RESUMEN
Emissions of nitrogen oxide (NOx) species (NO and NO2) and nitrate/nitrite NOx-, such as NO3- and NO2-, have led to serious water pollution and climate challenges. How to remove these wastes is a global problem that urgently needs to be addressed. As reported, electrochemical catalytic technology under ambient conditions is of great interest for NOx/NOx- removal. Additionally, the in situ utilization of surface-adsorbed nucleophilic intermediates generated from the electrochemical reduction of NOx/NOx- can provide a sustainable strategy for building C-N bonds, upgrading waste NOx/NOx- into value-added organic products, such as amines, oximes, amides, and amino acids, while remediating the environment. This review summarizes the most recent progress in the construction of nitrogen compounds by coupling electrochemical NOx/NOx- reduction reactions with inorganic/organic substrates, focuses on understanding the adsorption-transformation mechanism during the NOx/NOx- reduction process, and discusses multiple side reactions and complex pathways. Important strategies, such as coupled system development and catalyst preparation, are also presented to broaden the range of nitrogen compounds and improve yields. Finally, a few key challenges and future research directions for the development of efficient and low-cost electrochemical C-N coupling processes are discussed.
RESUMEN
The industrial production of nylon 6 usually includes synthesizing caprolactam through the cyclohexanone-hydroxylamine route. This approach requires complex protocols, elevated temperatures, noble metal catalysts and the use of hazardous strong acids or hydroxylamine. Additionally, a significant quantity of ammonium sulphate is generated during the synthesis procedure. This study aims to develop an electrochemical reduction system for the conversion of ADN generated from the electrolytic dimerization of acrylonitrile (AN) to 6-aminocapronitrile (ACN), a precursor of nylon 6. This system utilizes a cost-effective Cu nanomaterial under eco-friendly conditions, avoiding lengthy and harsh processes, eliminating NH2OH use, and reducing low-value ammonium sulfate generation. This electrosynthesis method maintains approximately 85% ACN selectivity at 40-100 mA cm-2 when passing the charge required for 37% theoretical conversion. When extending the reaction time to achieve an 80% conversion, ACN selectivity still reached 81.6%, exceeding the theoretical value of non-selective hydrogenation by 20%. The pseudo-first-order reaction kinetic modeling proves that the reaction rate constant for ADN hydrogenation is significantly greater than that for ACN hydrogenation, highlighting the selectivity advantage of the system for ACN. This study establishes the foundation for developing a continuous electrolysis process to produce the nylon 6 precursor from AN feedstock.
RESUMEN
Substituting the low-value oxygen evolution reaction (OER) with thermodynamically more favored organic oxidation such as furfural oxidation reaction (FOR) is regarded as a perspective approach to decrease energy cost of hydrogen evolution from water splitting. However, the kinetic of FOR can be even more sluggish than OER under large current density. In this work, a strategy is proposed to accelerate FOR by enhancing the adsorption of oxygenates on active sites. Over the prepared NiMoP/NF anode, only 1.46 V versus RHE is required in furfural solution to achieve 500 mA cm-2 , significantly better than the OER activity over commercial RuO2 /NF under the same current density (1.57 V vs RHE).
RESUMEN
A core-shell TS-1@Co-N-C was prepared by thermally pyrolyzing polydopamine and cobalt acetate outside TS-1 crystals. The Co-N-C shell catalyzes the electrochemical oxygen reduction to hydrogen peroxide (H2O2), while the TS-1 core catalyzes the oxidation of organic reagents. It achieved a H2O2 selectivity higher than 95% without organics, and accomplished an excellent bisphenol selectivity of 99.45% when coupled with phenol oxidation. Moreover, paired oxidation of furfural at both cathodic and anodic sides further led to an overall Faradaic efficiency of 141.09%. This bifunctional catalyst helps to integrate the in situ generation and usage of H2O2 into a single electrode, thus reduces the equipment and operating costs.
RESUMEN
A ruthenium carbene catalyst chelated with a 3,4-dioxocyclobut-1-ene-1,2-dithiolate ligand was synthesized and its molecular structure was determined by single-crystal X-ray diffraction. The Ru catalyst had excellent catalytic activity with high yields and good Z/E ratios for the ring opening metathesis polymerization (ROMP) of norbornene (yield: 96%/Z/E: 86 : 14) and 1,5-cyclooctadiene (yield: 86%/Z/E: 91 : 9) and for ring opening cross metathesis (ROCM) reactions of norbornene/5-norbornene-2-exo, 3-exo-dimethanol with styrene (yields: 64%-92%/Z/E: 97 : 3-98 : 2) or 4-fluorostyrene (yield: 46%-94%/Z/E: 98 : 2). The catalyst also had high Z-stereoretentivity (91 : 9-98 : 2) for cross-metathesis (CM) reactions of terminal olefins with (Z)-2-butene-1,4-diol. More importantly, the catalyst had moderate Z-stereoselectivity for homometathesis reactions of terminal olefins giving cis-olefins as the major products (Z/E ratios of 70 : 30-77 : 23). Like other Ru carbene complexes, the catalyst tolerates many different functional groups. The presented data, supported by DFT calculations, show that our catalyst, bearing a chelating 3,4-dioxocyclobut-1-ene-1,2-dithiolate ligand, exhibits higher stability towards air than Hoveyda's stereoretentive complex systems.
RESUMEN
A ruthenium carbene catalyst containing a 1,2-dicarbadodecaborane(12)-1,2-dithiolate ligand was synthesized, and the structure was determined by single crystal X-ray diffraction. This new ruthenium carbene catalyst can catalyze the ring opening metathesis polymerization (ROMP) reaction of norbornene to give the corresponding Z-polymer (Z/E ratio, 98 : 2) in high yield (93%); ring opening cross metathesis (ROCM) reactions of norbornene/5-norbornene-2-exo, 3-exo-dimethanol with styrene or 4-fluorostyrene to give the corresponding Z-olefin products (Z/E ratios, 97 : 3-98 : 2), respectively, in high yields (73%-88%); cross metathesis (CM) reactions of terminal alkenes with (Z)-but-2-ene-1,4-diol to give high Z-olefin products in low yields; homometathesis reactions of terminal alkenes to give olefin products in low yields. Like other ruthenium carbene catalysts, the new complex tolerates many different functional groups. DFT calculations were also performed in order to understand the process of forming Z-olefin products and the decomposition process of catalysts.
RESUMEN
An indolinooxazolidine tagged N-heterocyclic carbene Ru olefin metathesis catalyst was synthesized and the molecular structure of this new Ru complex was determined by single crystal X-ray diffraction. This complex is a homogeneous catalyst and can be recovered by controlling the polarity of the indolinooxazolidine tag. Under acidic conditions the indolinooxazolidine tag exists as an open protonated form and under basic conditions the tag is in a closed form. The distribution of this catalyst in a two-phase system can be controlled by simply changing the pH, making the recovery of this catalyst easily obtainable.
