To improve the stability of MOF catalysts, a design of MOF@mesoporous SiO 2 yolk-shell nanoreactors was developed via a mesoporous silica coating followed by selective water-etching strategy. Benefiting from their permeable mesoporous SiO 2 shells, exposed active sites on MOF surfaces, and protective shells, the yolkshell nanoreactors exhibit higher catalytic stability than bare MOF crystals in CO 2 cycloaddition, with product yield remaining unchanged upon three cycles.

Zeolites are widely used in catalysis, gas separation, ion exchange, etc. due to their superior physicochemical properties, which are closely related to specific features of their framework structures. Although more than two hundred different framework types have been recognized, it is of great interest to explore from a crystallographic perspective, the atomic positions, surface terminations, pore connectivity and structural defects that deviate from the ideal framework structures, namely local structural modulation. In this article, we review different types of local modulations in zeolite frameworks using various techniques, especially electron microscopy (EM). The most recent advances in resolving structural information at the atomic level with aberration corrected EM are also presented, commencing a new era of gaining atomic structural information, not only for all tetrahedral atoms including point vacancies in framework but also for extra‐framework cations and surface terminations.

Among homologous series of metal oxides, Andersson‐Magnéli phases TinO2n‐1 (n=4–10) have attracted renewed scientific attention because of their behaviour in electrical conductivity and chemical/thermal stability. Various applications have also been reported for the phases with different values of n, or slightly reduced rutile (TiO2). The characteristic properties of these materials depend strongly on the compositional deviation from TiO2 and the way in which the structure accommodates the deviation. Thus, an urgent requirement is to overcome difficulties in characterizing such materials at atomic resolution. Here, we trace the discovery of the Andersson‐Magnéli phases, and report the application of recent developments in electron microscopy to reveal the relation, at the local level, between structural characteristics and electronic states, specifically for the materials TinO2n‐1 with n=4–8. The electrical conductivity of Ti4O7 has been reported previously to show three clearly distinct states on decreasing temperature from 300 K. For this reason, we focus on Ti4O7 as a representative example of the TinO2n‐1 phases and report structural characteristics at temperatures corresponding to each of the three different phases, focusing on the distribution of Ti3+ and Ti4+ cations from analysis of single‐crystal XRD data. Electron diffraction experiments and electrical conductivity measurements are also reported.

Defects within zeolites are crucially important for explaining their physicochemical behavior. The UTL zeolite, with a pillared layer structure, has been widely used in zeolite crystal engineering to assemble new structures from its layered structural units, but a fundamental understanding of its defect is lacking. Here, we report a newly synthesized UTL framework zeolite, UTL-DBU, with a commercially available superbase 1,8-diazabicyclo[5.4.0]­undec-7-ene (DBU) as a template. Its structure was determined by a combination of three-dimensional electron diffraction tomography and high-resolution (scanning) transmission electron microscopy. Using transmission electron microscopy, two types of defects, stacking disorder and edge dislocation-like planar defect, were discovered. On the basis of the analysis of the electron diffraction and imaging, the layer stacking sequence together with the structural and mathematical models of the microtwinning was successfully built up. Unraveling these defects will provide new insights into the rational design of targeted zeolites utilizing UTL.

Phase transitions of materials are usually accompanied by a remarkable change of properties. Tracing and identifying the structural changes at the atomic scale is the key to understanding the fundamental mechanisms behind their performances. However, the direct observation of three-dimensional structural transformations in single nanocrystals has been rarely achieved. Herein we reported the development of an in situ threedimensional electron diffraction (3D ED) approach for single nanocrystal structural analysis by combining 3D ED with in situ transmission electron microscopy. Each data set covering a crystal tilting range of 50°was collected in around 1 min at the set temperature using an in situ heating holder. The feasibility of this protocol was proved by its successful application in investigating the metal−insulator transition (MIT) of vanadium dioxide (VO 2 ) crystals with atomic precision. Moreover, local domains were found in the monoclinic phase before and after the annealing process, of which the orientations obey a 4-fold rotation symmetry along the a-axis.

Zeolites are widely used in catalysis, gas separation, ion exchange, etc. due to their superior physicochemical properties, which are closely related to specific features of their framework structures. Although more than two hundred different framework types have been recognized, it is of great interest to explore from a crystallographic perspective, the atomic positions, surface terminations, pore connectivity and structural defects that deviate from the ideal framework structures, namely local structural modulation. In this article, we review different types of local modulations in zeolite frameworks using various techniques, especially electron microscopy (EM). The most recent advances in resolving structural information at the atomic level with aberration corrected EM are also presented, commencing a new era of gaining atomic structural information, not only for all tetrahedral atoms including point vacancies in framework but also for extra‐framework cations and surface terminations.

No abstract

Motivated by the successful synthesis of two-dimensional diamane [Nat. Nanotechnol. 2020, 15, 59-66], in this work, the electronic and optical properties of diamane with molecular adsorption are investigated by first-principles calculation. Based on the surface transfer doping mechanism, we report the degenerate p-type and n-type doping for hydrogenated diamane (H-diamane) and fluorinated diamane (F-diamane), respectively. Hole accumulation on H-diamane and degenerate levels in the density of states (DOS) are found when organic molecules (tetracyanoethylene, tetracyanoquinodimethane, and tetrafluorotetracyanoquinodimethane) and transition-metal oxides (MoO 3 , CrO 3 , WO 3 , V 2 O 5 , and ReO 3 ) are chosen as acceptors on H-diamane. Conversely, F-diamane shows electron accumulation and degenerate levels in DOS when organic molecules (decamethylcobaltocene and cobaltocene 2 ) are adsorbed. The carrier concentration values of H-diamane and F-diamane are 1.91 × 10 13 to 3.96 × 10 13 cm −2 and 1.96 × 10 13 to 3.38 × 10 13 cm −2 , respectively. After adsorption, the optical absorption increases significantly in the visible-light region. Our findings would provide a feasible route to modulate the electronic and optical properties of diamane.