Preparation Of MOFs-based Materials And Their Photocatalytic Reduction And Electrocatalytic Reduction Properties

Metal-organic frameworks(MOFs)are a type of crystalline porous material with a periodic network structure formed by connecting inorganic metal centers and bridging organic ligands through self-assembly.They have controllable pore size distribution,high specific surface area and adjustable performance.They are also excellent precursors for carbon-based catalysts,which can be widely applied in high-efficienct electrocatalysts and photocatalysts.In this dissertation,based on the structural characteristics of MOFs,two kinds of catalysts were successfully prepared through linker modification and MOFs-heteroatom modification.They can be applied to photocatalytic CO₂ reduction and electrocatalytic O₂ reduction,respectively.A simple ultrasonic synthesis method was used to prepare two-dimensional amorphous a Cu-DHTP nanosheets.In order to adjust the composition of the ligand,terephthalic acid(H₂BDC)and2,5-hydroxyterephthalic acid(H₂DHTP)were used as the ligand respectively.In a gas-solid photocatalytic CO₂ reduction system without any cocatalyst or sacrificial agents,under simulated sunlight radiation,the yield of CO was 10.55?mol·g^-1·h^-1 and a high selectivity was?100%.Besides,a Cu-DHTP showed good stability and durability.The excellent catalytic performance of a Cu-DHTP in the gas-solid photocatalytic system is due to the synergistic effect of the amorphous MOF nanosheets and the highly active coordination unsaturated sites derived from H₂DHTP.This work successfully extended the application of two-dimensional amorphous MOF to the photocatalytic reduction of CO₂,providing a new idea for the design and development of a more effective MOF-based photocatalytic CO₂reduction system.By pyrolyzing the mixture of Co-Zn-MOFs nanosheets and dicyandiamide,the catalysts Co@CNTs-T(T=600?700?800?900oC)with a three-dimensional network structure of N-doped carbon nanotubes embedded with Co nanoparticles were successfully prepared.Due to the nanotube structure,the optimally prepared Co@CNTs-800 catalyst exhibits rapid charge transfer and ion diffusion.The carbon layer coated on the Co nanoparticles is beneficial to enhancing the stability of the oxygen reduction(ORR)electrocatalyst.In addition,there are more defects due to the volatilization of zinc and the introduction of nitrogen.Therefore,the optimally Co@CNTs-800catalyst exhibits excellent ORR electrochemical activity(0.85 V vs.RHE)and excellent stability.