中国科学院大连化学物理研究所70周年所庆学术报告（28）

报告时间：2019年8月22日（星期四）下午14:00

报告地点：能源楼（A座）一楼会议室

报告人：韩宇教授，沙特阿拉伯国王科技大学

　　报告摘要：

　　High-resolution imaging of electron beam-sensitive crystalline materials, such as zeolites and metal-organic frameworks, is one of the most difficult applications of transmission electron microscopy (TEM). The challenges are manifold, including the acquisition of images with an extremely low beam dose, the time-constrained search for crystal zone axes, the precise alignment of successive images, and the accurate determination of the defocus value.

　　We reported that using a direct-detection electron-counting camera, it is possible to acquire useful high-resolution TEM images with electron dose as low as a few electrons per square angstrom to ensure that the intact structure was captured before damage occurred. Later, we reported a suite of new methods that we recently developed to address the rest challenges mentioned above. Our methods advance the HRTEM of extremely beam-sensitive materials from “occasionally possible” to “routine”. We demonstrate the effectiveness of our methodology by capturing atomic-resolution TEM images of several metal organic frameworks (MOFs) that are generally recognized as highly sensitive to electron beams. In the case of MOF UiO-66, individual metal atomic columns, various types of surface termination, and benzene rings in the organic linkers, are clearly identified. We also successfully apply our methods to other electron beam-sensitive materials, and achieve atomic-resolution TEM imaging of the organic-inorganic hybrid perovskite CH3NH3PbBr3 for the first time.  More recently, we applied this new technology to prove the successful encapsulation of single molecule magnets in MOF NU-1000, and to investigate the evolution and transformation of various defects in MOF UiO-66, and to probe the subtle differences in the surface structure between various MOF MIL-101 samples. We also report a new TEM specimen preparation technique particularly useful for beam-sensitive materials.

　　At the end of the my talk, I will present our recent work on imaging atomically dispersed Mo in the 10-MR microporous channels of ZSM-5, which is an important catalyst for methane dehydroaromatization (MDA) reaction and how the understanding from high-resolution imaging helps to design a long-life MDA catalyst.

　　报告人简介：

　　Dr Han is a materials chemist and his research is focused on nanoporous and nanostructured materials, including ordered mesoporous materials, hierarchically structured zeolites, porous organic polymers, porous carbons, and metallic plasmonic nanocrystals. His ability to precisely control the structure and morphology of these materials promoted his great success in developing novel applications for them in gas adsorption/separation, heterogeneous catalysis, and nanophotonics. Dr. Han also has expertise in electron microscopy and electron tomography, using which he has successfully solved or identified some complex nanostructures. Dr. Han has published>180 research articles in prestigious journals including Science, Nature, Nature Materials, Nature Chemistry, Nature Nanotechnology, Nature Catalysis, Nature Communications, JACS, and these papers have been cited over 16,000 times with h-index of 62. His achievements have garnered international recognition. In 2004, he was named as a TR100 Young Innovator by the Massachusetts Institute of Technology’s magazine of innovation, Technology Review. In 2006, he was awarded the Young Scientist Award by the Singapore National Academy of Science. In 2016, he got the Cheung Kong Scholar award, the highest academic award issued to an individual in higher education by the Ministry of Education of the People's Republic of China.

　　联系人：人事处、科技处