Synthesis of Discrete CHA Zeolite Nanocrystals without Organic Templates for Selective CO2 Capture

• Published in: Angewandte Chemie International Edition Vol. 59; no. 52; pp. 23491 - 23495
• Main Authors: Debost, Maxime, Klar, Paul B., Barrier, Nicolas, Clatworthy, Edwin B., Grand, Julien, Laine, Fabien, Brázda, Petr, Palatinus, Lukas, Nesterenko, Nikolai, Boullay, Philippe, Mintova, Svetlana
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 21-12-2020
• Edition: International ed. in English
• Subjects: Aluminosilicates; Aluminum; Aluminum silicates; Carbon dioxide; Carbon sequestration; Cations; CO2 adsorption; Crystal structure; Crystals; Electron diffraction; Energy requirements; in situ PXRD; Molecular structure; Nanocrystals; nanozeolites; precession-assisted 3D ED; Selectivity; Silicon; Storage capacity; Structural stability; Synthesis; template-free synthesis; Unit cell; Zeolites
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202009397

Small‐pore zeolites such as chabazite (CHA) are excellent candidates for the selective separation of CO2; however, the current synthesis involves several steps and the use of organic structure‐directing agent (OSDA), increasing their cost and energy requirements. We report the synthesis of small‐pore zeolite crystals (aluminosilicate) with CHA‐type framework structure by direct synthesis in a colloidal suspension containing a mixture of inorganic cations only (Na+, K+, and Cs+). The location of CO2 molecules in the host structure was revealed by 3D electron diffraction (3D ED). The high sorption capacity for CO2 (3.8 mmol g−1 at 121 kPa), structural stability and regenerability of the discreate CHA zeolite nanocrystals is maintained for 10 consecutive cycles without any visible degradation. The CHA zeolite (Si:Al=2) reaches an almost perfect CO2 storage capacity (8 CO2 per unit cell) and high selectivity (no CH4 was adsorbed).
The synthesis of nanosized CHA‐type zeolite without organic structure‐directing agents is presented. The zeolite material exhibits excellent CO2 storage capacity, high stability under high‐temperature treatment, and selectivity towards CO2 over CH4, controlled by Cs+ in the host structure. The environmentally benign and energy‐efficient synthesis of CHA nanocrystals is more affordable than reported methods.