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Zn 4 O clusters corresponding with those present in MOF-5, IRMOF-8, and IRMOF-9 have been synthesized as monounits with the respective monodentate organic linkers attached. Ultraviolet (UV) absorption analysis of synthesized clusters and metal organic frameworks (MOFs) reveals that the organic moieties in the MOFs lose their individual absorption and emission characteristics, in contrast with their subunits which retain these characteristics. Observed photoluminescence (PL) quantum yields of the MOFs are higher than those of their corresponding subunits. This is explained by the isolation of clusters in monounits, where linkers are only attached to one cluster, resulting in greater charge localization compared to MOFs. The photocatalytic activity of the clusters in the nonporous monounits crystals turned out to be higher than that of their MOF counterparts and that of zinc oxide in the oxidation of propene at room temperature under UV illumination. Clearly porosity does not offer in this case any significant advantage in contrast to charge localization at Zn 4 O clusters. This observed difference in photocatalytic activity was found to be inversely proportional to the difference in PL quantum yields between monounits and MOFs, highlighting competition between decay of excited states by photon emission and electron transfer. Detection of the same products of partial oxidation with similar selectivities for the crystals of the synthesized monounits as well as for the MOFs led to the conclusion that Zn 4 O clusters in the monounits are in fact photochemical equivalents of those in their corresponding MOFs.

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The use of the metal organic framework MIL-101(Cr) as support for Pt nanoparticles is evaluated in three selective hydrogenation reactions. Homogenous Pt nanoparticles of ∼4 nm can be formed inside the porosity of MIL-101(Cr) in close contact with the Cr trimers in an eggshell configuration by a wet impregnation procedure combined with sonication. The catalyst is applied in the selective hydrogenations of olefin mixtures, benzonitrile, and linoleic acid. In the case of an olefin mixture, 1-octene is selectively hydrogenated over 1-hexadecene, attributed to diffusion limitations that favor the hydrogenation of the smaller substrate. In the case of benzonitrile hydrogenation, benzylamine is selectively formed over dibenzylamine attributed to transition state selectivity. In the hydrogenation of linoleic acid, selectivities were similar to that for platinum on alumina.