six coordination of divalent cobalt(pink)not changed,This phenomenon also can show the role of citrate in the inside.2.The preparation and properties of 3D nano-flowers hierarchical cobalt-based MOFA cobalt-based MOF was synthesized by a very simple method using cobalt acetate,nickel acetate and terephthalic acid.This MOF exhibited uniform flower shapes formed by intercalating into thin layers.The microstructure of the MOF was determined by XRD,TEM,SEM,FTIR and XPS.And We can study its synthesis mechanism by adjusting the addition of different proportions of cobalt nickel.The electrochemical oxygenation(OER)test was used as an electrocatalyst to compare the catalytic performance of the series MOFs.It was found that the performance of all the ratios was greatly improved compared with that of the former.Especially the MOF Co7Ni3-BDC property was better than others.Its initial potential in 1M KOH solution is only 1.44V,and overpotential is only 334mV when to achieve the current density of 10mA cm-1,which tafel slope is only 72mV/dec more than many oxides,sulfide materials catalytic performance conversed by MOF materals.