Molecular sieves have been widely used in the fields like petrochemistry, coal utilization, pollution abatement, energy conservation, and pharmaceuticals. They could be synthesized under hydrothermal condition with the participation of water at a certain temperature and pressure.
When molecular sieves are applied in industrial processes, they always confront the environment of water vapor atmosphere at elevated temperature. However, the effect of hydrothermal conditions on the molecular sieve framework remains unclear.
Recently, Prof. WEI Yingxu, Prof. XU Shutao and Prof. LIU Zhongmin from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences revealed a water-induced structural dynamic and reversible breakage-bonding of T-O-T bonds in molecular sieves framework under mild hydrothermal conditions (100-300 ℃).
The study was published in Angew. Chem. Int. Ed. on July 24.
The encapsulation strategy of TMP and pyridine into CHA cavities under mild hydrothermal conditions and their further applications for acidity characterization and catalyst modification.(Image by SUN Tantan and XU Shutao)
The scientists incorporated 17O atoms from H217O vapor into the framework of an industrial MTO catalyst SAPO-34 molecular sieve, and confirmed that the dynamic and reversible T-O-T bonds breakage-bonding happened.
They encapsulated two bulky probe molecules, trimethylphosphine (TMP) and pyridine with much larger kinetic diameters than the 8-MR pore size of SAPO-34 into chabazite (CHA) cavities by the dynamic and reversible breakage-bonding of T-O-T bonds under mild hydrothermal conditions.
They proposed ship-in-a-bottle strategy based on above findings and it opened new fields for fine acidity identification and give extra boost in shape selective catalysis.
The study was supported by the National Natural Science Foundation of China, the Key Research Program of Frontier Sciences of CAS, the International Partnership Program of CAS, the Youth Innovation Promotion Association of CAS and Liaoning Revitalization Talents Program. (Text by SUN Tantan and XU Shutao)