Preparation And Catalytic Performance Of Metal Organic Framework Materials Based On Porphyrin And Imidazole Ligands

Metal organic framework materials(MOFs)are ordered porous crystalline materials synthesized from metal salts and organic ligands through modulators.Its structure is easily modifiable,so it has a wide range of uses in chemical catalysis.Although there are many types of MOFs,the performance of various types of MOFs has certain deficiencies.The two types of MOFs synthesized in this article are both improved structures of existing types of MOFs to further improve their catalytic performance.Moreover,both of these materials are improved by adopting the bimetal structure,which is easy to play the synergistic effect of the bimetal.MOFs based on metalloporphyrins are rich in N in the structure,and their catalytic activity can be further adjusted by pyrolysis,because they easily form a metal-nitrogen-carbon structure with high catalytic activity after pyrolysis.The same imidazole-based ZIF type MOFs also contain rich N elements in their structure and have good catalytic activity.By combining two differe nt node metals,their catalytic activity can be easily adjusted.Through the pyrolysis of bimetal porphyrin MOFs,a kind of carbon dioxide and epoxy compound addition catalyst with good reactivity was obtained;by changing the synthesis method,a kind of bimetal with good oxidative coupling reaction activity was obtained Type ZIF.The reaction of carbon dioxide can effectively improve the greenhouse effect,and the reaction of sodium benzene sulfonate can be used for the development of biomedicine.The main research content of this paper includes the following two parts:(1)We synthesized the organic ligand carboxyl porphyrin and confirmed its structure using hydrogen NMR spectroscopy.Then a two-step method was used to synthesize the parent PCN-224,which is a MOFs with porphyrin as the ligand and metal zirconium as the node.It can be judged that PCN-224 has good physical properties through electron microscopy and N2 adsorption and desorption tests.Then,Zn metal with lower melting point and Co metal with better activity are introduced into PCN-224 to obtain PCN-224-Zn Co₁ with bimetallic ions.Finally,PCN-224-Zn Co₁ was pyrolyzed in a tube furnace at 950 degrees.The experimental results show that pyrolysis volatilizes Zn,thereby releasing more basic sites;at the same time,a suitable ratio of acidic and basic sites is formed in the metal-nitrogen-carbon structure of PCN-224-Zn Co₁-950.The experimental results found that PCN-224-Zn Co₁-950 has a very good catalytic effect on the epoxidation of carbon dioxide.In addition,the catalytic effects of PCN-224,PCN-224-Zn Co1 and PCN-224-Zn Co1-950 are compared.The experimental results show that the catalytic effects of PCN-224-Zn Co₁-950 are better.(2)The bimetallic imidazole MOFs were synthesized by a simpl e two-pot method and named as Ni/Co-ZIF-67.It can be judged by electron microscope that its structure is a sodalite cage structure.Test the XRD of Co-ZIF and Ni/Co-ZIF-67 respectively,it can be seen that the XRD peak is almost unchanged,and the metal content ratio in Ni/Co-ZIF-67 is also confirmed by ICP test.By testing the XRD of ZIF-67 and Ni/Co-ZIF-67 after seven days of immersion in water,it can be found that the structure of Co-ZIF has been completely destroyed,while the structure of Ni/Co-ZIF-67 has hardly changed.The stability of the bimetallic Ni/Co-ZIF-67 has been greatly improved.Then we used Ni/Co-ZIF-67 to catalyze the oxidative coupling reaction of tetrahydroquinoxaline and R-sodium sulfinate,and found that it has excellent catalytic performance.