The cleavage and functionalization of recalcitrant carbon─carbon bonds is highly challenging but represents a very powerful tool for value-added transformation of feedstock chemicals. Here, an enzyme-mimic iron single-atom catalyst (SAC) bearing iron (III) nitride (FeN 3 ) motifs was prepared and found to be robust for cleavage and cyanation of carbon–carbon bonds in secondary alcohols and ketones. High nitrile yields are obtained with a wide variety of functional groups. The prepared FeN 3 -SAC exhibits high enzyme-like activity and is capable of generating a dioxygen-to-superoxide radical at room temperature, while the commonly reported FeN 4 -SAC bearing FeN 4 motifs was inactive. Density functional theory (DFT) calculation reveals that the activation energy of dioxygen activation and the activation energy of the rate-determining step of nitrile formation are lower over FeN 3 -SAC than FeN 4 -SAC. In addition, DFT calculation also explains the catalyst’s high selectivity for nitriles.

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Catalytic ammoxidation of alcohols into nitriles is an essential reaction in organic synthesis. While highly desirable, conducting the synthesis at room temperature is challenging, using NH 3 as the nitrogen source, O 2 as the oxidant, and a catalyst without noble metals. Herein, we report robust photocatalysts consisting of Fe(III)-modified titanium dioxide (Fe/TiO 2 ) for ammoxidation reactions at room temperature utilizing oxygen at atmospheric pressure, NH 3 as the nitrogen source, and NH 4 Br as an additive. To the best of our knowledge, this is the first example of catalytic ammoxidation of alcohols over a photocatalyst using such cheap and benign materials. Various (hetero) aromatic nitriles were synthesized at high yields, and aliphatic alcohols could also be transformed into corresponding nitriles at considerable yields. The modification of TiO 2 with Fe(III) facilitates the formation of active • O 2 − radicals and increases the adsorption of NH 3 and amino intermediates on the catalyst, accelerating the ammoxidation to yield nitriles. The additive NH 4 Br impressively improves the catalytic efficiency via the formation of bromine radicals (Br • ) from Br − , which works synergistically with • O 2 − to capture H • from C α -H, which is present in benzyl alcohol and the intermediate aldimine (RCH�NH), to generate the active carbon-centered radicals. Further, the generation of Br • from the Br − additive consumes the photogenerated holes and OH • radicals to prevent over-oxidation, significantly improving the selectivity toward nitriles. This amalgamation of function and synergy of the Fe(III)-doped TiO 2 and NH 4 Br reveals new opportunities for developing semiconductor-based photocatalytic systems for fine chemical synthesis.

The development of metal-free catalytic systems is highly desirable in organic transformation. Herein, a biomass-derived carbon catalyst with a high surface area was discovered to be robust for the metal-free and additive-free synthesis of cyclic imides and nitriles from ketones via the strategy of oxidative cleavage of C(O)−C bonds for the first time, which remains a kind of challenging organic transformation even for metal catalysts. Experimental data and DFT calculations revealed that both the defective sites and surface oxygenfunctional groups, particularly, the carboxylic acid groups in the carbon catalyst, were important for this transformation in which the defective sites activated O 2 to generate the reactive oxygen species and the oxygen-containing functional groups facilitated the adsorption and activation of ketones on the catalyst surface to improve the catalytic efficiency. A plausible reaction mechanism was proposed for the oxidative transformation of ketones into imides and nitriles over the carbon catalyst.

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