Alcohols (bioalcohols) is a class of chemicals that are used as a feedstock for the manufacturing of a large number of valuable intermediates in industrially important processes. Currently, sustainable technologies for selective conversion of alcohols utilize “green” oxidants, mainly, ambient air or oxygen. Due to the high affinity of oxygen towards silver, the latter serves as an active component of supported heterogeneous catalysts. In this review, we consider Ag-based catalysts that participate in gas- or liquid-phase oxidation of alcohols. Oxidation of methanol, ethanol, ethylene glycol, propylene glycol, glycerol, benzyl and allyl alcohols is mostly considered. A particular attention is paid to selective photooxidation of alcohols over Ag-based catalysts. We discuss the catalyst composition in terms of (1) the state of the active component, (2) the nature of the substrate, (3) support nature, and (4) the strength of the metal–support interactions.

The nature of organic linker substituents plays an important role in gas sorption and separation as well as in catalytic applications of metal–organic frameworks. Zirconium-based UiO-66 is one of the most tunable members of this class of materials. However, the prediction of its properties is still not a fully solved problem. Here, the infrared spectroscopic measurements using highly sensitive CO probe molecules, combined with DFT calculations, are used in order to characterize the performance of different acidic sites caused by the presence of different organic linker substituents. The proposed model allowed differentiation between various active sites over the UiO-66 and clarification of their behavior. The experimental IR bands related to CO adsorption can be unambiguously assigned to one type of site or another. The previously undescribed highly red-shifted band is attributed to CO adsorbed on coordinatively unsaturated zirconium sites through an O atom. The results confirm the lower and higher Lewis’s acidity of coordinatively unsaturated Zr sites on linker defects in the UiO-66 structure when electron-withdrawing and electron-donating groups are, respectively, included in a terephthalate moiety, whilst the Brønsted acidity of zirconium oxo-cluster remains almost unchanged.

Different methods (the wetness impregnation of Ag and Pd precursors dissolved in water or acetonitrile solution, and the double solvent impregnation technique) were employed to immobilize Ag–Pd nanoparticles (NPs) into the pores of the microporous zirconium-based metal-organic framework known as UiO-66. The obtained materials were characterized by using nitrogen adsorption-desorption at −196 °C, powder X-ray diffraction, UV-Vis diffusion reflectance spectroscopy, and transition electron microscopy measurements. Special attention was paid to the acid and redox properties of the obtained materials, which were studied by using temperature-programmed desorption of ammonia (TPD-NH₃) and temperature-programmed reduction (TPR-H₂) methods. The use of a drying procedure prior to reduction was found to result in metallic NPs which, most likely, formed on the external surface and were larger than corresponding voids of the metal-organic framework. The formation of Ag–Pd alloy or monometallic Ag and Pd depended on the nature of both metal precursors and the impregnation solvent used. Catalytic activity of the AgPd/UiO-66 materials in propylene glycol oxidation was found to be a result of synergistic interaction between the components in AgPd alloyed NPs immobilized in the pore space and on the external surface of UiO-66. The key factor for consistent transformation of propylene glycol into lactic acid was the proximity between redox and acid-base species.