Zeolite mimics

Multiple hydrogen bonding interactions in tetrahedral building blocks have been employed by the group of Wuest to produce a remarkable tailored porous zeolite mimic, dubbed an organic zeolite because it does not contain any inorganic components at all.104 The pore-forming material is based on... 

The interactions of a reagent with a zeolite are governed by the shape-selective properties and the confinement effects previously mentioned. The cavities and pores of a zeolite can be considered as microreactors, containing stabilized active sites, which can be designed to have particular properties. This is comparable to the active site of an enzyme, where the catalytic activity depends on the three-dimensional arrangement of the functional groups on the side-chains of the amino acids of the protein. Several of these zeolite mimics of enzyme action have been developed, and three are worthy of mention here. 

Soldatov. D.V. Ripmeester. J.A. Inclusion in microporous P-bis( 1,1,1 -trifluoro-5,5-dimethyl-5-methoxyacetylaceto-nato)copper(II), an organic zeolite mimic. Chem. Mater. 

Catalysis - Porous three-dimensional networks can be viewed as zeolite mimics and can exhibits similar properties in some cases. The enclosed environment within charmels, akin to zeolites (Section 4.2) and discrete capsules (see Chapter 3, Section 3.5), can provide novel reactivity or catalytic ability and can be size- and shape-selective. Coordination polymers offer an advantage over traditional zeolites in that chiral channels are able to be constructed by using chiral ligands. 

Encapsulated Cu—chlorophthalocyanines oxidize hexane at C-l using 02 and at C-2 using H202 as oxidants. The dimeric structure of copper acetate is intact when it is incorporated into the zeolite. This is a regioselective aromatic hydroxylation catalyst, which mimics the specificity of the monooxygenase enzyme tyrosinase.82,89 Zeolite NaY catalysts made with a tetranuclear Cu(II) complex were synthesized and characterized.90... 

The FePcY-PDMS supramolecular catalyst resembles the architecture of natural enzymes. In this system the PDMS membrane takes over the role of the phospholipid double layer likewise, the zeolite imitates the protein and the FePc complex the Fe-protoporphyrin. Zeolite-encaged Cu-histidine complexes were also studied as mimics of natural Cu-enzyme complexes.173... 

N. Herron, Toward Si-based hfe Zeolites and enzyme mimics, Chemtech 19, 542-548 (1989). 

This work prompted a flurry of activity in the mid- to late 1980s to find the type IM isotherm. A number of inventions can be found in which alumina, or silica gel are blended with zeolites type X or Y to mimic the shape of the isotherm that Collier defined. Mol Sieve type DDZ-70(g) is in fact one of only a few true type IM isotherms. This product and Engelhard s type ETS-10 both have the required isotherm shape for water and deliver the benefits expected, to wit excellent capacity for water, self-sharpening mass transfer zone and low energy investment required to regenerate. Mol Sieve type DDZ-70(g) is used commercially in rotors... 

Zeolites seem to be promising catalysts for the conversion of fine chemicals and organic intermediates [1-3]. Metallo-phthallocyanines encaged in zeolites Y have been proposed as enzyme mimics [4-7]. Zeolites can replace the protein portion of natural enzymes and modify the reactivity in the same way as enzymes do by imposing steric constraints on the environment of the active metal ion site. 

In the present work, the construction of a mimic of cytochrome P-450 is attempted by in situ synthesis of iron-phthallocyanines in the supercages of zeolite Y and in the channels of VPI-5. Its catalytic activity and selectivity is tested in the oxyfunctionalization of n-alkanes with tertiary butyl hydroperoxide. 

Robust inorganic porous networks such as zeolites are of tremendous industrial interest in separation, storage and catalysis. As a result they have stimulated the preparation of a wider range of organic zeolites that aim to mimic their porous and robust properties while allowing more extensive synthetic tenability. 

A FePc complex encaged in the zeolite Y supercages, in its turn, can be wrapped in a polydimethylsiloxane membrane, thus acting not only as a mechanistic but also as a formal mimic of Cytochrome P450 often found in cell membranes.[57] Such membranes, contacted on one side with substrate and on the other side with oxidant, catalyse oxygenation reactions in a membrane reactor in the absence of any solvent, the majority of the product amount being recovered from the more polar phase. 

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