198 Topics in Current Chemistry Editorial Board: A. de Meijere KN ...

Functional Organic Zeolite Analogues
Yasuhiro Aoyama
Institute for Fundamental Research of Organic Chemistry, Kyushu University, Hakozaki,
Higashi-ku, Fukuoka 812–8581, Japan. E-mail: aoyamay@ms.ifoc.kyushu-u.ac.jp
CREST, Japan Science and Technology Corporation
There is much current interest in organic solid hosts, whose guest-binding properties are
reminiscent of traditional inorganic zeolites. The basic design strategy is to assemble organic
and metal-ion building blocks into a network by using directional intermolecular interactions
such as hydrogen bonding and coordination. The network structures can be controlled by the
geometrical and topological properties of the building blocks. When free from interpenetration,
the resulting networks afford cavities or channels (occupying, in some cases, as much as
60–70% of the total volume) capable of selective guest binding. Some coordination and
multiply hydrogen-bonded networks are robust enough to withstand the removal of included
guests, thus sustaining as large as 10 Å guest-free channels. Less robust hydrogen-bonded
networks undergo a transition to more dense structures upon guest removal; they are, however,
flexible enough to readsorb the guests and restore the single-crystal structures of the
host-guest adducts. Guest exchange also occurs, during which crystallinity is retained.
Another important consequence of host-guest complexation is activation of trapped guests.
Facilitated intracavity reactions, coupled with dynamic guest-binding behaviours (exchange
of products and reactants as guests), suggest a potential use of the present type of microporous
organic and metal-organic solids as catalysts. This is in fact demonstrated for the
Diels-Alder and related ene reactions. The present stage of functional organic zeolite analogues
and the problems and prospects associated therewith are discussed from both static and
dynamic viewpoints.
Keywords: Zeolite analogue, Microporous material, Network, Pore, Catalysis.
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
2 Static Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
2.1 Molecular Networks Using Supramolecular Building Blocks . . . . . 133
2.2 Symmetry-Controlled 3D Nets . . . . . . . . . . . . . . . . . . . . . 134
2.3 Layered 2D Nets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
2.4 Interaction-Supported Channels . . . . . . . . . . . . . . . . . . . . 142
2.5 Modes of Guest Binding . . . . . . . . . . . . . . . . . . . . . . . . . 147
2.6 Selectivities and Pore Size Control . . . . . . . . . . . . . . . . . . . 148
3 Dynamic Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
3.1 Robust Networks and Maintenance of Permanent Voids . . . . . . . 150
3.2 Flexible Networks and Induced-Fit Adjustment . . . . . . . . . . . . 151
3.3 Apohosts and Guest-Binding Selectivities . . . . . . . . . . . . . . . 153
Topics in Current Chemistry, Vol. 198
© Springer Verlag Berlin Heidelberg 1998