Plasma/Microwave Induced Defects In Metal-organic Frameworks And Its Catalytic Applications

Metal organic framework?MOF?has the characteristics of high porosity,large surface area and designable,so it is widely applied in aspects of gas adsorption/desorption,electrochemical,heterogeneous catalysis and so on.Especially,in the field of heterogeneous catalysis,the research on MOF has received a lot of attention.Each component of the framework can be used as a catalytic active site,such as open metal sites,modified organic ligands or non-framework groups in the pores.However,there is a little previous researchs about the influence of MOF defects on catalytic performance.From the perspective of MOF defe cts,plasma etching,microwave synthesis and microwave acid treatment are used to induce and control MOF defects while maintaining the stability of MOF structure.Styrene epoxidation,esterification,transesterification and citronellal cyclization were use d as reaction models to systematically study the effects of defects on the catalytic performance of MOF.The main contents are as follows:?1?Plasma etching was used to induce the defects of HKUST-1,and then the products were used for epoxidation of styrene reaction.The treated HKUST-1samples with roughner surface and lower crystallinity,and ligands defects occurs,resulting in the formation of unsaturated metal open sites.Besides,the prepared samples were characterized by TGA,BET,EXAFS,XANES to prove the apprance of defects.When the P-HKUST-1 as catalyst,the styrene conversion was as high as 98%and the material shows good stability.?2?UiO-66 and MOF-808 with high stability are treated with acid as MOF with Zr₆O₄ cluster as basic secondary building unit.The use of microwaves provides tremendous energy for post-processing,accelerating the acid etching effect of on the material.The results showed that the content of ligands in the framework was significantly reduced and the specific surface area was increased in the microwave-treated MOF materials.In the catalytic tests,the catalytic performance of the acid-treated MOFs was significantly improved,and the crystal structure remained stable.?3?A series of UiO-66 and MOF-5 samples with different time were prepared by rapid microwave synthesis.The XRD,BET and TGA characterizations consist of catalytic tests,showed that the microwave method can greatly shorten the materials synthesis time and accelerate crystal growth,moreover,the defects for mation is reated to synthesis time.Compared to traditional heating synthesis,microwaves synthesis help MOFs provide better catalytic properties...