Karl Seff, Professor Emeritus
Department of Chemistry
University of Hawai’i at Manoa
2545 McCarthy Mall
Honolulu, HI 96822-2275
Phone: (808) 226-7917
Fax: (808) 956-5908
Email: Karl Seff
Office: Bilger 235
Karl Seff received his B.S. degree from the University of California at Berkeley in 1959 and his Ph.D. from the Massachusetts Institute of Technology in 1964. After three years of post-doctoral work at U.C.L.A., he joined the faculty of the chemistry department at the University of Hawaii. In 1988-89, he spent a year in Oxford, England studying pulsed-neutron diffraction from zeolite powders. His efforts in X-ray and neutron crystallography are directed mostly at the determination of the structures of chemically modified zeolites, to identify new species synthesized in intrazeolitic voids.
Research InterestsA novel chemistry is observable crystallographically within the rigid porous anionic aluminosilicate frameworks of variously ion- exchanged, desolvated and chemically treated zeolites. The ions D+, Na+, K+, Rb+, Cs+, Tl+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+ have been found at positions of extreme coordinative unsaturation, which is the very basis of many of the valuable properties that activated zeolites have, such as selective sorption and catalysis. Intrazeolitic redox processes involving Cu and Ag have been observed simply upon desolvation, in the latter case to give the new molecule hexasilver, Ag6 (no charge), the smallest possible fully developed single crystal of silver (see figure). These can also be prepared by the reduction of Ag+ with Cs(g) or Rb(g). By the sorption of metal vapors, the following species were synthesized within zeolites and seen for the first time crystallographically: (Na5)4+, (K3)2+, (K4)3+, (Rb3)+, (Rb3)2+, (Cs4)3+, Cd+, (Cd2)2+, and Cd2. More interestingly, the zeolite sometimes begins to fill with vapor metal atoms to give, not small isolated clusters, but positively charged two- or three- dimensional continua, with formulae like (Cs122)86+ per unit cell. The properties of these cationic continua, which appear to be a new class of metals or semi-metals, remain to be established. In addition, small molecules sorbed by desolvated (activated) zeolites have been found complexed to cations within zeolite A. Some of those molecules are C2H2, C2H4, C3H6, NO, NO2, CO, CH3OH, Cl2, Br2, CS2 and H2S. We believe that the new molecules N3H5 (triazane) and N3H3 (cyclotriazane) have been synthesized and are stabilized within the zeolite by complexation to Ag+. In other work, linear (Pb-S-Pb)2+ ions were found in zeolite Y, and near cubic (Pb7O(OH)3)9+ ions were found in zeolite A. Atoms of Ar and Kr have been found encapsulated in partially Cs+-exchanged zeolite A. Ca2+,Ag+-zeolite A was exposed to Cs(g) at 250 ºC: for reasons of Cs atom size and Ag+ cation immobility, we observed the quantitative intrazeolitic reduction of Ca2+ to Ca while Ag+ remained entirely unreacted! To make possible the preparation of many new zeolite compositions, we are seeking to identify non-aqueous solvents which may be used for ion exchange.
Nanoclusters of Ag4I4 in the Sodalite Cavities of Zeolite A. The following short paper will be published in the Proceedings of the Fourteenth International Zeolite Conference to be held in Capetown South Africa in April, 2004. It announces the discovery that elements can disproportionate in a very interesting way upon sorption into a zeolite. This has become a major new research theme in my group.
- Kim, C.W.; Jung, K.J.; Heo, N.H.; Kim, S.H.; Hong, S.B.; Seff, K., Crystal Structures of Vacuum-Dehydrated Ni2+-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni2+, Ni8O4•xH2O8+, x ≤ 4, Clusters with Near Cubic Ni4O4 Cores, and H+. J. Phys. Chem. C 2009, 113, 5164-5181.
- Heo, N.H.; Kim, C.W.; Kwon, H.J.; Kim, G.H.; Kim, S.H.; Hong, S.B.; Seff, K., Detailed Determination of the Tl+ Positions in Zeolite Tl-ZSM-5. Single-Crystal Structures of Fully Dehydrated Tl-ZSM-5 and H-ZSM-5 (MFI, Si/Al = 29). Additional Evidence for a Nonrandom Distribution of Framework Aluminum. J. Phys. Chem. C 2009, 113, 19937-19956.
- Lim, W.T.; Seo, S.M.; Wang, L.; Lu, G.Q.; Heo, N.H.; Seff, K. Single-Crystal Structures of Highly NH4+ Exchanged, Fully Deaminated, and Fully Tl+ Exchanged Zeolite Y (FAU, Si/Al = 1.56), All Fully Dehydrated. Microporous Mesoporous Mater 2010, 129, 11-21