University of Houston • University of Houston-Clear Lake • ISSO Annual Report Y2002—pp. 89-90

Nano-Structure Open-Framework Materials For Nanofibers

Jack Y. Lu (UHCL)

SYNTHESIS AND FABRICATION OF FUNCTIONAL MATERIALS represent one of the great challenges in current research. Microporous metal-organic polymers have found a wide range of technological applications such as molecular separation and pollution prevention in air, liquid, and water systems, where they can be used as ion exchangers and molecular sieves. These novel zeolitelike materials may be fabricated into nanofibers. One of the key factors in the success of fabricating metal-organic nanomaterials is the synthesis of desirable metal-organic polymers that can be suited for the fabrication of nanomaterials. Exploration in this project is designed to produce novel microporous metal-organic polymers desirable for the generation of metal-organic nanofibers.

Experimental Activity, Results, and Discussion
Among the new metal-organic polymers synthesized in our laboratory, {[Cu₂(IN)₃]·I₅^-·5/6I₂·H₂O}_¥ (IN: isonicotinato)¹ is an unusual polyiodide inclusion metal-organic polymer with a novel 3-D nano hollow-channel open-framework synthesized via an oxidation reaction route under hydrothermal conditions. The diameter of the channel is about 1.15 nm (Fig. 1), slightly smaller than that of carbon nanotubes (~1.4 nm).

Figure 1. View of the different shape of channels in the structure

[Cd(NA)₂]² (NA = nicotinato), a new three-dimensional (3-D) neutral coordination polymer, has been synthesized under hydrothermal reaction conditions. The structure consists of distorted square pyramidal cadmium centers coordinated by two independent nicotinato ligands. One nicotinato ligand is tridentate, and the other one is bidentate to cadmium metal centers. Every two cadmium atoms are bridged by two carboxylato groups of the tridentate nicotinato ligands through O(2) and O(4) atoms to form a binuclear cadmium unit: Cd₂(NA)₄. The O(4) atom is at the apical site while the two pyridyl groups and the other two oxygen atoms are at the equatorial positions. The formation of the binuclear units created eight-member rings, which were then linked by nicotinato ligands to result in large 24-member rings. There are four eight-member rings on each 24-member ring: two eight-member rings at trans-position to each other are perpendicular to the other two eight-member rings. Four 24-member rings connect to each eight-member ring, via covalent bonding to the binuclear cadmium centers: two 24-member rings are perpendicular to the other two 24-member rings (Fig. 2). The propagation of the 24-member rings and eight-member rings extends to three directions resulting in a 3-D open framework structure.

Figure 2. View of the perpendicular 24-member rings.
One parallel 24-member ring is omitted for clarity.

Acknowledgments
We appreciate the financial support provided by ISSO. This work made use of MRSEC/TCSUH Shared Experimental Facilities supported by the National Science Foundation and the Texas Center for Superconductivity at the University of Houston.

References
¹J. Y. Lu and V. Schauss. "A Novel Nanostructured Open-Channel Coordination Polymer with an Included Fused-Polyiodide Ring," Eur. J. Inorg. Chem. (2002): 1945-47.
²J. Y. Lu and E. E. Kohler. "A Non-Interpenetrating 3-D Coordination Polymer Built from Binuclear Cd Units Elaborated with Square Pyramidal Geometry of Cadmium," Inorg. Chem. Commun. 5 (2002): 196-98.

Publications
Lu, J. Y. and A. M. Babb. "An Extremely Stable Open-Framework Metal-Organic Polymer With Expandable Structure and Selective Adsorption Capability," Chem. Commun. (2002): 1340.
Lu, J. Y. and A. M. Babb. "The First Triple-Layer 2-D Coordination Polymer: [Cu₃(bpen)(IN)₆(H₂O)₂]," Inorg. Chem. 40 (2001): 3261.
Lu, J. Y. and A. M. Babb. "A New 3-D Neutral Framework Coordination Polymer Constructed via Square Pyramidal Binuclear Cu(II) and Nicotinato-Ligand," Inorg. Chem. Commun. 4 (2001): 716.
Lu, J. Y. and A. M. Babb. "Self-Assembly of Two-Dimensional Coordination Polymers with Rigid and Flexible Building Blocks," Inorg. Chim. Acta 318 (2001): 186.
Lu, J. Y. and A. M. Babb. "A Simultaneous Reduction, Substitution and Self-Assembly Reaction Under Hydrothermal Conditions A fforded the First Diiodopyridine Copper(I) Coordination Polymer," Inorg. Chem. 41 (2002): 1339.
Lu, J. Y. and A. M. Babb. "An Unprecedented Interpenetrating Structure With Two Covalent-Bonded Open-Framework of Different Dimensionality," Chem. Commun. (2001): 821.
Lu, J. Y. and E. E. Kohler. "A New 2-D Chiral Coordination Polymer of [Zn(nicotinate)2]n." Inorg. Chem. Commun. 5 (2002): 600.
Lu, J. Y. and E. E. Kohler. "A Non-Interpenetrating 3-D Coordination Polymer Built From Binuclear Cd Units Elaborated With Square-Pyramidal Geometry of Cadmium," Inorg. Chem. Commun. 5 (2002): 196.
Lu, J. Y. and J. Macias. "An Unprecedented Tetrahedral Zinc Mutual-Face-Insertion Coordination Polymer With Both Covalent and Double-Hydrogen Bonding Interactions," CrystEngComm 4 (2002): 17.
Lu, J. Y. and K. A. Runnels. "An Unprecedented Mixed-Valent-Copper Metal-Organic Polymer Displaying Graphite-Like Properties," Inorg. Chem. Commun. 4 (2001): 678.
Lu, J. Y. and V. Schauss. "Crystal Engineering of A Three-Dimensional Coordination Polymer Based on Both Covalent and O-H·O···Hydrogen Bonding Interactions of Bi-functional Ligand," CrystEngComm (2001): 26.
Lu, J. Y. and V. Schauss. "A Novel Nanostructured Open-Channel Coordination Polymer With an Included Fused-Polyiodide Ring," Eur. J. Inorg. Chem. (2002): 1945.
Lu, J. Y., A. L. Reynolds, and K. A. Runnels. "A New Metal-Organic Structure with Alternating One-Dimensional Serpentine Ribbon Chains and Two-Dimensional Layer Networks of Different Topology," CrystEngComm (2001): 34.
Lu, J. Y., K. A. Runnels, and C. Norman. "A New Metal-Organic Polymer with Large Grid Acentric Structure Created by Unbalanced Inclusion Species and Its Electrospun Nanofibers," Inorg. Chem. 40 (2001): 4516.
Lu, J. Y., C. Norman, K. A. Abboud, and A. Ison. "Crystal Engineering of An Inclusion Coordination Polymer With Cationic Pocket-Like Structure and Its Property to Form Metal-Organic Nanofibers," Inorg. Chem. Commun. 4 (2001): 459.
Lu, J. Y., T. J. Schroeder, A. M. Babb, and M. Olmstead. "Two New Coordination Polymers Differentiated by C-H···O Hydrogen Bonding," Polyhedron 20 ( 2001): 2445.

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