Perspective on the Use of Ultrasonic Monitoring for In Situ Diagnostics of Zeolite and MOF Crystallization

The investigationand understanding of the underlying mechanismsfor the crystallization of molecular sieve materials, such as metal-organicframeworks (MOFs) and zeolites, have received increasing interestin recent years. This is mainly because improvements of the correspondingequipment were made that are essential for in situ diagnostics. Incontrast to classical techniques, such as X-ray diffraction and neutronscattering, nuclear magnetic resonance, or infrared and Raman spectroscopy,ultrasonic monitoring has not received proper attention. Thereby,especially for zeolites, important insights have been gained withthis technique already. However, for MOFs, the number of publicationsdealing with in situ US monitoring is still limited. Therefore, thisperspective gives an overview of the topic of in situ monitoring ofcrystallization of zeolites and MOFs and highlights the work thathas been done so far by ultrasonic monitoring. Furthermore, we statebenefits and current challenges for further establishing ultrasonicmonitoring as a tool for the investigation of crystallization processes. Ultrasound diagnostics is one of themost versatile andflexible tools for the investigation of particle syntheses. Due toits compact and robust design, monitoring of US velocity and US attenuationis useful in the lab as well on the industrial scale for investigatingzeolite and MOF syntheses.

Automated summary

The investigation of the underlying mechanisms for the crystallization of MOFs and zeolites has gained increasing interest, with improvements in in situ diagnostic equipment. Ultrasonic monitoring, though overlooked compared to classical techniques, has provided important insights, particularly for zeolites. However, its use for MOFs is limited. This perspective provides an overview of in situ monitoring of crystallization and highlights the work done using ultrasonic monitoring for zeolites and MOFs, along with the benefits and challenges of establishing it as a tool for investigating crystallization processes.