Incorporation of Other Metal Complexes

Ethylenediamine is a common aliphatic chain chelate, and it forms very stable chelating compounds with a variety of transition metals. Howe and Lunsford incorporated Con-ethylenediamine complex into zeolites X and Y to form composite compounds that can adsorb oxygen.11731 In both zeolite cages the oxygen adduct [Con])(en)202]2+ may be formed, and this complex adduct is stable up to 70 °C in the presence of oxygen. The ESR parameters of the adduct are similar to those for the adduct in solution. 

The structures and compositions of microporous crystals are becoming more versatile, and this has laid foundations for incorporation of complexes with various structures and functionalities in microporous crystals. The previously reported complex incorporation was mainly limited to the use of zeolites as the hosts. The aluminophosphate microporous 

It is also of significance to incorporate complex molecules into microporous crystals to form photochemically or photophysically active centers. Because of the separation by the host framework, the complexes located in the channels or cages of microporous crystals are isolated. If the isolated centers with oxidation or reduction features are loaded in the connected and adjacent cages of a microporous crystal, redox pairs may be formed. Electron transfer may occur on these redox pairs under the excitation of light, and therefore photochemical reactions may proceed effectively. This is important for the utilization of solar energy. In addition, this type of assembly system may also be used to simulate the electron transfer process of oxidation-reduction in biological systems. 

Apart from forming catalysts for photochemical reactions, some rare-earth ion complexes may also form efficient luminescent materials after incorporation into microporous crystals. Alvaro et al. loaded a europium complex into zeolite Y,111831 mordenite, and ZSM-5. Because of their confinement in the zeolite framework, the chance for the luminescent centers to decay nonradiationally is reduced, and as a result the lifetime is increased in comparison with that in solution. In the meantime, upon formation of the complex, the luminescence intensity of Eu3+ ion is distinctly increased. Therefore, it is possible to prepare valuable composite luminescent materials using microporous crystals as hosts and complexes as guests. 

The frameworks of inorganic porous materials are usually rigid, and the framework atoms do not react with guest molecules under normal conditions. Therefore, the channels and cages of porous materials may be ideal templates for the formation of complexes that have shapes and sizes matching the channels and cages. Some complex 

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