Tailoring the reaction kinetics is the central theme of designer electrocatalysts, which enables the selective conversion of abundant and inert atmospheric species into useful products. Here we show a supporting effect in tuning the electrocatalytic kinetics of oxygen reduction reaction (ORR) from four-electron to two-electron mechanism by docking metalloporphyrin-based metal-organic frameworks (MOFs) crystals on graphene support, leading to highly selective peroxide production with faradaic efficiency as high as 93.4%. A magic angle of 38.1° tilting for the co-facial alignment was uncovered by electron diffraction tomography, which is attributed to the maximization of π-π interaction for mitigating the lattice and symmetry mismatch between MOF and graphene. The facilitated electron migration and oxygen chemisorption could be ascribed to the supportive effect of graphene that disperses of the electron state of the active center, and ultimately regulates rate-determining step.

Chiral mesostructures exhibit distinctive twisting and helical hierarchical stacking ranging from atomic to micrometre scales with fascinating structural-chiral anisotropy properties. However, the detailed determination of their multilevel chirality remains challenging due to the limited information from spectroscopy, diffraction techniques, scanning electron microscopy and the two-dimensional projections in transmission electron microscopy. Herein, we report a general approach to determine chiral hierarchical mesostructures based on three-dimensional electron diffraction tomography (3D EDT), by which the structure can be solved synchronously according to the quantitative measurement of diffraction spot deformations and their arrangement in reciprocal space. This method was verified on two samples-chiral mesostructured nickel molybdate and chiral mesostructured tin dioxide-revealing hierarchical chiral structures that cannot be determined by conventional techniques. This approach provides more precise and comprehensive identification of the hierarchical mesostructures, which is expected to advance our understanding of structural-chiral anisotropy at the fundamental level.

Abstract Chiral mesostructures exhibit distinctive twisting and helical hierarchical stacking ranging from atomic to micrometre scales. A detailed analysis of these materials is key to understanding their characteristic chiral anisotropy. However, the determination of these multilevel chirality remains challenging due to the limited information from spectroscopy, diffraction techniques, scanning electron microscopy and the two-dimensional projections in transmission electron microscopy. Herein, we report a general approach to determine chiral hierarchical mesostructures based on three-dimensional electron diffraction tomography (3D EDT), by which the structure can be solved synchronously according to the quantitative measurement of diffraction spot deformations and their arrangement in reciprocal space. This method was verified on two samples—chiral mesostructured nickel molybdate and chiral mesostructured tin dioxide—revealing hierarchical chiral structures that cannot be determined by conventional techniques. This approach provides more precise and comprehensive identification of the hierarchical mesostructures, which is expected to advance our understanding of structural–chiral anisotropy at the fundamental level.

A Correction to this paper has been published: https://doi.org/10.1038/s41586-020-03101-x

Copper perchlorophthalocyanine (CuPcCl16, CuC32N8Cl16, Pigment Green 7) is one of the commercially most important green pigments. The compound is a nanocrystalline fully insoluble powder. Its crystal structure was first addressed by electron diffraction in 1972 [Uyeda et al. (1972). J. Appl. Phys. 43, 5181–5189]. Despite the commercial importance of the compound, the crystal structure remained undetermined until now. Using a special vacuum sublimation technique, micron-sized crystals could be obtained. Three-dimensional electron diffraction (3D ED) data were collected in two ways: (i) in static geometry using a combined stage-tilt/beam-tilt collection scheme and (ii) in continuous rotation mode. Both types of data allowed the crystal structure to be solved by direct methods. The structure was refined kinematically with anisotropic displacement parameters for all atoms. Due to the pronounced crystal mosaicity, a dynamic refinement was not feasible. The unit-cell parameters were verified by Rietveld refinement from powder X-ray diffraction data. The crystal structure was validated by many-body dispersion density functional theory (DFT) calculations. CuPcCl16 crystallizes in the space group C2/m (Z = 2), with the molecules arranged in layers. The structure agrees with that proposed in 1972.

Correction to this paper has been published: https://doi.org/10.1038/s41586-020-03101-x

Metal–organic frameworks (MOFs) 1 – 3 are known for their specific interactions with gas molecules 4 , 5 ; this, combined with their rich and ordered porosity, makes them promising candidates for the photocatalytic conversion of gas molecules to useful products 6 . However, attempts to use MOFs or MOF-based composites for CO 2 photoreduction 6 – 13 usually result in far lower CO 2 conversion efficiency than that obtained from state-of-the-art solid-state or molecular catalysts 14 – 18 , even when facilitated by sacrificial reagents. Here we create ‘molecular compartments’ inside MOF crystals by growing TiO 2 inside different pores of a chromium terephthalate-based MOF (MIL-101) and its derivatives. This allows for synergy between the light-absorbing/electron-generating TiO 2 units and the catalytic metal clusters in the backbones of MOFs, and therefore facilitates photocatalytic CO 2 reduction, concurrent with production of O 2 . An apparent quantum efficiency for CO 2 photoreduction of 11.3 per cent at a wavelength of 350 nanometres is observed in a composite that consists of 42 per cent TiO 2 in a MIL-101 derivative, namely, 42%-TiO 2 -in-MIL-101-Cr-NO 2 . TiO 2 units in one type of compartment in this composite are estimated to be 44 times more active than those in the other type, underlining the role of precise positioning of TiO 2 in this system.

Triply periodic continuous morphologies (networks) arising as a result of the microphase separation in block copolymer melts have so far never been observed self-assembled in systems of particles with spherically symmetric interaction. We report a molecular dynamics simulation where two simple one-component liquids form upon cooling an equilibrium network with the Fddd space group symmetry. This complexity reduction in the liquid network formation in terms of the particle geometry and the number of components evidences the generic nature of this class of phase transition, suggesting opportunities for producing these structures in a variety of new systems.

Investigation of a chromium-based metal-organic framework shows that the location of added TiO(2)inside specific mesopores strongly affects the ability of the material to catalyse photoreduction of CO2. Metal-organic frameworks (MOFs)(1-3)are known for their specific interactions with gas molecules(4,5); this, combined with their rich and ordered porosity, makes them promising candidates for the photocatalytic conversion of gas molecules to useful products(6). However, attempts to use MOFs or MOF-based composites for CO(2)photoreduction(6-13)usually result in far lower CO(2)conversion efficiency than that obtained from state-of-the-art solid-state or molecular catalysts(14-18), even when facilitated by sacrificial reagents. Here we create 'molecular compartments' inside MOF crystals by growing TiO(2)inside different pores of a chromium terephthalate-based MOF (MIL-101) and its derivatives. This allows for synergy between the light-absorbing/electron-generating TiO(2)units and the catalytic metal clusters in the backbones of MOFs, and therefore facilitates photocatalytic CO(2)reduction, concurrent with production of O-2. An apparent quantum efficiency for CO(2)photoreduction of 11.3 per cent at a wavelength of 350 nanometres is observed in a composite that consists of 42 per cent TiO(2)in a MIL-101 derivative, namely, 42%-TiO2-in-MIL-101-Cr-NO2. TiO(2)units in one type of compartment in this composite are estimated to be 44 times more active than those in the other type, underlining the role of precise positioning of TiO(2)in this system.

Triply periodic continuous morphologies arising a result of the microphase separation in block copolymer melts have so far never been observed self-assembled in systems of particles with spherically symmetric interaction. We report a molecular dynamics simulation of two simple one-component liquids which self-assemble upon cooling into equilibrium orthorhombic continuous network morphologies with the Fddd space group symmetry reproducing the structure of those observed in block copolymers. The finding that the geometry of constituent molecules isn't relevant for the formation of triply periodic networks indicates the generic nature of this class of phase transition.

Nanoporous crystals are widely studied and used for applications in $$\mathrm{H_{2}}$$ storage, $$\mathrm{CO_{2}}$$ capture, petrochemical catalysis and many other applications, yet the imaging of their atomic structure has proven difficult because of their radiation sensitivity and the small size of these microcrystals. This chapter describes the development of the new modes of electron microscopy needed to study them, and compares these with traditional methods such as x-ray diffraction. This class of materials has traditionally been dominated by the zeolites and zeotype materials, but has recently been expanded to include meso-/macroporous crystals and other new framework structures (MOFs, ZIFs COFs, etc.). Using different building blocks or units, versatile crystal structures have been synthesized for various applications. Their properties and functions are governed primarily by periodic arrangements of pores and/or cavities and their surroundings with various atomic moieties inside crystals. In this chapter, electron microscopy studies of nanoporous materials are discussed from different perspectives. Special attention is paid to the observation of fine defect structures, through careful analysis of electron diffraction, high-resolution images and spectroscopy data. The experimental conditions for imaging beam-sensitive materials, such as MOFs, are described. The contents have been divided into sections based on the types of materials and their geometric features. Examples of structure analysis of various nanoporous materials are given and discussed. New technical developments and existing challenges are described.

Capture of trace amounts (parts per trillion or ppt level) of 90Sr from highly Na+-rich (5 M or 115 000 parts per million) liquid wastes produced from reprocessing of spent nuclear fuel rods is crucial for continuous operation of nuclear power plants.

Chiral crystals can be exploited for applications in enantioselective separation and catalysis. However, the study of chirality at the atomic level in a sub-micrometre-sized crystal is difficult due to the lack of adequate characterization methods. Herein, we present two efficient and practical methods of characterization that are based on electron crystallography. These methods are successfully applied to reveal the handedness of a chiral, zeolite nanocrystal. The handedness is identified through either a comparison of two high-resolution transmission electron microscope images, taken from the same nanocrystal but along different zone axes by tilting it around its screw axis, or the intensity asymmetry of a Bijvoet pair of reflections in a single precession electron-diffraction pattern. These two approaches provide new ways to determine the handedness of small, chiral crystals.

A three-dimensional covalent organic framework (COF-505) constructed from helical organic threads, designed to be mutually weaving at regular intervals, has been synthesized by imine condensation reactions of aldehyde functionalized copper(I)-bisphenanthroline tetrafluoroborate, Cu(PDB)(2)(BF4), and benzidine (BZ). The copper centers are topologically independent of the weaving within the COF structure and serve as templates for bringing the threads into a woven pattern rather than the more commonly observed parallel arrangement. The copper(I) ions can be reversibly removed and added without loss of the COF structure, for which a tenfold increase in elasticity accompanies its demetalation. The threads in COF-505 have many degrees of freedom for enormous deviations to take place between them, throughout the material, without undoing the weaving of the overall structure.

The crystalline structure of UTL zeolite experienced an unusual orientated collapse and reconstruction within an extremely narrow time window during the structural stabilization process by nitric acid treatment at elevated temperature. Taking full advantage of this unique structural change, extra-large pore Sn-UTL zeolites were postsynthesized via the reaction between the SnCl4 molecules and the silanols in the hydroxyl nests, which occurred concomitantly with the removal of Ge and/or Si species from the dense layer. The original UTL topology was restored thereafter, leading to a Sn-incorporated analogue. The usage of the most seriously collapsed intermediate structure, which was captured by timing during the precisely controlled acid treatment, was vital for achieving Sn-UTL zeolites with a larger amount of isolated Sn species effectively incorporated. With tetrahedrally coordinated Sn ions in the highly stabilized UTL topology consisting of intersecting 12- and 14-membered ring (MR) pore channels, Sn-UTL showed promising catalytic performance in the Meerwein-Pondorf-Verley reaction as well as in the Baeyer-Villiger oxidation reactions of ketones using H2O2 or even bulky tert-butyl hydroperoxide (TBHP) as an oxidant.

We report a solid smectic phase that exhibits dodecagonal global order. It is composed of axially stacked hexagonally ordered particle layers, and its 12-fold rotational symmetry induced by the 30° rotation of adjacent layers with respect to each other. A quasicrystal was produced in a molecular-dynamics simulation of a single-component system of particles interacting via a spherically-symmetric potential. It was formed as a result of a first-order phase transition from an isotropic liquid state that occurred under constant-density cooling. This finding implies that a similarly structured quasicrystal can possibly be produced by the same class of systems as those forming smectic-B crystals. This quasicrystal can also be expected to arise in a system of spherically-shaped colloidal particles with appropriately tuned potential.

During the reprocessing of spent nuclear fuel rods, a highly moist off-gas mixture containing various volatile radioactive species, such as iodine (I2), organic iodides and nitric acid, is produced.