Recently, Dr. Peng Guo and the team led by Academician Zhongmin Liu at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, synthesized a stable novel large-pore aluminophosphate molecular sieve, DNL-11, using commercial templating agents based on their understanding of the structure and synthesis of molecular sieves. They directly resolved the crystal structure of DNL-11 using three-dimensional electron diffraction techniques. The related findings were published in the "Journal of the American Chemical Society."
Aluminophosphate molecular sieves are composed of interconnected phosphorus oxide tetrahedra and aluminum oxide tetrahedra sharing oxygen vertices, featuring regular pore or cage structures. These materials not only serve as the basis for further research on aluminosilicate and metalloaluminophosphate molecular sieves but also play crucial roles as catalyst supports and adsorbents. The performance of aluminophosphate molecular sieves is closely related to their crystal structure. Typically, the crystal size of molecular sieves falls within the submicron or even nanometer range, making precise structural analysis challenging with traditional X-ray single-crystal diffraction methods, which has somewhat limited the development of molecular sieves.
Schematic Representation of "DNL-11" Molecular Sieve. Dalian Institute of Chemical Physics.
Researchers, through advanced characterization techniques, have understood the mechanism of structure-directing agents in known molecular sieves and applied it to the design and synthesis process of molecular sieves. The team synthesized a novel topology of molecular sieve named "DNL-11" by using commercial structure-directing agents. Furthermore, the team utilized three-dimensional electron diffraction and PXRD refinement techniques to elucidate and refine the structure of DNL-11, directly determining its crystal structure and the positioning of the structure-directing agents. It was found that DNL-11 possesses one-dimensional 16-ring ultra-large channels, where the structure-directing agents are arranged in two intersecting columns and assembled via π-π stacking interactions. All structure-directing agents are protonated and interact with oxygen atoms on the framework.
Additionally, the team demonstrated that DNL-11 can maintain structural stability at temperatures as high as 1000°C and exhibits excellent water adsorption performance in extremely low humidity environments (humidity = 5%).
Related Paper Information: https://doi.org/10.1021/jacs.4c01393
