Nitrogen dioxide (NO) is a major air pollutant causing significant environmental and health problems. We report reversible adsorption of NO in a robust metal-organic framework. Under ambient conditions, MFM-300(Al) exhibits a reversible NO isotherm uptake of 14.1 mmol g, and, more importantly, exceptional selective removal of low-concentration NO (5,000 to <1 ppm) from gas mixtures. Complementary experiments reveal five types of supramolecular interaction that cooperatively bind both NO and NO molecules within MFM-300(Al). We find that the in situ equilibrium 2NO ↔ NO within the pores is pressure-independent, whereas ex situ this equilibrium is an exemplary pressure-dependent first-order process. The coexistence of helical monomer-dimer chains of NO in MFM-300(Al) could provide a foundation for the fundamental understanding of the chemical properties of guest molecules within porous hosts. This work may pave the way for the development of future capture and conversion technologies.

Bandgap engineering of zinc oxide semiconductors can be achieved using a bio-inspired method. During a bioInspired crystallization process, incorporation of amino acids into the crystal structure of ZnO induces lattice strain that leads to linear bandgap shifts. This allows for fine tuning of the bandgap in a bio-inspired route.

Crystallite size effects can influence the performance of battery materials by making the structural chemistry deviate from what is predicted by the equilibrium phase diagram. The implications of this are profound: the properties of many battery materials should be reassessed. Sodium ion battery anodes made from nanocrystalline bismuth form different phases during electrochemical cycling compared to anodes with larger crystallites. This is due to the formation of a metastable cubic polymorph of Na 3 Bi on the crystallite surfaces. The structural differences (weaker Na−Bi bonds, different coordination of Na to Bi) between the metastable cubic Na 3 Bi phase found in the nanocrystals and the hexagonal equilibrium polymorph which dominates the larger crystallites offer an explanation for the improvements in cycling behavior observed for the nanostructured anode.

International audienceThe electrochemical properties of the O3-type NaxMn1/3Fe2/3O2 (x = 0.77) phase used as positive electrode material in Na batteries were investigated in the 1.5–3.8 V, 1.5–4.0 V and 1.5–4.3 V ranges. We show that cycling the Na cells in a wider voltage range do not induce a significant gain on long term cycling as the discharge capacities reached for the three experiments are identical after the 14th cycle. The structural changes the material undergoes from 1.5 V (fully intercalated state) to 4.3 V were investigated by operando in situ X-ray powder diffraction (XRPD) and were further characterized by ex situ synchrotron XRPD. We show that the low amount of Mn3+ ions (≈33% of total Mn+ ions) is enough to induce a cooperative Jahn–Teller effect for all MO6 octahedra in the fully intercalated state. Upon deintercalation the material exhibits several structural transitions: O′3 → O3 → P3. Furthermore, several residual phases are observed during the experiment. In particular, a small part of the O3 type is not transformed to P3 but is always involved in the electrochemical process. To explain this behaviour the hypothesis of an inhomogeneity, which is not detected by XRD, is suggested. All phases converge into a poorly crystallized phase for x ≈ 0.15. The short interslab distance of the resulting phase strongly suggests an octahedral environment for the Na+ ions. X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy were used to confirm the activity of the Mn4+/Mn3+ and Fe4+/Fe3+ redox couples in the low and high voltage regions, respectively. 57Fe Mössbauer spectroscopy also showed an increase of the disorder into the material upon deintercalation

Sodium-ion batteries may become an inexpensive alternative to lithium-ion batteries for large-scale stationary storage of energy generated by intermittent renewable sources. The key for the deployment of this technology is the development of suitable anode materials which can rival the graphite anodes used in lithium-ion batteries in terms of energy density, cycle life, rate performance, and safety. Here, we demonstrate that the bismuth metalates, BiVO4 and Bi2(MoO4)3, as representatives of ternary metalates, can cope with these requirements. High specific capacities (367 mAh/g and 352 mAh/g, respectively), exceptionally high cycling stability for alloying anodes (up to 79% of the first charge capacity is retained over 1000 cycles at ∼1C for Bi2(MoO4)3), better high-rate performance compared to other Bi-based anodes, low environmental load (Bi has low toxicity for a heavy metal), and low manufacturing costs (e.g., BiVO4 is a commercial yellow pigment) make this novel class of anode materials suitable for large-scale electrical energy storage applications. Operando XANES, ex situ XRD, and DFT analysis suggest that the initial compounds are converted into alloying Bi nanocrystallites confined in a matrix of electrochemically active insertion hosts Na3+x VO4 and Na2+x MoO4, respectively. The Bi metalate phases are not reformed on charge, and on subsequent cycles the reaction with Bi metal and vanadate/molybdate phases gives rise to the reversible capacity. The nanostructured composite anode thus obtained has excellent high rate performance and retains its capacity over hundreds of cycles.