CO2 and H2O Sorption Induced Bulk-Phase Changes of CALF-20 Captured Using In Situ Laboratory X-ray Powder
Sebastian Bette1, Anastasia Sleptsova1, Bettina V Lotsch1,2
1Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
Journal of the American Chemical Society
|July 11, 2025
Summary
Calgary Framework 20 (CALF-20), a metal-organic framework, demonstrates stable carbon dioxide and water adsorption, making it ideal for CO2 sequestration. Its structural dynamics under gas loading were investigated using X-ray powder diffraction.
Area of Science:
- Materials Science
- Chemistry
- Environmental Science
Background:
- Metal-organic frameworks (MOFs) are investigated for carbon capture.
- Calgary Framework 20 (CALF-20) is a zinc oxalate and triazolate-based MOF.
- CALF-20 shows stability in CO2 and water adsorption/desorption cycles.
Purpose of the Study:
- To investigate the structural dynamics of CALF-20 during CO2 and H2O adsorption/desorption.
- To understand the CO2 breathing mechanism and water uptake behavior.
- To demonstrate the utility of laboratory X-ray powder diffraction for MOF studies.
Main Methods:
- In situ high-resolution laboratory X-ray powder diffraction (XRPD).
- Systematic study of CO2 and H2O adsorption and desorption.
- Variable temperature experiments (-70 °C to 60 °C).
Main Results:
- CALF-20 exhibits significant structural dynamics (breathing) upon CO2 loading, altering pore shape.
- CO2 uptake at -70 °C follows a core-shell mechanism with strong binding.
- Two distinct hydrated phases of CALF-20 were identified, with water loading independent of temperature (25-60 °C).
Conclusions:
- CALF-20 is a promising material for industrial-scale CO2 sequestration due to its cycling stability.
- Advances in XRPD enable detailed, accessible investigation of MOF structural dynamics.
- Understanding MOF breathing behavior is crucial for optimizing gas adsorption applications.
