© Hubert Koller

Zeolites – nanoporous materials with tailored reaction environments

Our scientific work is dedicated to the investigation of porous materials with solid state NMR spectroscopy. Zeolites are porous aluminosilicates, and they belong to the most important inorganic materials with enormous relevance in applications. Zeolites are important as catalysts and functional materials in many applications. Our main interest is on interactions at interfaces, nanostructured materials, sol-gel processes, self-assembly phenomena and pore design.

The figures show two different situations with Brønsted acid sites in zeolites. The top figure shows a pair of such acid sites in the large cage (supercage) of zeolite Y. The conversion of such a Brønsted- Brønsted pair to a Brønsted- Lewis pair is achieved by selective dealumination. This leads to one of the most important commercial zeolite catalysts. This conversion of the local structure of acid sites was investigated with special 1H solid state NMR methods, which are based on the homonuclear dipolar interaction. The figure at the bottom shows a Brønsted acid site in a hydrogen bond in zeolite ZSM-5. The focus of our interest here is the spectroscopic identification of such H-bonded acid sites and their catalytic properties in comparison with acid sites with no H-bonding.

Relevant preliminary work:

  1. A Stable Silanol Triad in The Zeolite Catalyst SSZ‐70
    Koller H, Schroeder C, Mück-Lichtenfeld C, Xu L, Grosso-Giordano N A, Okrut A, Chen C, Zones S I, Katz A, Hansen M R. Angew. Chem.
    Int. Ed.  (2020) Accepted
  2. Hydrogen Bond Formation of Brønsted Acid Sites in Zeolites
    Schroeder C, Siozios V, Mück-Lichtenfeld C, Hunger M, Hansen M H, Koller H. Chem. Mater. 32, 4, 1564-1574 (2020)
  3. Ultrastabilization of Zeolite Y Transforms Brønsted–Brønsted Acid Pairs into Brønsted–Lewis Acid Pairs
    Schroeder C, Hansen M R, Koller H. Angew. Chem. Int. Ed. 57, 14281 –14285 (2018)
  4. Outer-Sphere Control of Catalysis on Surfaces: A Comparative Study of Ti(IV) Single-Sites Grafted on Amorphous versus Crystalline Silicates for Alkene Epoxidation
    Grosso-Giordano N A, Schroeder C, Okrut A, Solovyov A, Schottle C, Chassé W, Marinkovic N, Koller H, Zones S I, Katz A. J. Am. Chem. Soc. 140, 4956-4960 (2018)
  5. Characterizing the First and Second 27Al Neighbors of Bronsted and Lewis Acid Protons in Zeolites and the Distribution of 27Al Quadrupolar Couplings by 1H{27Al} Offset REAPDOR
    Koller H, Uesbeck T, Hansen M R, Hunger M. J. Phys. Chem. C 121, 25930–25940 (2017)
  6. Defect Models of As-Made High-Silica Zeolites: Hydrogen Bond Clusters and Their Interaction with the Organic Structure-Directing Agents Determined from 1H Double and Triple Quantum NMR Spectroscopy
    Brunklaus G, Koller H,  Zones S I. Angew. Chem. Int. Ed. 55, 14459-14463 (2016)
  7. Selectivities in Post-Synthetic Modification of Borosilicate Zeolites
    Koller H, Chen C -Y, Zones S I. (Review) Top. Catal. 58, 451-479 (2015)