Publications

Pairs of Brønsted acid protons were found in zeolite H,Na-Y
Angew. Chem. Int. Ed. 2018 , 57 ,14281 –14285
© HK

 

Two pairs of Brønsted acid sites have been identified in H,Na-Y zeolite, located in the supercage and in the sodalite cage, which upon ultrastabilization (dealumination) are transformed into pairs of Brønsted and Lewis acid sites. This mild postsynthetic modification step is an important process for converting this material into an active catalyst for large-scale commercial reactions. Pairing structures and their transformations have been investigated using 1H double-quantum NMR experiments for dehydrated zeolite, H,Na-Y, and its ultrastabilized form, H,Na-USY. This enables the detection of pairs of Brønsted and Lewis acid sites with unprecedented 1H resolution and distinguish them from isolated acid sites. The dealumination is also observed by static, ultrawideline 27Al solid-state NMR experiments.

 

  • Reviews

    • Koller, H., 7.3 Zeolites for Ion Exchange, Adsorption and Catalysis (invited book chapter), In: From Energy Storage  to Photofunctional Materials (Eds.: Pöttgen, R.; Jüstel, T.; Strassert, C.), De Gruyter, Berlin, Boston,  2023, pp. 279-303. 10.1515/9783110798890-018
    • Selectivities in Post-Synthetic Modification of Borosilicate Zeolites
      Hubert Koller, Cong-Yan Chen, and Stacey I. Zones Top. Catal. 58 (2015), 451-479.
      DOI: 10.1007/s11244-015-0382-0
    • Solid State NMR of Porous Materials - Zeolites and Related Materials (invited review),
      Hubert Koller and Mark Weiß, Top. Curr. Chem. 306 (2012), 189-227.
      DOI: 10.1007/128_2011_123
    • New Developments of NMR Spectroscopy Applied to Zeolite Catalysts
      Hubert Koller, Stud. Surf. Sci. Catal. 149 (2004), 105-122.
      DOI: 10.1016/S0167-2991(04)80758-4
    • The Dynamics of Hydrogen Bonds and Proton Transfer in Zeolites - Joint Vistas from Solid-State NMR and Quantum Chemistry
      Hubert Koller, Günter Engelhardt, Rutger A. van Santen, Top. Catal. 9 (1999), 163-180.
      DOI: 10.1023/A:1019131126634
    • 29Si NMR of Inorganic Solids
      Günter Engelhardt, Hubert Koller, NMR - Basic Principles and Progress 31 (1994), 1-29.
       DOI: 10.1007/978-3-642-50049-7_1

     

  • 2020 -

    • Park, Y.; Koller, H.; Lew, C.M.; Zones, S.I.; Davis, M.E., Correlating Local Geometry to 11B NMR Chemical Shift of Tetrahedrally Coordinated Boron in Molecular Sieves. J. Phys. Chem. C, 2024, accepted. 10.1021/acs.jpcc.4c02361
    • Koller, H.; Hunger, M., Response of Hydrogen-Bonded Brnsted Acid Sites in ZSM-5 to Adsorption and H\/D Exchange of Hydrocarbons. J. Phys. Chem. C, 2024, 128, 8974–8982. 10.1021/acs.jpcc.4c01199. (limited edition of free e-prints)
    • Lew, C.; Xie, D.; Jensen, K.; Schroeder, C.; Blaser, J.; Koller, H.; Zones, S., Use of Borosilicate Seeds to Synthesize Aluminosilicate SSZ-82, a Zeolite Containing Intersecting 12- and 10-Membered Ring Channels. Chem. Mater., 2023, 35,  6141-6151. 10.1021/acs.chemmater.3c01274
    • Koller, H., Zeolites for Ion Exchange, Adsorption and Catalysis (invited book chapter), In: From Energy Storage  to Photofunctional Materials (Eds.: Pöttgen, R.; Jüstel, T.; Strassert, C.), De Gruyter, Berlin, Boston,  2023, pp. 279-303.  10.1515/9783110798890-018
    • Schroeder, C.; Hansen, M.R.; Koller, H., Spatial Proximities Between Brønsted Acid Sites, AlOH Groups and Residual NH4+ Cations in Zeolites Mordenite and Ferrierite. J. Phys. Chem. C, 2023, 127, 736-745. 10.1021/acs.jpcc.2c07346. (limited edition of free e-prints)
    • Chen, Y.-F.; Schroeder, C.; Lew, C.M.; Zones, S.I.; Koller, H.; Sierka, M., Cooperativity of Silanol Defect Chemistry in Zeolites. PCCP, 2023, 25, 478-485. 10.1039/D2CP05218K
    • Schroeder, C.; Lew, C.M.; Zones, S.I.; Koller, H., Ordered Heteroatom Siting Preserved By B/Al Exchange in Zeolites. Chem. Mater. 2022, 34, 3479–3488. 10.1021/acs.chemmater.2c00359
    • Schroeder, C.; Zones, S. I.; Hansen, M.R.; Koller, H., Hydrogen Bonds Dominate Brønsted Acid Sites in Zeolite SSZ-42 – A Classification of Their Diversity. Angew. Chem. Int. Ed. 2022, 61, e202109313. 10.1002/anie.202109313
    • Schroeder, C.; Zones, S. I.; Mück-Lichtenfeld, C.; Hansen, M. R.; Koller, H., High Aluminum Ordering in SSZ-59: Residual 1H–27Al Dipolar Coupling Effects in 1H MAS NMR Spectra of Brønsted Acid Sites in Zeolites. J. Phys. Chem. C 2021, 125, 4869-4877. 10.1021/acs.jpcc.0c11379.
    • Grosso-Giordano, N. A.; Schroeder, C.; Xu, L.; Solovyov, A.; Small, D. W.; Koller, H.; Zones, S. I.; Katz, A., Characterization of a Molecule Partially Confined at the Pore Mouth of a Zeotype. Angew. Chem. Int. Ed. 2021, 60, 10239-10246. 10.1002/anie.202100166.
    • Schroeder, C.; Siozios, V.; Mück-Lichtenfeld, C.; Hunger, M.; Hansen, M. R.; Koller, H., Hydrogen Bond Formation of Bronsted Acid Sites in Zeolites. Chem. Mater. 2020, 32, 1564-1574. 10.1021/acs.chemmater.9b04714.
    • Schroeder, C.; Siozios, V.; Hunger, M.; Hansen, M. R.; Koller, H., Disentangling Bronsted Acid Sites and Hydrogen-Bonded Silanol Groups in High-Silica Zeolite H-ZSM-5. J. Phys. Chem. C 2020, 124, 23380-23386. 10.1021/acs.jpcc.0c06113.
    • Schroeder, C.; Mück-Lichtenfeld, C.; Xu, L.; Grosso-Giordano, N. A.; Okrut, A.; Chen, C. Y.; Zones, S. I.; Katz, A.; Hansen, M. R.; Koller, H., A Stable Silanol Triad in The Zeolite Catalyst SSZ-70. Angew. Chem. Int. Ed. 2020, 59, 10939-10943. 10.1002/anie.202001364.

     

  • 2010 - 2019

    • Schroeder, C.; Hansen, M. R.; Koller, H., Ultrastabilization of Zeolite Y Transforms Brønsted–Brønsted Acid Pairs into Brønsted–Lewis Acid Pairs. Angew. Chem. Int. Ed. 2018, 57, 14281-14285. 10.1002/anie.201808395.
    • Grosso-Giordano, N. A.; Schroeder, C.; Okrut, A.; Solovyoy, A.; Schöttle, C.; Chassé, W.; Marinkoyic, N.; Koller, H.; Zones, S. I.; Katz, A., Outer-Sphere Control of Catalysis on Surfaces: A Comparative Study of Ti(IV) Single-Sites Grafted on Amorphous versus Crystalline Silicates for Alkene Epoxidation. J. Am. Chem. Soc. 2018, 140, 4956-4960. 10.1021/jacs.7b11467.
    • Koller, H.; Uesbeck, T.; Hansen, M. R.; Hunger, M., Characterizing the First and Second 27Al Neighbors of Brønsted and Lewis Acid Protons in Zeolites and the Distribution of 27Al Quadrupolar Couplings by 1H{27Al} Offset REAPDOR. J. Phys. Chem. C 2017, 121, 25930-25940. 10.1021/acs.jpcc.7b09544.
    • Koller, H.; Senapati, S.; Ren, J. J.; Uesbeck, T.; Siozios, V.; Hunger, M.; Lobo, R. F., Post-Synthesis Conversion of Borosilicate Zeolite Beta to an Aluminosilicate with Isolated Acid Sites: A Quantitative Distance Analysis by Solid-State NMR. J. Phys. Chem. C 2016, 120, 9811-9820. 10.1021/acs.jpcc.6b01680.
    • Brunklaus, G.; Koller, H.; Zones, S. I., Defect Models of As-Made High-Silica Zeolites: Clusters of Hydrogen-Bonds and Their Interaction with the Organic Structure-Directing Agents Determined from 1H Double and Triple Quantum NMR Spectroscopy. Angew. Chem. Int. Ed. 2016, 55, 14459-14463. 10.1002/anie.201607428.
    • Koller, H.; Chen, C. Y.; Zones, S. I., Selectivities in Post-Synthetic Modification of Borosilicate Zeolites. Top. Catal. 2015, 58, 451-479. 10.1007/s11244-015-0382-0.
    • Dyballa, M.; Obenaus, U.; Lang, S.; Gehring, B.; Traa, Y.; Koller, H.; Hunger, M., Bronsted Sites and Structural Stabilization Effect of Acidic Low-Silica Zeolite A Prepared by Partial Ammonium Exchange. Micropor. Mesopor. Mater. 2015, 212, 110-116. 10.1016/j.micromeso.2015.03.030.
    • Senapati, S.; Zimdars, J.; Ren, J.; Koller, H., Post-Synthetic Modifications of As-Made Zeolite Frameworks Near The Structure-Directing Agents. J. Mater. Chem. A 2014, 2, 10470-10484. 10.1039/c4ta00656a.
    • Tong, H. T. T.; Koller, H., Control of Al for B framework substitution in zeolite Beta by counterions. Micropor. Mesopor. Mater. 2012, 148, 80-87. 10.1016/j.micromeso.2011.07.021.
    • Koller, H.; Weiß, M., Solid State NMR of Porous Materials: Zeolites and Related Materials. In Top. Curr. Chem., Chan, J. C. C., Ed. Springer: Berlin, 2012; Vol. 306, pp 189-227. 10.1007/128_2011_123.
    • Hould, N. D.; Senapati, S.; Koller, H.; Lobo, R. F., Effect of Al on Zeolite Beta Solid State Chemistry. Top. Catal. 2012, 55, 1332-1343. 10.1007/s11244-012-9914-z.
    • Ulke, S.; Koller, H., Microheterogeneity in phenyl group modified inorganic/organic hybrid gels after aerosol drying or slow solvent evaporation. Solid State Nucl. Magn. Reson. 2011, 39, 142-150. 10.1016/J.SSNMR.2011.03.005
    • Heimink, J.; Sieger, P.; Koller, H., Two-Dimensional pH Mapping of Release Kinetics of Silica-Encapsulated Drugs. J. Pharm. Sci. 2011, 100, 4401-4412. 10.1002/jps.22593.
    • Wichner, N. M.; Ghavtadze, N.; Wurthwein, E. U.; Koller, H., Imprinting With Phenyl Group Interactions: A Case Study of the Hybrid Sol-Gel Encapsulation of the Complex {Na[Ph2P(O)-CH2-P(O)Ph2]3}+ . Phys. Chem. C 2010, 114, 22590-22596. 10.1021/jp107581g.
    • Wichner, N. M.; Beckers, J.; Rothenberg, G.; Koller, H., Preventing sintering of Au and Ag nanoparticles in silica-based hybrid gels using phenyl spacer groups. J. Mater. Chem. 2010, 20, 3840-3847. 10.1039/c000105h.

     

  • 2000 - 2009

    • Lezhnina, M. M.; Jordan, E.; Klimin, S. A.; Lons, J.; Koller, H.; Mavrin, B. N.; Kynast, U., Fluoride Containing Guest Species in Alumosilicates: Tetrafluoroborate in the Sodalite Na8(Al6Si6O24)(BF4)2. Z. Anorg. Allg. Chem. 2009, 635, 450-455. 10.1002/zaac.200801112.
    • Paul, G.; Heimink, J.; Koller, H., Controlling drug release of sol-gel encapsulated Persantin and propranolol by surface interactions. Chem. Mater. 2008, 20, 5083-5089. 10.1021/cm8000267.
    • Paul, G.; Steuernagel, S.; Koller, H., Non-covalent interactions of a drug molecule encapsulated in a hybrid silica gel. Chem. Commun. 2007, 5194-5196. 10.1039/b711105c.
    • Koller, H.; Jordan, E.; Wilmer, D., Matrix effect on motional coupling and long-range transport of cations in zeolites. Angew. Chem. Int. Ed. 2007, 46, 3359-3362. 10.1002/anie.200605049.
    • Jordan, E.; Bell, R. G.; Wilmer, D.; Koller, H., Anion-promoted cation motion and conduction in zeolites. J. Am. Chem. Soc. 2006, 128, 558-567. 10.1021/ja0551887.
    • Bögershausen, A.; Pas, S. J.; Hill, A. J.; Koller, H., Drug release from self-assembled inorganic-organic hybrid gels and gated porosity detected by positron annihilation lifetime spectroscopy. Chem. Mater. 2006, 18, 664-672. 10.1021/cm051859o.
    • Wiebcke, M.; Bögershausen, A.; Koller, H., Hydrothermal synthesis, crystal structure and thermal behaviour of a zincoborophosphate, (H4TETA)1.5[Zn6B6P12O48] . 1.5H2O (TETA = triethylenetetraamine), with a chiral tetrahedral framework (CZP framework type). Microporous Mesoporous Mater. 2005, 78, 97-102. 10.1016/j.micromeso.2004.09.020
    • Koller, H.; Fild, C.; Lobo, R. F., Variable anchoring of boron in zeolite beta. Micropor. Mesopor. Mat. 2005, 79, 215-224. 10.1016/j.micromeso.2004.10.035.
    • Koller, H.; Kalwei, M., Studying ionic motion in tetrahydroxoborate sodalite by second moment analysis using Na-23{B-11} rotational echo double resonance data. J. Phys. Chem. B 2004, 108, 58-63. 10.1021/jp030536h.
    • Koller, H., An improved 1H NMR spectra interpretation of B and Al zeolites with dipolar methods. Recent Advances in the Science and Technology of Zeolites and Related Materials, Pts a - C 2004, 154, 1380-1384. 10.1016/S0167-2991(04)80653-0.
    • Koller, H., New developments of NMR spectroscopy applied to zeolite catalysts. Fluid Catalytic Cracking Vi: Preparation and Characterization of Catalysts 2004, 149, 105-122. 10.1016/S0167-2991(04)80758-4.
    • Jordan, E.; Koller, H., Cation dynamics in zeolites studied by MAS-NMR. Recent Advances in the Science and Technology of Zeolites and Related Materials, Pts a - C 2004, 154, 1555-1559. 10.1016/S0167-2991(04)80677-3
    • Barrett, P. A.; Boix, T.; Puche, M.; Olson, D. H.; Jordan, E.; Koller, H.; Camblor, M. A., ITQ-12: a new microporous silica polymorph potentially useful for light hydrocarbon separations. Chem. Commun. 2003, 2114- 2115. 10.1039/b306440a.
    • van Wüllen, L.; Koller, H.; Kalwei, M., Modern solid state double resonance NMR strategies for the structural characterization of adsorbate complexes involved in the MTG process. PCCP 2002, 4, 1665-1674. 10.1039/b108999b.
    • Kalwei, M.; Koller, H., Quantitative Comparison of REAPDOR and TRAPDOR Experiments by Numerical Simulations and Determination of H–Al Distances in Zeolites. Solid State Nucl. Magn. Reson. 2002, 21, 145-157. 10.1006/snmr.2002.0055.
    • Villaescusa, L. A.; Barrett, P. A.; Kalwei, M.; Koller, H.; Camblor, M. A., Synthesis and Physicochemical Characterization of an Aluminosilicate Zeolite with IFR Topology, Prepared by the Fluoride Route. Chem. Mater. 2001, 13, 2332-2341. 10.1021/cm001180e.
    • Koller, H.; Kalwei, M.; Fild, C.; Lobo, R. F.; Camblor, M. A.; Villaescusa, L. A.; van Wüllen, L., 13-O-01-Where are the acid sites in zeolites? A novel NMR approach to measure B/Al ordering around structure directing agents. In Stud. Surf. Sci. Catal., Galarneau, A.; Fajula, F.; Di Renzo, F.; Vedrine, J., Eds. Elsevier: 2001; Vol. 135, p 182. 10.1016/S0167-2991(01)81341-0.
    • Kentgens, A. P. M.; Iuga, D.; Kalwei, M.; Koller, H., Direct Observation of Bronsted Acidic Sites in Dehydrated Zeolite H-ZSM5 Using DFS-Enhanced 27Al MQMAS NMR Spectroscopy. J. Am. Chem. Soc. 2001, 123, 2925-2926. 10.1021/ja005917c.
    • Camblor, M. A.; Barrett, P. A.; Diaz-Cabanas, M. J.; Villaescusa, L. A.; Puche, M.; Boix, T.; Perez, E.; Koller, H., High silica zeolites with three-dimensional systems of large pore channels. Microporous Mesoporous Mater. 2001, 48, 11-22. 10.1016/S1387-1811(01)00325-0.
    • Shantz, D. F.; Schmedt a.d. Günne, J.; Koller, H.; Lobo, R. F., Multiple-Quantum 1H MAS NMR Studies of Defect Sites in As-Made All-Silica ZSM-12 Zeolite. J. Am. Chem. Soc. 2000, 122, 6659-6663. 10.1021/ja000374s.
    • Fild, C.; Shantz, D. F.; Lobo, R. F.; Koller, H., Cation-induced transformation of boron-coordination in zeolites. Phys. Chem. Chem. Phys. 2000, 2, 3091-3098. 10.1039/b002134m.
    • Shantz, D.F.; Lobo, R.F.; Fild, C.; Koller, H., Controlling the distribution of framework aluminum in high-silica zeolites. Stud. Surf. Sci. Catal. 2000, 130, 845-850. 10.1016/S0167-2991(00)81064-2
    • Fild, C.; Eckert, H.; Koller, H., Charge-induced partial ordering of boron around structure directing agents in zeolites observed by C-13{B-11} rotational echo double resonance NMR. J. Am. Chem. Soc. 2000, 122, 12590-12591. 10.1021/ja005609e.
    • Cho, H. H.; Kim, S. H.; Kim, Y. G.; Kim, Y. C.; Koller, H.; Camblor, M. A.; Hong, S. B., Synthesis and characterization of gallosilicate molecular sieves with high gallium contents: Examples of structure direction exerted by gallium. Chem. Mater. 2000, 12, 2292-2300. 10.1021/cm0001051.

     

  • 1990 - 1999

    • Wirnsberger, G.; Fritzer, H. P.; Koller, H.; Behrens, P.; Popitsch, A., Intermolecular interactions of inorganic and organic molecules embedded in zeolite-type materials probed by near-infrared Fourier transform Raman spectroscopy. J. Mol. Struct. 1999, 481, 699-704. 10.1016/S0022-2860(98)00725-X.
    • Shantz, D. F.; Fild, C.; Koller, H.; Lobo, R. F., Guest-Host Interactions in As-made Al-ZSM-12: Implications for the Synthesis of Zeolite Catalysts. J. Phys. Chem. B 1999, 103, 10858-10865. 10.1021/jp992549u.
    • Overweg, A. R.; Koller, H.; de Haan, J. W.; van de Ven, L. J. M.; van der Kraan, A. M.; van Santen, R. A., Ferrocene and dicarlbonylcyclopentadienylcobalt in faujasite-type zeolites: A study of molecular motion. J. Phys. Chem. B 1999, 103, 4298-4308. 10.1021/jp984517x.
    • Koller, H.; Wölker, A.; Villaescusa, L. A.; Diaz-Cabanas, M. J.; Valencia, S.; Camblor, M. A., Five-coordinate silicon in high-silica zeolites. J. Am. Chem. Soc. 1999, 121, 3368-3376. 10.1021/ja9840549.
    • Koller, H.; Engelhardt, G.; van Santen, R. A., The dynamics of hydrogen bonds and proton transfer in zeolites - joint vistas from solid-state NMR and quantum chemistry. Top. Catal. 1999, 9, 163-180. 10.1023/A:1019131126634.
    • Engelhardt, G.; Kentgens, A. P. M.; Koller, H1997.; Samoson, A., Strategies for extracting NMR parameters from Na-23 MAS, DOR and MQMAS spectra. A case study for Na4P2O7. Solid State Nucl. Magn. Reson. 1999, 15, 171-180. 10.1016/S0926-2040(99)00054-5.
    • Fild, C.; Eckert, H.; Koller, H., Evidence for selective association of tetrahedral BO4 units with Na+ and of trigonal BO3 units with H+ in dehydrated zeolite B-ZSM-5 from solid-state NMR spectroscopy. Angew. Chem. Int. Ed. 1998, 37, 2505-2507. 10.1002/(SICI)1521-3773(19981002)37:18<2505::AID-ANIE2505>3.0.CO;2-F
    • Koller, H.; Wölker, A.; Eckert, H.; Panz, C.; Behrens, P., Five-coordinate silicon in zeolites: Probing SiO4/2F- sites in nonasil and ZSM-5 with Si-29 solid-state NMR spectroscopy. Angew. Chem. Int. Ed. 1997, 36, 2823-2825. 10.1002/anie.199728231.
    • Koller, H.; Overweg, A. R.; van Santen, R. A.; de Haan, J. W., C-13 and Na-23 solid-state NMR study on zeolite Y loaded with Mo(CO)6. J. Phys. Chem. B 1997, 101, 1754-1761. 10.1021/jp962791q.
    • Koller, H.; Overweg, A. R.; van de Ven, L. J. M .; de Haan, J. W.; van Santen, R. A., Mechanisms of molecular motion of Mo(CO)6 in zeolites NaY and HY from C-13-NMR lineshapes. Microporous Mater. 1997, 11, 9-10.1016/S0926-2040(97)80141-517. 10.1016/S0927-6513(97)00026-6.
    • Koller, H.; Meijer, E. L.; van Santen, R. A., 27Al Quadrupole Interaction in Zeolites Loaded With Probe Molecules - A Quantum-Chemical Study of Trends in Electric Field Gradients and Chemical Bonds in Clusters. Solid State Nucl. Magn. Reson. 1997, 9, 165-175. 10.1016/S0926-2040(97)00056-8.
    • Koller, H., Scientific biography of Dr. Günter Engelhardt. Solid State Nucl. Magn. Reson. 1997, 9, Ix-+. 10.1016/S0926-2040(97)80141-5
    • Koller, H.; Lobo, R. F.; Burkett, S. L.; Davis, M. E., SIO...HOSI Hydrogen-Bonds in As-Synthesized High-Silica Zeolites. J. Phys. Chem. 1995, 99, 12588-12596. 10.1021/j100033a036.
    • Koller, H.; Engelhardt, G.; Felsche, J., VARIABLE-TEMPERATURE H-1, NA-23, AND SI-29 MAS NMR-STUDIES ON SODIUM-SILICATE HYDRATES OF COMPOSITION NA2O.SIO2.nH2O (n=9, 6, 5) - LOCAL-STRUCTURE IN CRYSTALS, MELTS, SUPERCOOLED MELTS, AND GLASSES. Z. Anorg. Allg. Chem. 1995, 621, 301-310. 10.1002/zaac.19956210217.
    • Koller, H.; Burger, B.; Schneider, A. M.; Engelhardt, G.; Weitkamp, J., Location of Na+ and Cs+ cations in CsNaY zeolites studied by Na-23 and Cs-133 magic-angle spinning nuclear magnetic resonance spectroscopy combined with X-ray structure analysis by Rietveld refinement. Microporous Mater. 1995, 5, 219-232. 10.1016/0927-6513(95)00061-5.
    • Koller, H.; Engelhardt, G.; Kentgens, A. P. M.; Sauer, J., 23Na NMR Spectrocopy of Solids - Interpretation of Quadrupole Interaction Parameters and Chemical Shifts. J. Phys. Chem. 1994, 98, 1544-1551. 10.1021/j100057a004.
    • Engelhardt, G.; Koller, H., 29Si NMR of Inorganic Solids. In Solid-State NMR II: Inorganic Matter, Blümich, B., Ed. Springer Berlin Heidelberg: Berlin, Heidelberg, 1994; pp 1-29. 10.1007/978-3-642-50049-7_1.
    • Engelhardt, G.; Hunger, M.; Koller, H.; Weitkamp, J., Exploring Cation Siting in Zeolites by Solid-State NMR of Quadrupolar Nuclei. In Stud. Surf. Sci. Catal., Weitkamp, J.; Karge, H. G.; Pfeifer, H.; Hölderich, W., Eds. Elsevier: 1994; Vol. 84, pp 421-428.23. 10.1016/S0167-2991(08)64141-5.
    • Camblor, M. A.; Lobo, R. F.; Koller, H.; Davis, M. E., Synthesis and Characterization of Zincosilicates with the Sod Topology. Chem. Mater. 1994, 6, 2193-2199. 10.1021/cm00047a046.
    • Wiebcke, M.; Grube, M.; Koller, H.; Engelhardt, G.; Felsche, J., Structural Links between Zeolite-Type and Clathrate Hydrate-Type Materials - Redetermination of the Crystal-Structure of [N(CH3)4]8[Si8O20].65H2O by Single-Crystal X-Ray-Diffraction and Variable-Temperature MAS NMR Spectroscopy. Microporous Mater. 1993, 2, 55-63. 10.1016/0927-6513(93)80062-Y.
    • Hunger, M.; Engelhardt, G.; Koller, H.; Weitkamp, J., Characterization of Sodium-Cations in Dehydrated Faujasites and Zeolite Emt by 23Na DOR, 2D Nutation, and MAS NMR. Solid State Nucl. Magn. Reson. 1993, 2, 111-120. 10.1016/0926-2040(93)90029-M.
    • Wiebcke, M.; Koller, H., Single-Crystal X-Ray-Diffraction and Variable-Temperature MAS NMR Study on the Heterogeneous Network Clathrate Na[N(CH3)4]7[Si8O20].54H2O. Acta Crystallogr. B 1992, 48, 449-458. 10.1107/S0108768192001149.
    • Engelhardt, G.; Koller, H.; Sieger, P.; Depmeier, W.; Samoson, A., Al-27 and Na-23 double-rotation NMR of sodalites. Solid State Nucl. Magn. Reson. 1992, 1, 127-135. 10.1016/0926-2040(92)90013-Y.
    • Engelhardt, G.; Koller, H., A Simple Procedure for the Determination of the Quadrupole Interaction Parameters and Isotropic Chemical-Shifts from Magic Angle Spinning Nmr-Spectra of Half-Integer Spin Nuclei in Solids. Magn. Reson. Chem. 1991, 29, 941-945. 10.1002/mrc.1260290914.
    • Koller, H.; Engelhardt, G.; Felsche, J., 29Si NMR Studies of the Transformation of Silicate Anions in the System Na2O.SiO2.nH2O (n=9,5) in Crystals, Melts, and Solution. J. Chem. Soc. Chem. Commun. 1990, 371-372. 10.1039/c39900000371.

     

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