Real-Time Imaging and Quantitative Evolution for Pyrolysis of Carbon Dots-Encapsulated Metal-Organic Frameworks at the Nanoscale by In Situ Environmental Transmission Electron Microscopy

The pyrolysis of metal-organic frameworks (MOF)has beenwidely used approach to generate hierarchical structures with thecorresponding metal, metal carbide, or metal oxide nanoparticles embeddedin a porous carbon matrix with a high specific surface area for industrialcatalysis, energy storage and transfer, etc. MOF-derived heterogeneouscatalysts can be constructed by the encapsulation of carbon dots (CDs)with plenty of hydroxyl and amine groups to enhance the performanceof the final product. Controlled formation of metallic carbon structuresat the nanoscale, especially matter cycling and transformation onthe nanoscale interface, is important for the production of industrialcatalysts as well as the research of materials science and engineeringprogress. However, the mass transfer at the nanoscale during the processingof MOF pyrolysis remains less understood due to the lack of directobservation. Herein, by using in situ environmental transmission electronmicroscopy, real-time imaging and quantitative evolution of porouscarbon decorated with metal species by the pyrolysis of CDs-encapsulatedzeolitic imidazolate framework-67 are achieved. The migration of Co,the flow of aggregates, and the growth of carbon nanotubes observedin the nanoscale pyrolysis laboratory working at 600 & DEG;C withan air atmosphere are present. Experimental studies based on reductionand oxidation reaction models reveal that the synergistic effect betweendoped graphite nitrogen and confined Co nanoparticles is beneficialfor boosting catalytic performance.

Automated summary

The pyrolysis of MOFs is a widely used method to generate hierarchical structures with metal nanoparticles embedded in a porous carbon matrix. In this study, in situ environmental transmission electron microscopy was used to observe the real-time formation and evolution of porous carbon decorated with metal species during the pyrolysis of zeolitic imidazolate framework-67 encapsulated with carbon dots. The migration of cobalt, the flow of aggregates, and the growth of carbon nanotubes were observed at the nanoscale. Experimental studies revealed the synergistic effect between doped graphite nitrogen and confined cobalt nanoparticles for enhanced catalytic performance.