The team of Cross-scale Porous Material Research Center, Institute of Advanced Interdisciplinary Studies, Chongqing University, published a research paper titled “Imaging defects and their evolution in a  l–organic  work at sub-unit-cell resolution” in Nature Chemistry (a sub-journal of Nature, with latest factor of influence of 26.20), in collaboration with well-known foreign colleges and universities on May 13, 2019. Researchers of the Center are first co-authors of the paper.

Figure: Comparison of Uio-66 Local Structure

UiO-66 is one of the most widely studied MOF materials at present. It has characteristics including chemical stability and catalytic activity. Previous studies have indicated that the outstanding performance is due to the defect structure of MOF material. The HRTEM has atomic resolution, and is able to directly observe the structural defect in real spaces. However, MOF materials have high structural sensitivity. As a result, the bombardment of a great number of electron beams would easily damage its feature structure. As such, traditional HRTEM technology is not suitable for study of MOF spatial structure. In addition, given existence of organic ligands, higher requirements are being placed on resolution and contract of stereoscan photographs.

In the research, the newest low-dose HRTEM technology was used in combination with the electron crystallography to observe the defect type, structure, distribution and its evolution behavior in the Uio-66 structure on the unit cell scale. The research indicated that there were two types of defects in Uio-66 structure, namely, ligand defect and metal cluster defect. The concentration of the two in the structure can be regulated effectively by controlling the synthesis condition; catalysis test results indicated that the metal cluster defect had better catalytic activity than ligand defect in the Lewis acid catalyzed reaction.

In the research, unique technological means was used for high-resolution imaging of local defect structure in MOF structure, and offered all-new thoughts on application of electron technology in characterization of MOF sensitive materials. Furthermore, it offered more straight-forward research approaches for structure-function relationship of nano-micron structure functional materials.

Link of the paper: https://www.nature.com/articles/s41557-019-0263-4