Small organic molecules have special adsorption and reaction behaviors in the channels of various porous materials, such as zeolites, which determines the wide applications of these materials in catalysis, separation and energy storage. The host-guest interactions between small molecules and zeolite frameworks are the microscopic basis for the special properties and applications of these materials. The atomic-resolution observation of small-molecule configurations confined in zeolites using advanced electron microscopy can help us directly see different types of host-guest interactions, and then bring microscopic insight into the interaction sites and mechanisms. However, due to electron-beam damages and resolution limitations, imaging small organic molecules, which are sensitive to electron beam and composed of light elements, using electron microscopy has been full of challenges, especially the atomic single-molecule imaging, which is still a difficult Holy Grail in the field of electron microscopy. Therefore, the atomic-scale insight into molecular adsorption/desorption and host-guest interaction are still unrevealed in real space to date. In recent years, integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM) has brought new hope to this goal. Therefore, the recognition and understanding of molecular adsorption and desorption and host guest interaction, atomic scale and resolution still perplex researchers in related fields.
Recently, Prof. Boyuan Shen, in cooperation with Prof. Fei Wei and Dr. Xiao Chen of Tsinghua University, applies the iDPC-STEM and in-situ imaging technology into the direct observation of the adsorption/desorption behaviors and atomic configurations of pyridine and thiophene molecules in zeolite ZSM-5, breaking through the technical bottleneck that it is difficult for a single organic molecule to be imaged at the atomic level under electron microscope. The interaction mechanism between small molecules, such as pyridines and thiophenes, and acid sites of zeolites was really analyzed at the atomic level. The atomic coordinates obtained from intensity profile analysis are compared with the simulation results to figure out a configuration closest to the imaging results by using the least square fitting, so that the most probable position of acid site can be pointed out with atomic resolution. This work provides a general strategy for directly observing the configurations and interactions of these molecules in static images and in-situ experiments, and further extends the applications of ultra-high-resolution electron microscopy to the real-space study of a variety of single molecule behaviors. Relevant results were published online in Nature on July 13, 2022 (Nature, volume 607, pages 703–707 (2022)). Prof. Boyuan Shen is the first author of this paper.
Link to paper: https://www.nature.com/articles/s41586-022-04876-x
Title: Atomic imaging of zeolite-confined single molecules by electron microscopy
Authors: Boyuan Shen, Huiqiu Wang, Hao Xiong, Xiao Chen*, Eric G. T. Bosch, Ivan Lazić, Weizhong Qian, Fei Wei*
Acknowledgement: This work was supported by the National Key Research and Development Program of China (no. 2020YFB0606401), the National Natural Science Foundation of China (nos. 22005170, 21771029 and 202013981) and the National Key R&D Program of China (2017YFB0602204). We are grateful to the Tsinghua National Laboratory for Information Science and Technology for assistance with the energy simulation. B.S. is also thankful for the support from Suzhou Key Laboratory of Functional Nano & Soft Materials, Collaborative Innovation Center of Suzhou Nano Science & Technology, the 111 Project.
Editor: Danting Xiang, Jia Guo