Catalysis drives the conversion of substrates to the wanted products under amenable reaction conditions. In this context, one reaction that is particularly important from the industrial point of view is cyclohexane aerobic oxidation to a mixture of the corresponding cyclohexanone and cyclohexanol. This industrial oxidation is key for the production of Nylon 6 and Nylon 6,6, two polyamides of growing production. The industrial process is clearly unsatisfactory since it is run at low cyclohexane conversions to avoid the formation of complex mixtures, difficult to isolate. The present review shows the progress made in the use of metal‐organic frameworks as solid catalysts for this important reaction, with emphasis in the intrinsic activity of metal nodes, tuning of the polarity of the internal voids or incorporation of active metal nanoparticles. It is shown that using MOFs as catalysts, it is possible to reach high cyclohexane conversions, while the combined alcohol+ketone selectivity still close to the 90 % limit.
Light can boost ozone efficiency in advanced oxidation processes (AOPs), either by direct ozone photolysis with UV light or by using a photocatalyst that can be excited with UV-Vis or solar light. The present review summarizes literature data on the combination of ozone and the g-C3N4 photocatalyst for the degradation of probe molecules in water, including oxalic, p-hydroxybenzoic and oxamic acids as well as ciprofloxacin and parabens. g-C3N4 is a metal-free visible-light photocatalyst based on abundant elements that establishes a synergistic effect with ozone, the efficiency of the combination of the photocatalysis and ozonation being higher than the sum of the two treatments independently. Available data indicate that this synergy derives from the higher efficiency in the generation of hydroxyl radicals due to the efficient electron quenching by O3 of photogenerated conduction band electrons in the g-C3N4 photocatalyst. Given the wide use of ozonizers in water treatment, it is proposed that their implementation with g-C3N4 photocatalysis could also boost ozone efficiency in the AOPs of real waste waters.
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