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Zeolites were used as templates to prepare microporous polymer replicas. Phenol−formaldehyde polymers were synthesized and cured within the channel networks of zeolites Y, β, and L. Dissolution of the aluminosilicate framework in aqueous HF yields an organic replica that contains

Cadmium telluride nanoclusters were prepared by vapor-phase deposition of elemental tellurium in Na+−zeolite A, followed by partial exchange of the zeolite with aqueous Cd(NO3)2, and reduction with hydrogen at 450 °C. The stability of the nanoclusters in environments that normally cause rapid Ostwald ripening or oxidation (air, water, and Br2/MeOH) was greatly enhanced by exchanging the Na+−zeolite with K+ after the Te0 deposition and hydrogen reduction steps. Exchange of K+ for Na+ narrows the effective pore diameter of zeolite A from 4.0 to 3.3 A, inhibiting the diffusion of larger atoms, ions, and molecules (Te0, Te2-, and Br2). Distinct absorption maxima in diffuse reflectance UV−visible spectra and sharp exciton peaks in low-temperature excitation spectra verified the presence of quantum-confined CdTe. These spectral features are largely unchanged when the material, in its K+-exchanged form, is exposed to air and water for periods of months. Under the same conditions, materials in the Na+ form are ra...

Layered alkali-metal titanates (Na[sub 2]Ti[sub 3]O[sub 7] and K[sub 2]Ti[sub 4]O[sub 9]), niobates (KNb[sub 3]O[sub 8] and K[sub 4]Nb[sub 6]O[sub 17]), and titanoniobates (KTiNbO[sub 5] and CsTi[sub 2]NbO[sub 7]) were internally platinized, acid-exchanged, sensitized with ruthenium polypyridyl complexes, and studied as photocatalysts for the production of H[sub 2] and I[sub 3][sup [minus]] from acidic alkali-metal iodide solutions. The titanates were inactive as photocatalysts, whereas the niobates and titanoniobates were active with quantum efficiencies up to 0.3% for HI photolysis with visible light. Calculations based on electronegativity showed that the conduction band edge potentials of the acid-exchanged titanates were too positive to prevent semiconductor-mediated recombination of photogenerated H[sub 2] and I[sub 3][sup [minus]]. Laser flash photolysis/transient diffuse reflectance spectra established that iodide reduces the oxidized sensitizer, forming I[sub 2][sup [sm bullet][minus]], which subsequently decays in a bimolecular reaction to form I[sub 3][sup [minus]]. The inefficiency of HI photolysis can be attributed to charge recombination between I[sub 3][sup [minus]] and conduction band electrons for the niobates and titanoniobates. 29 refs., 16 figs., 1 tab.

Photoinduced electron transfer and energy transfer reactions of tris(2,2[prime]-bipyridyl)ruthenium(II) (Ru(bpy)[sub 3][sup 2+]) with methylviologen (MV[sup 2+]) and tris(2,2[prime]-bipyridyl)osmium(II) (Os(bpy)[sub 3][sup 2+]) ion-exchanged onto/into separate zeolite Y particles were studied by emission spectroscopy. The kinetics of interparticle exchange were probed by observing the quenching of the MLCT excited state of-Ru(bpy)[sub 3][sup 2+] by mobile MV[sup 2+] or OS(bpy)[sub 3][sup 2+] ions. The exchange reactions occur on time scales of seconds to hours, depending on the ionic strength of the surrounding medium. The time-dependent luminescence data were fitted to a dispersed kinetics model, from which average rate constants for the exchange reactions could be extracted. Time constants for interparticle exchange of MV[sup 2+] and Os(bpy)[sub 3][sup 2+] ions, in the range 10[sup 3]-10[sup 5] s at electrolyte concentrations of 0.1-3 mM, are significantly longer than the time scales (10[sup [minus]7]-10[sup 1] s) of most electrochemical and photochemical intrazeolitic reactions involving these and similar electroactive ions. These results argue for reaction mechanisms that invoke intrazeolite electron transfer, rather than exchange of electroactive ions followed by solution-phase electron transfer, in these systems. 25 refs., 6 figs., 1 tab.