Zeolite collapse and polyamorphism

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Zeolites are microporous crystalline materials with diverse industrial applications.
• Understanding structural transitions like collapse is crucial for material stability and performance.
• Polyamorphism, the existence of multiple amorphous phases, plays a key role in zeolite structural changes.

Purpose of the Study:

• To outline the phenomenology of zeolite collapse.
• To investigate the role of polyamorphism in destabilizing zeolite structures.
• To characterize the structural and dynamic changes during zeolite collapse.

Main Methods:

• Synchrotron X-ray diffraction experiments.
• Computer simulations of low-density cage structures (e.g., zeolite A, zeolite Y).
• Magic angle spinning Nuclear Magnetic Resonance (NMR) spectroscopy.
• Inelastic X-ray scattering (IXS).
• Inelastic neutron scattering (INS).

Main Results:

• Polyamorphism is identified as a key factor in destabilizing zeolitic structures.
• Transitions between ordered, disordered, and amorphous phases are observed.
• Significant differences in entropy and density exist between polyamorphic phases and the precursor zeolite.
• Changes in structural order and mechanical rigidity are highlighted by NMR and IXS.
• Two-level systems, detected by INS, are linked to the dynamics of zeolite cage collapse.

Conclusions:

• Zeolite collapse is a complex process involving polyamorphism and phase transitions.
• The study provides insights into the structural and dynamic mechanisms governing zeolite collapse.
• Understanding these phenomena is essential for designing stable and functional zeolite materials.