Investigating catalytic reaction mechanisms could help guide the design of catalysts. Here, aimed at improving both the catalytic performance and SO 2 resistance ability of catalysts in the selective reduction of NO by NH 3 (NH 3 − SCR), an innovative CeO 2 −SiO 2 mixed oxide catalyst (CeSi2) was developed based on our understanding of both the sulfur poisoning and reaction mechanisms, which exhibited excellent SO 2 /H 2 O resistance ability even in the harsh working conditions (containing 500 ppm of SO 2 and 5% H 2 O). The strong interaction between Ce and Si (Ce−O−Si) and the abundant surface hydroxyl groups on CeSi2 not only provided fruitful surface acid sites but also significantly inhibited SO 2 adsorption. The NH 3 −SCR performance of CeSi2 was promoted by an enhanced Eley−Rideal (E−R) mechanism in which more active acid sites were preserved under the reaction conditions and gaseous NO could directly react with adsorbed NH 3 . This mechanism-enhanced process was even further promoted on sulfated CeSi2.

Para-, or 4-nitrophenol, and related nitroaromatics are broadly used compounds in industrial processes and as a result are among the most common anthropogenic pollutants in aqueous industrial effluent; this requires development of practical remediation strategies. Their catalytic reduction to the less toxic and synthetically desirable aminophenols is one strategy. However, to date, the majority of work focuses on catalysts based on precisely tailored, and often noble metal-based nanoparticles. The cost of such systems hampers practical, larger scale application. We report a facile route to bulk cobalt oxide-based materials, via a combined mechanochemical and calcination approach. Vibratory ball milling of CoCl2(H2O)6 with KOH, and subsequent calcination afforded three cobalt oxide-based materials with different combinations of CoO(OH), Co(OH)2, and Co3O4 with different crystallite domains/sizes and surface areas; Co@100, Co@350 and Co@600 (Co@###; # = calcination temp). All three prove active for the catalytic reduction of 4-nitrophenol and related aminonitrophenols. In the case of 4-nitrophenol, Co@350 proved to be the most active catalyst, therein its retention of activity over prolonged exposure to air, moisture, and reducing environments, and applicability in flow processes is demonstrated.

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The development and implementation of transition-metal-based precatalysts have played crucial roles in modern organic synthesis. However, while the use of such species greatly improves sustainability, their preparative routes often rely on multiple time-, energy-, and solvent-intensive steps. By leveraging solvent-free mechanochemical synthesis through vibratory ball milling, we report the one-pot, one-step synthesis of a range of first-row transition-metal bis­(imino)­pyridine complexes, where both the ligand and coordination complex are assembled in situ. Bis­(imino)­pyridine complexes of the first-row transition metals have an extensive history of application as precatalysts for numerous bond-forming transformations. The method reported herein facilitates access to such species in a time-, solvent-, and space-saving manner which can easily be adapted to any laboratory setting regardless of prior experience with coordination complex synthesis.

“MoCl3(dme)” (dme = 1,2-dimethoxyethane) is an important precursor for midvalent molybdenum chemistry, particularly for triply Mo–Mo bonded compounds of the type Mo2X6 (X = bulky anionic ligand). However, its exact structural identity has been obscure for more than 50 years. In search of a convenient, large-scale synthesis, we have found that trans-MoCl4(Et2O)2 dissolved in dme can be cleanly reduced with dimethylphenylsilane, Me2PhSiH, to provide khaki Mo2Cl6(dme)2 in ∼90% yield. If the reduction is performed on a small scale, single crystals suitable for X-ray crystallography can be obtained. Two different crystal morphologies were identified, each belonging to the P21/n space group, but with slightly different unit cell constants. The refined structure of each form is an edge-shared bioctahedron with overall Ci symmetry and metal–metal separations on the order of 2.8 Å. The bulk material is diamagnetic as determined by both the Gouy method and SQUID magnetometry. Density functional theory calculations suggest a σ2π2δ*2 ground state for the dimer with the diamagnetism arising from a singlet diradical “broken symmetry” electronic configuration. In addition to a definitive structural assignment for “MoCl3(dme)”, this work highlights the utility of organosilanes as easy to handle, alternative reductants for inorganic synthesis.