Preparation And Catalytic Performance Of Porphyrin MOFs Supported Metal Nanoparticle Composites

Metal porphyrin organic frameworks（P-MOFs）are porous materials with high surface area using metalloporphyrins as organic ligands and exhibit various applications in energy storage,luminescent materials,sensors,etc.,especially in the field of catalysis.MOFs have advantages in catalysis due to their high density and uniformly dispersed active sites;high pore structure,which makes all active sites easily accessible;and open channels,which greatly facilitate the transport and diffusion of substrates and products.However,the type of active sites on the MOF structure is mainly limited to the following two sources,resulting in limited reactivity for a limited number of catalytic reactions.（1）Unsaturated metal central nodes,which behave as Lewis acid sites,are usually obtained by removing the coordinating solvent after activation.（2）Active sites grafted on organic linkers.As a class of porous materials,in addition to introducing active sites into the MOF structure,MOFs can also incorporate catalytically active guest species into their pore space or stabilize on the MOF surface,thereby enhancing their catalytic activity.For example,by encapsulating metal nanoparticles（MNPs）within MOF materials,the synergistic effect between the two components can enhance the catalytic performance or expand the reaction range.In this paper,by using different methods to grow different metal nanoparticles on metalloporphyrin organic frameworks,a class of composite catalysts material with good oxidative coupling reaction and excellent photocatalytic degradation of organic dyes in polluted water were obtained.This thesis has two main experimental components as follows:（1）We first synthesized tetracarboxyphenyl copper porphyrin and verified it by FT-IR spectroscopy,and then used a one-pot method to synthesize mesoporous MOFs PCN-222（Cu）with metalloporphyrin as the organic building block,which is based on an octal Zr₆ cluster MOFs formed by nodes and tetrakis（4-carboxyphenyl）copper porphyrin（Cu-TCPP）ligand units.Then,copper chloride solutions of different concentrations were immersed into the pores of the MOF by the double-solvent method,and after reduction,copper nanoparticles of a certain shape and crystal form were encapsulated in the pores of PCN-222（Cu）to obtain copper nanoparticles with different loadings of nano-copper.Composite catalyst Cu@PCN-222（Cu）.The obtained catalytic materials were characterized by X-ray diffraction,electron microscopy,X-ray photoelectron spectroscopy,etc.The experimental results of terminal alkyne coupling catalysis show that,With CHCl₃/dioxane as the reaction solvent and TMEDA as the ligand,good yields of 1,4-diphenylbutadiene（45.3-81.7%）were obtained when Cu@PCN-222（Cu）with different copper nanoparticles was used as the catalyst.Among them,Cu@PCN-222（Cu）-2 has the strongest catalytic activity and the highest product yield.both linear and aryl terminal alkynes can be converted to the corresponding products very efficiently.（2）Metal-free tetracarboxyphenyl porphyrins were synthesized as ligands for MOFs.Then,the parent MOF-525 was synthesized by a two-step method using zirconium oxychloride as the zirconium source.It is a uniform cubic MOF formed by six-linked Zr₆cluster nodes and tetracarboxyphenylporphyrin ligands.The composite material Ag@MOF-525 with silver nanoparticles supported on the surface was obtained by photoreduction method by adding it into silver nitrate solution for uniform dispersion.It was found by electron microscopy that the cubic structure of MOFs was still preserved,and a large number of silver nanoparticles were loaded on the surface of the cubes.The XRD of MOF-525 and Ag@MOF-525 were tested respectively,and it was found that the characteristic peaks of XRD were almost unchanged,and no peaks of silver nanoparticles were detected,which was caused by the less content and uniform dispersion of nanoparticles.Then Ag@MOF-525 was used as a catalyst to degrade the organic dye Rh B under visible light,and it was found to have excellent photocatalytic activity.It can completely degrade organic dyes within 1 hour,and the degradation rate still reaches more than 80%after repeated use for five times...