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1. Nickel-mediated N–N bond formation and N ₂ O liberation via nitrogen oxyanion reduction

   https://doi.org/10.1039/D1SC02846D  

   Beagan, Daniel M.; Cabelof, Alyssa C.; Pink, Maren; Carta, Veronica; Gao, Xinfeng; Caulton, Kenneth G. (August 2021, Chemical Science)

   The syntheses of (DIM)Ni(NO 3 ) 2 and (DIM)Ni(NO 2 ) 2 , where DIM is a 1,4-diazadiene bidentate donor, are reported to enable testing of bis boryl reduced N-heterocycles for their ability to carry out stepwise deoxygenation of coordinated nitrate and nitrite, forming O(Bpin) 2 . Single deoxygenation of (DIM)Ni(NO 2 ) 2 yields the tetrahedral complex (DIM)Ni(NO)(ONO), with a linear nitrosyl and κ 1 -ONO. Further deoxygenation of (DIM)Ni(NO)(ONO) results in the formation of dimeric [(DIM)Ni(NO)] 2 , where the dimer is linked through a Ni–Ni bond. The lost reduced nitrogen byproduct is shown to be N 2 O, indicating N–N bond formation in the course of the reaction. Isotopic labelling studies establish that the N–N bond of N 2 O is formed in a bimetallic Ni 2 intermediate and that the two nitrogen atoms of (DIM)Ni(NO)(ONO) become symmetry equivalent prior to N–N bond formation. The [(DIM)Ni(NO)] 2 dimer is susceptible to oxidation by AgX (X = NO 3 − , NO 2 − , and OTf − ) as well as nitric oxide, the latter of which undergoes nitric oxide disproportionation to yield N 2 O and (DIM)Ni(NO)(ONO). We show that the first step in the deoxygenation of (DIM)Ni(NO)(ONO) to liberate N 2 O is outer sphere electron transfer, providing insight into the organic reductants employed for deoxygenation. Lastly, we show that at elevated temperatures, deoxygenation is accompanied by loss of DIM to form either pyrazine or bipyridine bridged polymers, with retention of a BpinO − bridging ligand. 

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2. Anomalous thermal transport behavior in graphene-like carbon nitride (C ₃ N)

   https://doi.org/10.1039/d2tc02425j  

   Qin, Guangzhao; Lin, Jianzhou; Wang, Huimin; Hu, Jianjun; Qin, Zhenzhen; Hu, Ming (August 2022, Journal of Materials Chemistry C)

   The success of graphene created a new era in materials science, especially for two-dimensional (2D) materials. 2D single-crystal carbon nitride (C 3 N) is the first and only crystalline, hole-free, single-layer carbon nitride and its controlled large-scale synthesis has recently attracted tremendous interest in thermal transport. Here, we performed a comparative study of thermal transport between monolayer C 3 N and the parent graphene, and focused on the effect of temperature and strain on the thermal conductivity ( κ ) of C 3 N, by solving the phonon Boltzmann transport equation (BTE) based on first-principles calculations. The κ of C 3 N shows an anomalous temperature dependence, and the κ of C 3 N at high temperatures is larger than the expected value following the common trend of κ ∼ 1/ T . Moreover, the κ of C 3 N is found to be increased by applying a bilateral tensile strain, despite its similar planar honeycomb structure to graphene. The underlying mechanism is revealed by providing direct evidence for the interaction between lone-pair N-s electrons and bonding electrons from C atoms in C 3 N based on the analysis of orbital-projected electronic structures and electron localization function (ELF). Our research not only conduct a comprehensive study on the thermal transport in graphene-like C 3 N, but also reveal the physical origin of its anomalous properties, which would have significant implications on the future studies of nanoscale thermal transport. 

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3. Synthesis of α′′-Fe ₁₆ N ₂ ribbons with a porous structure

   https://doi.org/10.1039/c9na00008a  

   Liu, Jinming; Guo, Guannan; Zhang, Fan; Wu, Yiming; Ma, Bin; Wang, Jian-Ping (April 2019, Nanoscale Advances)

   The microstructure of FeCuB ribbons (∼20 μm thick) was modified to fabricate α′′-Fe 16 N 2 at a temperature as low as 160 °C. The ribbon samples were heat treated first at a temperature reaching 930 °C and then quenched down to room temperature. During the heat treatment, ribbon samples were oxidized, and hydrogen reduction was then conducted to remove the oxygen from the ribbon samples. The reduced ribbon samples had a porous structure, which improved the nitrogen diffusion efficiency and decreased the fabrication temperature of α′′-Fe 16 N 2 down to 160 °C. It was demonstrated that the techniques for microstructure control in this method including oxidation and reduction helped obtain the α′′-Fe 16 N 2 phase with high coercivity, thus manifesting this could be a promising technique for low-temperature nitridation on ribbons in general. 

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4. Synthesis and Li-ion electrode properties of layered MAB phases Ni _n+1 ZnB _n ( n = 1, 2)

   https://doi.org/10.1039/c9ta12937e  

   Rezaie, Amir A.; Yan, Zheng; Scheifers, Jan P.; Zhang, Jian; Guo, Juchen; Fokwa, Boniface P. (January 2020, Journal of Materials Chemistry A)

   null (Ed.)

   Ternary MAB phases (layered transition metal borides) have recently attracted interest due to their exfoliation potential toward MBenes (analogous to MXenes), which are predicted to have excellent Li-ion battery performance. We have achieved single-phase synthesis of two MAB phases with general composition Ni n+1 ZnB n ( n = 1, 2), the crystal structures of which contain zinc layers sandwiched between thin ( n = 1) and thick ( n = 2) Ni–B slabs. Highly stacked MAB sheets were confirmed by X-ray diffraction and high-resolution scanning electron microscopy for both materials. Exposing Ni n+1 ZnB n to diluted hydrochloric acid led to the creation of crystalline microporous structures for n = 1 and non-porous detached sheets for n = 2. Both morphologies transformed the inactive bulk materials into highly active Li-ion battery anodes with capacities of ∼90 mA h g −1 ( n = 1) and ∼70 mA h g −1 ( n = 2) at a 100 mA g −1 lithiation–delithiation rate. The XPS analysis and BET surface area measurements reveal that the increased surface area and the reversible redox reaction of oxidized nickel species are responsible for this drastic increase of the lithiation–delithiation capacity. This proof of concept opens new avenues for the development of porous MAB, MAB nanosheets, MBenes and their composites for metal-ion battery applications. 

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5. A practical way to enhance the synthesis of N ₈ ⁻ from an N ₃ ⁻ precursor, studied by both computational and experimental methods

   https://doi.org/10.1039/D0CP06053D  

   Alzaim, Safa; Wu, Zhiyi; Benchafia, El Mostafa; Young, Joshua; Wang, Xianqin (July 2021, Physical Chemistry Chemical Physics)

   null (Ed.)

   Polymeric nitrogen (PN) belongs to a general family of materials containing all-nitrogen molecules or clusters. Although it is rare and challenging to synthesize PN members, they are attracting increasing scientific attention due to their high energy storage capacity and possible use as a green catalyst. A few theoretical calculations predicted the possible PN phases from N 2 gas, but they all require extremely high pressures and temperatures to synthesize. In this work, a practical way to synthesize N 8 polymeric nitrogen from an N 3 − precursor is elucidated using density functional theory calculations. The detailed mechanism, , is determined. The calculated energy barriers indicate that the first step is the rate-limiting step. This result guides us to rationally synthesize N 8 under UV (254 nm) irradiation, chosen based on the calculated absorption spectrum for the azide anion. As expected, UV irradiation enhances N 8 yields by nearly four times. This provides an interesting route to the scalable synthesis of high energy density N 8 compounds. 

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