Cost-effective 17O enrichment of metal–organic frameworks enables the composition and disorder in mixed-metal materials to be determined using NMR spectroscopy.

Recent research on piezoelectric materials is predominantly devoted to enhancing the piezoelectric coefficient, but overlooks its sign, largely because almost all of them exhibit positive longitudinal piezoelectricity. The only experimentally known exception is ferroelectric polymer poly(vinylidene fluoride) and its copolymers, which condense via weak van der Waals (vdW) interaction and show negative piezoelectricity. Here we report quantitative determination of giant intrinsic negative longitudinal piezoelectricity and electrostriction in another class of vdW solids—two-dimensional (2D) layered ferroelectric CuInP2S6. With the help of single crystal x-ray crystallography and density-functional theory calculations, we unravel the atomistic origin of negative piezoelectricity in this system, which arises from the large displacive instability of Cu ions coupled with its reduced lattice dimensionality. Furthermore, the sizable piezoelectric response and negligible substrate clamping effect of the 2D vdW piezoelectric materials warrant their great potential in nanoscale, flexible electromechanical devices.

Highly porous metal-organic frameworks (MOFs), which have undergone exciting developments over the past few decades, show promise for a wide range of applications. However, many studies indicate that they suffer from significant stability issues, especially with respect to their interactions with water, which severely limits their practical potential. Here we demonstrate how the presence of 'sacrificial' bonds in the coordination environment of its metal centres (referred to as hemilability) endows a dehydrated copper-based MOF with good hydrolytic stability. On exposure to water, in contrast to the indiscriminate breaking of coordination bonds that typically results in structure degradation, it is non-structural weak interactions between the MOF's copper paddlewheel clusters that are broken and the framework recovers its as-synthesized, hydrated structure. This MOF retained its structural integrity even after contact with water for one year, whereas HKUST-1, a compositionally similar material that lacks these sacrificial bonds, loses its crystallinity in less than a day under the same conditions.

Ionic conduction in a ferroelectric leads to anomalous polarization switching kinetics but prevents retention failure.

Ferroelastic-switching-driven large shear strain and piezoelectricity in a hybrid ferroelectric

ABSTRACT:The hydrothermal synthesis of a zeolite, with properties suitable for use in the ADOR (AssemblyDisassembly-Organisation-Reassembly) process, has been designed and a zeolite, called SAZ-1, successfully prepared. This zeolite has then been used as a parent in the ADOR process and two new daughter zeolites, IPC-15 and IPC-16, have been prepared. The X-ray powder diffraction patterns of the new zeolites match well those predicted using computational methods. The three materials, form an isoreticular series with decreasing pores size from 14-ring to 12-ring to 10-ring.

The assembly–disassembly–organization–reassembly (ADOR) process has been used to disassemble a parent zeolite with the UOV structure type and then reassemble the resulting layers into a novel structure, IPC‐12. The structure of the material has previously been predicted computationally and confirmed in our experiments using X‐ray diffraction and atomic resolution STEM‐HAADF electron microscopy. This is the first successful application of the ADOR process to a material with porous layers.

The Assembly-Disassembly-Organisation-Reassembly (ADOR) mechanism is a recent method for preparing inorganic framework materials and, in particular, zeolites. This flexible approach has enabled the synthesis of isoreticular families of zeolites with unprecedented continuous control over porosity, and the design and preparation of materials that would have been difficult -or even impossible -to obtain using traditional hydrothermal techniques. Applying the ADOR process to a parent zeolite with the UTL framework topology, for example, has led to six previously unknown zeolites (named IPC-n with n = 2, 4, 6, 7, 9 and 10). To realize the full potential of the ADOR method, however, a further understanding of the complex mechanism at play is needed. Here, we probe the disassembly, organisation and reassembly steps of the ADOR process through a combination of in situ solid-state nuclear magnetic resonance (NMR) spectroscopy and powder Xray diffraction (PXRD) experiments. We further use the insight gained to explain the formation of the intriguing structure of zeolite IPC-6.The recently-discovered ADOR process 1-4 has proved to be effective for the preparation of new silicate and aluminosilicate zeolites, providing routes to 'unfeasible' synthesis targets with novel structural features 3 and to families of isoreticular solids whose pore size can be precisely controlled over the whole range of zeolite porosity, from small pore all the way up to extra-large pore materials. 1,4 The process comprises four distinct steps. The assembly (A) process involves the preparation of a parent zeolite with suitable chemical and topological properties for