Ultrafast Synthesis,Activation,and Catalytic Performance Of Hf-based 2D Metal-Organic Layers

The metal-organic layer（MOL）is composed of metal ions/metal oxygen clusters and organic ligands assembled through coordination bonds to form a 2D thin layer material.It has the characteristics of large specific surface area,many active sites,and good mechanical flexibility.It is widely used in gas separation,Sensing,energy storage and transfer,and catalysis.In this thesis,a microwave-assisted solvothermal method was used to rapidly synthesize a hafnium-based 2D MOL,and MOL was successfully activated by heat treatment and chemical treatment.The chemical warfare agent simulant dimethyl paraoxon（DMNP）was used as the research model,The catalytic performance of MOL is explored toward the degradation of DMNP.The main research contents are as follows:（1）Selecting Hf Cl₄ as the metal source,1,3,5,-tris（4-carboxyphenyl）benzene（BTB）as the ligand,using microwave-assisted solvothermal method,the influence of the heating time,holding time,the type and content of the modulator,the solvent,the expansion reaction on the MOL have been systematically investigated.It is found that using formic acid as a regulator,the MOL is successfully synthesized ultra-fast in 2minutes.This is currently the fastest method for 2D MOL synthesis,and the highest space-time yield is 2875 kg m^-3 day^-1.This method can obtain a single pure-phase MOL under a variety of conditions,and has good reaction adaptability,rapid reaction,high space-time yield,can amplify the reaction.These characteristics enhanced possibilities to scale-up and industrial production for the further development and application of 2D MOL.（2）Two ways of heat treatment and chemical treatment to activate the MOL is explored to change the chemical environment of the metal nodes of the metal-organic layer.The effects of heating temperature,heating time and hydrochloric acid treatment activation on the MOL have been studied respectively.Heat treatment activation can completely remove the solvent molecules in the metal organic layer and effectively remove the small molecules coordinated with the metal center and the hydrogen on the bridged hydroxyl group（μ₃-OH）in the metal nodes.Chemical treatment activation can completely remove the solvent molecules in the metal organic layer,and can effectively replace part of the blocked carboxyl groups coordinated with the metal nodes with water molecules,but the degree of substitution depends on the specific sample.Both methods successfully changed the chemical environment of the metal nodes and achieved a great activation effect.（3）The effects of modulus in the synthesis process,amplification synthesis,and different activation methods（heat treatment activation,chemical treatment activation）on the catalytic performance of the MOL is explored,and the mechanism of the catalysis of the MOL in the decomposition of DMNP by means of theoretical calculation is revealed.The MOL synthesized with formic acid or hydrochloric acid as modulator has excellent catalytic performance,and the half-life of the catalytic reaction of DMNP is less than 3 min.For the reaction with formic acid as the modulus,after the amplification reaction,the product still maintains excellent catalytic performance.Both heat treatment activation and chemical treatment activation will reduce the catalytic activity of the MOL to varying degrees.Theoretical calculations show that the coordinated hydroxyl groups on the surface of the metal nodes play an important role in the catalytic performance,while the catalytic performance of MOL with the terminal formate is significantly lower than that with the terminal hydroxyl group.