A series of mixed-metal NH 2-UiO-66(Zr/Ti) with different percentages of exchanged Ti have been prepared and studied by transient absorption spectroscopy (TAS). The photo-generated transients from mixed NH 2-UiO-66(Zr/Ti) exhibit at short time scales two defined absorption bands, evolving to a continuous absorption band expanding from 300 nm to 700 nm at longer time scales. The observed spectral changes are compatible with an initial formation of Ti 3+-O-Zr 4+ and its further transformation to Ti 4+-O-Zr 3+ via metal-metal electron exchange, thus, providing support to the role of substituted Ti as mediator to facilitate electron transfer from excited ligand to the (Zr/Ti) 6 O 4 (OH) 4 nodes in mixed NH 2-UiO-66(Zr/Ti). The slow recombination of photo-generated electrons and holes in the mixed NH 2-UiO-66(Zr/Ti) has been advantageously used for the construction of a photovoltaic cell fabricated with the mixed NH 2-UiO-66(Zr/Ti), reaching higher photon-to-current efficiency than NH 2-UiO-66(Zr).

Ruthenium(II) bis(2,2′-bipyridine) (2,2′-bipyridyl-5,5′-dicarboxylic acid), Rudcbpy, attached to the UiO-67(Zr) metal organic framework (MOF), generates upon visible light excitation the localized triplet excited state of the ruthenium(II) bipyridyl complex that decays partly to a very long-lived (millisecond time scale) photoinduced charge-separated state following a similar behavior as that of analogous ruthenium(II) tris(bipyridyl) complex dissolved in water, except that the lifetime of the soluble complex excited state is orders of magnitude shorter. The occurrence of photoinduced charge separation on the Rudcbpy-UiO-67(Zr) MOF has been proven visually by using methyl viologen as electron acceptor. Rudcbpy-UiO-67(Zr) behaves as a heterogeneous, reusable, photoredox catalyst promoting debromination of α-bromoketones with excellent selectivity at high conversions. Characterization data show that Rudcbpy-UiO-67(Zr) is stable under the photocatalytic reaction conditions.

Graphenes as metal-free catalysts for the oxidative depolymerization of lignin modelsJuan F. Blandez, [b] Sergio Navalón, [b] Mercedes Alvaro, [b] and Hermenegildo Garcia* [a] Abstract: Graphene oxide promotes the oxidative degradation of guaiacylglycerol-β-guaiacyl ether, a lignin model compound, in different solvents including acetonitrile, toluene and water mainly to guaiacol, 2-methoxyquinone, vanillic acid and coniferyl aldehyde.Reduced graphene oxide and B-doped graphene exhibit similar activity as graphene oxide. Control experiments indicate that metal impurities should play a marginal role in the observed catalytic activity.