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Tailoring the CO2adsorption performance of high-aluminum-containing zeolites is typically considered from the perspective of controlling the type and location of extra-framework cations. In this work, using solid-state 29Si nuclear magnetic resonance (NMR), we show that local order, i.e., the aluminum distribution within the framework of Na,Cs-RHO type zeolites with different Al contents, plays a fundamental role in governing the CO2adsorption capacity and structural flexibility. From this analysis, the cation type and location within the RHO structure as a consequence of the framework Al distribution are not the only parameters that deserve consideration. This is despite their paramount importance in optimizing the adsorption capacity of samples with a fixed Al content. In addition, we observe strong correlations between the 29Si NMR barycenter and ellipticity of the eight-ring pore apertures and the nearest neighbor and next-nearest neighbor framework atom distances. From this analysis, we rationalize that the zeolite framework flexibility can be viewed as a consequence of the distribution of Si species rather than being exclusively a consequence of the type of cation loading only.

Projections of climate change impacts on marine ecosystems have revealed long-term declines in global marine animal biomass and unevenly distributed impacts on fisheries. Here we apply an enhanced suite of global marine ecosystem models from the Fisheries and Marine Ecosystem Model Intercomparison Project (Fish-MIP), forced by new-generation Earth system model outputs from Phase 6 of the Coupled Model Intercomparison Project (CMIP6), to provide insights into how projected climate change will affect future ocean ecosystems. Compared with the previous generation CMIP5-forced Fish-MIP ensemble, the new ensemble ecosystem simulations show a greater decline in mean global ocean animal biomass under both strong-mitigation and high-emissions scenarios due to elevated warming, despite greater uncertainty in net primary production in the high-emissions scenario. Regional shifts in the direction of biomass changes highlight the continued and urgent need to reduce uncertainty in the projected responses of marine ecosystems to climate change to help support adaptation planning.

This study presents the influence of polymorphism on the magnetic properties of Co5TeO8. This compound with a spinel-like structure [Co2]A[Co3Te]BO8was synthesized into two polymorphs: one disordered within a cubic Fd3̅mstructure, where Co2+and Te6+ions are randomly distributed on the octahedral B sites [the disordered polymorph can also be presented as an inverse spinel of the formula Co(Co1.5Te0.5)O4] and the other ordered with a cubic P4332 structure where Co2+and Te6+ions are ordered on the B sites. The macroscopic magnetic measurements showed that both polymorphs present a ferrimagnetic ordering, below ∼40 K, and a second transition is also observed at 27 K for the ordered polymorph. Neutron powder diffraction data between room temperature and 1.7 K showed as well the presence of short-range magnetic ordered clusters, which appears for both polymorphs below 200 K. At lower temperature, these short-range orders are transformed into long-range ferrimagnetic orders. Below TC= 40 K, the colinear ferrimagnetic structure of the disordered polymorph is described with the I41/am′d′ space group. The ordered polymorph undergoes an incommensurate ferrimagnetic spiral spin ordering below TC1= 45 K, followed by a second magnetic phase transition at TC2= 27 K. This last transition is associated with the emergence of an additional ferrimagnetic component and an abrupt change in the magnitude of the magnetic propagation vector k= [0, 0, γ] from γ = 0.086 at T= 30 K to γ ≈ 0.14 in the range between 27 and 1.7 K. The magnetic symmetry of the ordered polymorph is described with the P43(00γ)0 magnetic superspace group. We evidenced that the ordering of Co2+/Te6+on the B sites changes all of the Co–Co and Co–O distances and thus all JAB, JAA, and JBBexchange interactions, between the A and B sites, which are able to stabilize the incommensurate spin modulation in the ordered polymorph.

Inverse trirutile Mn2TeO6was investigated using in situ neutron and X-ray powder diffraction between 700 °C and room temperature. When the temperature was decreased, a structural phase transition was observed around 400 °C, from a tetragonal (P42/mnm) to a monoclinic phase (P21/c), involving a doubling of the cell parameter along b. This complex monoclinic structure has been solved by combining electron, neutron, and synchrotron powder diffraction techniques at room temperature. It can be described as a distorted superstructure of the inverse trirutile structure, in which compressed and elongated MnO6octahedra alternate with more regular TeO6octahedra, forming a herringbone-like pattern. Rietveld refinements, carried out with symmetry-adapted modes, show that the structural transition, arguably of Jahn–Teller origin, is driven by a single primary mode.

Flexible small-pore zeolites are interesting candidates for flue and natural gas processing due to their high sorption capacity and selectivity. It is generally accepted that their high CO2/CH4selectivity is due to cation gating behavior such as the “trapdoor” effect or cation-controlled molecular sieving. Herein, nanosized RHO-type zeolite containing only inorganic cations (Na+and Cs+) has been prepared from a colloidal precursor suspension at 90 °C for 1 h without the use of expensive organic structure directing agents. The high Cs content significantly improved the thermal stability of the RHO nanocrystals up to 550 °C. The flexibility of the RHO cages upon water adsorption/desorption is demonstrated. The dehydration of the nanosized RHO zeolite resulted in two dehydrated RHO phases, the first one presents an enlargement of the cubic unit cell and a transformation from distorted to the more regular d8runits, and the second one presents a reduction of the cubic unit cell and an increase of the distortion of the d8runits. The 8-rings elliptical distortions of the as-synthesized RHO (hydrated form) of 1.87 Å changed to 0.94 and 2.16 Å for the two dehydrated RHO forms. The flexibility of the nanosized RHO zeolite is due to the ability of the Cs+cation to displace out from and into the D8R window sites which is of great importance for controlling the selective adsorption capacity of the RHO zeolite. The flexible RHO-type nanosized zeolite exhibited great selectivity toward CO2over CH4. The adsorption capacity is retained after 10 cycles of CO2adsorption/desorption and the crystalline structure is fully preserved.

Direct evidence of the successful incorporation of atomically dispersed molybdenum (Mo) atoms into the framework of nanosized MFI zeolite is demonstrated for the first time. Homogeneous distribution of Mo with a size of 0.05 nm is observed by scanning transmission electron microscopy high-angle annular dark-field imaging (STEM-HAADF). 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) and Fourier-transform infrared (FT-IR) spectroscopy, using trimethylphosphine oxide (TMPO) and deuterated acetonitrile as probe molecules, reveal a homogeneous distribution of Mo in the framework of MFI nanozeolite, and the presence of Lewis acidity. 31P MAS NMR using TMPO shows probe molecules interacting with isolated Mo atoms in the framework, and physisorbed probe molecules in the zeolite channels. Moreover, 2D 31P–31P MAS radio frequency-driven recoupling NMR indicates the presence of one type of Mo species in different crystallographic positions in the MFI framework. The substitution of framework Si by Mo significantly reduces the silanol defect content, making the resulting zeolite highly hydrophobic. In addition, the insertion of Mo into the MFI structure induces a symmetry lowering, from orthorhombic (Pnma), typical of high silica MFI, to monoclinic (P21/n), as well as an expansion of unit cell volume. The novel material opens many opportunities of catalysts design for application in mature and emerging fields.

The host–guest and guest–guest interactions governing the CO2adsorption/desorption in two nanosized zeolite samples with FAU framework type and different Si/Al ratios (Na–X Si/Al = 1.24 and Na–Y Si/Al = 2.54) and cation distribution were investigated by in situ synchrotron high-resolution X-ray powder diffraction (XRPD) and in situ Fourier transform infrared (FTIR) spectroscopy. The two complementary techniques allow probing the CO2adsorption/desorption in the FAU zeolites at different levels, that is, average structure by XRPD versus local structure by FTIR spectroscopy . The presence of physisorbed CO2molecules in both zeolites was detected by XRPD, whereas only a high amount of chemisorbed CO2in the Na–X zeolite was found. The presence of unshielded Na cations and H2O molecules in the supercage of the Na–X sample induces the formation of stable bidentate bicarbonate groups. Evacuating CO2-loaded samples resulted in the efficient removal of physisorbed CO2from both nanosized zeolites; on the contrary, high temperature is required to remove the chemisorbed species from the nanosized Na–X zeolite. Understanding the CO2sorption behavior and capacity of nanosized zeolites is of great importance in broadening their use in environmental, clinical, and biomedical applications.

Sub-nanometer silver clusters that exhibit discrete electronic structure with molecular-like properties are highly desirable in various technologies. However, the methods for their preparation suffer from limitations related with the reproducibility and particles uniformity and/or the possibility of the scale-up. Another critical drawback is that free sub-nanometer silver clusters tend to aggregate into larger particles. In this work, a new approach that successfully overcomes the above limitations is developed. It allows, for the first time, an ultrafast preparation of sub-nanometer silver particles with high abundance, uniformity (7 Å), and stability into the cages of nanosized zeolite crystals. The new method consists of UV excitation of a water suspension of nanozeolite containing photoactive vanadate clusters in the presence of ethanol (as an electron donor) and silver precursor. The characteristic features of sub-nanometer silver particles are presented, and the mechanism of their formation is discussed. Sub-nanometer Ag clusters exhibit exceptional photocatalytic activity and selectivity in the reforming of formic acid to H2and CO2under visible light.

We report the possibility of extending the so-called stairlike Aurivilius phases in the pseudobinary Bi5Nb3O15–ABi2Nb2O9(A = Ba and Sr) over a wide range of compositions. These phases are characterized by a discontinuous stacking of [Bi2O2] slabs and perovskite blocks, leading to long-period intergrowths stabilized as a single phase. When analyses from precession electron diffraction tomography and X-ray and neutron powder diffraction are combined, the monoclinic incommensurately modulated structure with q= αa* + γc* previously proposed for the ABi7Nb5O24composition could be generalized to the Bi5Nb3O15–ABi2Nb2O9(A = Ba and Sr) compounds. Considering the compositions expressed as (A,Bi)1–xNbxO3–3x, the stacking sequence associated with compositions ranging from x= 2/5to 3/8is governed by the component γ of the modulation vector and can be predicted following a Farey tree hierarchy independently to the A cation. The length of the steps, characteristic of the stairlike nature, is controlled by the α component and depends on the substitution ratio A/Bi and the nature of A (A = Ba and Sr). This study highlights the compositional flexibility of stairlike Aurivillius phases.

New ferroelectric layered materials were found in the pseudobinary system Bi5Nb3O15–ABi2Nb2O9(A= Ba, Sr and Pb). Preliminary observations made by transmission electron microscopy indicate that these compounds exhibit a complex incommensurately modulated structure. A (3 + 1)D structural model is obtained using ab initio phasing by charge flipping based on the analysis of precession electron diffraction tomography data. The (3 + 1)D structure is further validated by a refinement against neutron powder diffraction. These materials possess a layered structure with discontinuous [Bi2O2] slabs and perovskite blocks. While these structural units are characteristics of Aurivillius phases, the existence of periodic crystallographic shear planes offers strong similarities with collapsed or stairlike structures known in high-Tc superconductors and related compounds. Using dielectric spectroscopy, we study the phase transitions of these new layered materials. For A = Ba and Sr, a Vögel–Fulcher-like behavior characteristic of the so-called relaxor ferroelectrics is observed and compared to “canonical” relaxors. For A = Sr, the absence of a Burns temperature separated from the freezing temperature appears as a rather unusual behavior.

Sr4Mn2Cu5O4S5 contains manganese oxide sheets separated by unusual antifluorite-type Cu3S3 layers in which copper(i) ions are distributed over three- and four-coordinate sites in a similar fashion to in α-Cu2−xS and suggestive of high two-dimensional copper ion mobility.

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