Study On The Synthesis Process Of New Prussian Blue Analogues By Isothermal Titration Calorimeter

In recent years,isothermal titration calorimeter has been widely used to study various interactions because thermodynamic properties of some processes could be detected and the detected heat is non-specific.Exploring the thermodynamic properties of interactions allow us to analyze problems from the perspective of thermodynamics and give us theoretical guidance to solve problems.In this paper,the thermodynamic properties of trimetallic Prussian blue analogues and the modified Prussian blue analogues were investigated by isothermal titration calorimetry,respectively.The reasons of enhancement on the catalytic effects of trimetallic Prussian blue analogues and the modified Prussian blue analogues on epoxidation of styrene were analyzed thermodynamically.The details are as follows:Firstly,we studied the thermodynamic properties of synthesis processes of trimetallic Prussian blue analogues.A series of trimetallic PBAs were obtained by adding Fe or Cu elements to several bimetallic PBAs:FeCdCo PBA,FeCoCo PBA,FeMnCo PBA,FeZnCo PBA,CuFeCo PBA,CuCdCo PBA,CuCoCo PBA,CuMnCo PBA and CuZnCo PBA,and the obtained trimetallic PBAs were applied to the epoxidation of styrene,respectively.The experimental results show that the catalytic effects of trimetallic PBAs are generally better than the corresponding bimetallic PBAs.Then,trimetallic Prussian blue analogues were characterized by infrared,X-ray diffraction?XRD?and scanning electron microscopy?SEM?,respectively.CuZnCo PBA,CuFeCo PBA and corresponding bimetallic PBAs were also characterized by N₂adsorption and desorption and X-ray energy spectrometer?EDS?.Finally,the thermodynamic properties of CuZnCo PBA,CuFeCo PBA and their corresponding bimetallic PBAs were explored by isothermal titration calorimetry.It is shown that their synthesis processes are all spontaneous exothermic processes.The enthalpy changes of the two trimetallic PBAs are between that of the respective corresponding bimetallic PBA,and their catalytic effects are in reverse order with their respective enthalpy change.The PBAs with smaller enthalpy change have better catalytic effect.The size of the Prussian blue analogue particles and the type of metal elements also have a certain influence on the epoxidation of styrene.Secondly,based on the previous research of our laboratory,the thermodynamic properties of the synthesis process of various alcohol-FeCo PBA were further studied.It is shown that the synthesis processes of FeCo PBAs modified by different carbon chain length alcohols are all spontaneous exothermic processes and are driven by enthalpy.In addition,the order of the enthalpy of their synthesis is consistent with the order of their catalytic effects in the epoxidation of styrene,that is,the larger the enthalpy value is?the less heat release?,the better the catalytic effect is.The synthesis processes of FeCo PBAs modified with different hydroxyl number alcohols are also spontaneous exothermic processes.For the same type of alcohols with different number of hydroxyl groups,the better the catalytic effect is,the larger the enthalpy is?that is,the less heat release?.In addition,the synthesis processes of 1,3-propylene glycol-FeCo PBA and 1,5-pentaerythritol-FeCo PBA with better catalytic effect are both driven by entropy and enthalpy and the main forces are hydrophobic interaction and hydrogen bond.However,the synthesis processes of FeCo PBA modified by other alcohol hydroxyl are enthalpy-driven processes.The main interaction forces are van der Waals force and hydrogen bond.Therefore,the catalytic effect of FeCo PBA modified with different hydroxyl number alcohol in the epoxidation of styrene may be related to the interaction force of the synthesis process.Finally,we studied the thermodynamic properties of synthesis process of a series of the amide-FeCo PBA by isothermal titration calorimetry.It can be seen from the catalytic results that all the amide-FeCo PBAs can improve the catalytic effect of the epoxidation of styrene.It is displayed by thermodynamic data that the synthesis processes of amide-FeCo PBA are spontaneous and exothermic.Furthermore,for the amide-FeCo PBA,the larger the enthalpy is,the better the catalytic effect is.Additionaly,for N-methylformamide-FeCo PBA,N,N-dimethylformamide-FeCo PBA and N,N-dimethylacetamide-FeCo PBA,which catalytic effects are much better,the processes are driven by entropy and enthalpy and the interaction forces are hydrophobic interaction and hydrogen bond.For other amide-FeCo PBAs,they are enthalpy-driven processes and their interaction forces are van der Waals force and hydrogen bond.From the thermodynamic point of view,the reason why the amide-FeCo PBAs have better catalytic effect in the epoxidation of styrene is that the strong interaction between the amide and the cobalt in the product PBA,which in turn affects its active metal Fe.On the other hand,the different interaction forces of synthesis processes of the amide-FeCo PBA also have a certain effect on its catalytic effect.