Recently, it has been reported that scientific achievements of users of the China Spallation Neutron Source's General Powder Diffraction Instrument have been published in Nature. The research team utilized neutron diffraction, three-dimensional electron diffraction, synchrotron powder X-ray diffraction, aberration-corrected scanning transmission electron microscopy, and solid-state nuclear magnetic resonance techniques to determine the fine structure of three-dimensional stable ultra-large molecular sieves. This research breakthrough surpasses the limits of traditional molecular sieve crystallization theory.
Led by Chinese Academy of Sciences academicians and professors Yu Jihong and Chen Feijian from Jilin University, along with Professor Wu Peng from East China Normal University and researcher Li Jian from Nanjing University, the domestic research team collaborated with Professor Miguel A. Camblor from the Materials Research Institute in Madrid, Spain. They successfully synthesized an example of a three-dimensional stable ultra-large pore molecular sieve ZEO-5 with a 20 × 16 × 16 ring channel system using the interlinking method. This achievement once again refreshes the record for the pore size of stable fully connected ultra-large pore molecular sieves.
Basic characterization of ZEO-4 and ZEO-5 and the pore system and pore size of ZEO-5. Image provided by the China Spallation Neutron Source.
Zeolites are crystalline microporous aluminosilicates widely used as catalysts, adsorbents, and ion exchangers in traditional chemical engineering, environmental applications, as well as emerging fields like energy storage, optoelectronic devices, biomedical sciences, fuel cells, and biomass conversion. Zeolite molecular sieves with superlarge pore structures are in great demand for industrial applications involving the catalytic conversion and adsorptive separation of large molecules. The synthesis of three-dimensional stable superlarge pore molecular sieves has long been a major challenge in the field of zeolite synthesis.
The structure of the successfully synthesized ZEO-5 superlarge pore molecular sieve by the research team contains two unprecedented tension-bearing double-four-ring (triple-four-ring) topologies, a structure previously unseen in zeolite molecular sieves. This sieve possesses a superlarge unit cell and a composition of light elements, posing significant challenges for structural determination. Neutron diffraction technology, with its high resolution and sensitivity to light elements, has provided a crucial tool for deciphering this complex structure.
Benefiting from the wide d-spacing detection range, high resolution, and good signal-to-noise ratio of the general powder diffractometer at the China Spallation Neutron Source, the research team successfully obtained more accurate information on bond lengths and bond angles through precise analysis of neutron diffraction, three-dimensional electron diffraction, and synchrotron powder X-ray diffraction data. Combined with aberration-corrected scanning transmission electron microscopy and solid-state nuclear magnetic resonance techniques, the authenticity of the superlarge triple-four-ring structure was verified.
This research breakthrough surpasses the theoretical limits of traditional zeolite crystallization theory, overturns the inherent understanding of zeolite hydrothermal synthesis, and further demonstrates that the structure construction of three-dimensional stable superlarge pore molecular sieves, which was difficult to achieve via traditional hydrothermal synthesis, can be realized based on new reaction mechanisms. This work provides new insights and directions for the development of zeolite materials and holds significant scientific and practical value.
Related paper information: https://doi.org/10.1038/s41586-024-07194-6
