Efficient Piezoelectric Energy Harvesting from a Discrete Hybrid Bismuth Bromide Ferroelectric Templated by Phosphonium Cation

Bismuth containing hybrid molecular ferroelectrics are receiving tremendous attention in recent years owing to their stable and non-toxic composition. However, these perovskite-like structures are primarily limited to ammonium cations. Herein, we report a new phosphonium based discrete perovskite-like hybrid ferroelectric with a formula [Me(Ph)₃P]₃[Bi₂Br₉] ( MTPBB ) and its mechanical energy harvesting capability. The Polarization-Electric field (P-E) measurements resulted in a well-defined ferroelectric hysteresis loop with a remnant polarization value of 2.1 μC cm⁻². Piezoresponse force microscopy experiments enabled visualization of the ferroelectric domain structure and evaluation of the piezoelectric strain coefficient (d₃₃) for an MTPBB single crystal and thin film sample. Furthermore, flexible devices incorporating MTPBB in polydimethylsiloxane (PDMS) matrix at various concentrations were fabricated and explored for their mechanical energy harvesting properties. The champion device with 20 wt % of MTPBB in PDMS rendered a maximum peak-to-peak open-circuit voltage of 22.9 V and a maximum power density of 7 μW cm⁻² at an optimal load of 4 MΩ. Moreover, the potential of MTPBB -based devices in low power electronics was demonstrated by storing the harvested energy in various electrolytic capacitors.     

Tunable Thermoelastic Anisotropy in Hybrid Bragg Stacks with Extreme Polymer Confinement

Controlling thermomechanical anisotropy is important for emerging heat management applications such as thermal interface and electronic packaging materials. Whereas many studies report on thermal transport in anisotropic nanocomposite materials, a fundamental understanding of the interplay between mechanical and thermal properties is missing, due to the lack of measurements of direction‐dependent mechanical properties. In this work, exceptionally coherent and transparent hybrid Bragg stacks made of strictly alternating mica‐type nanosheets (synthetic hectorite) and polymer layers (polyvinylpyrrolidone) were fabricated at large scale. Distinct from ordinary nanocomposites, these stacks display long‐range periodicity, which is tunable down to angstrom precision. A large thermal transport anisotropy (up to 38) is consequently observed, with the high in‐plane thermal conductivity (up to 5.7 W m^?1 K^?1) exhibiting an effective medium behavior. The unique hybrid material combined with advanced characterization techniques allows correlating the full elastic tensors to the direction‐dependent thermal conductivities. We, therefore, provide a first analysis on how the direction‐dependent Young's and shear moduli influence the flow of heat.     

A High‐Temperature Order–Disorder Phase Transition Coupled With Conformational Change in the Hybrid Material [C6H13NH]2⋅ZnBr4

A new high‐temperature, hybrid, phase‐transition material, 1‐methylpiperidinium tetrabromozincate ( 1 ), that shows a reversible transition at 345 K was synthesized. Differential scanning calorimetry and specific heat capacity measurements confirmed this reversible transformation with a large heat hysteresis of 25 K, which describes a typical first‐order phase transition in 1 . The dielectric constant exhibited a steplike anomaly and showed high and low dielectric states in the high‐ and room‐temperature phases, respectively, and therefore, this hybrid might be considered as a potential switchable dielectric material. The variable‐temperature powder X‐ray diffraction patterns displayed remarkable shifts between the experimental patterns at the two different phases. Single‐crystal X‐ray diffraction analyses at various temperatures revealed that the origin of this transformation could be attributed to disordering of the bromine atoms in the anion and the nitrogen atom of the cation. The cation also assumed a conformational change, which was likely induced by the disordered nitrogen atom. The conformational onset of the transformation of the cation from a planar conformer into a relaxed chair also occurred upon decreasing the temperature below transition point; thus, the combined order–disorder and conformational change induced the structural transformation and the change in symmetry.     

Phase Transitions in Three New Hybrid Crystals: (Me3NR)4[Ni(NCS)6] (R=Ethyl,Propyl, and Butyl)

Understanding the microscopic origin of phase transitions in hybrid crystals is of significant important but challenging for designing novel phase-transition materials. Here, three new hybrid crystals, (Me₃NR)₄[Ni(NCS)₆] (R=ethyl for 1 , propyl for 2 , and butyl for 3 ) were synthesized and comprehensively studied on their crystal structures, intermolecular interactions, and phase transitions. They possess a same anti-XeF₄ structure mode but exhibit different phase transitions arising from their subtly changed alkyl groups. Specifically, 1 undergoes four-step P2₁/c-P2₁/c-P2₁/c-Pbca-Cmce crystalline transitions at 165, 203, 244, and 280 K, respectively; 2 undergoes three-step P2₁2₁2₁-Pbca-P2₁/n-P 1c crystalline transitions at 167, 393, and 410 K, respectively, following by a solid-liquid transition at 453 K; 3 undergoes an iso-space-group P2₁/n-P2₁/n crystalline phase transition at 257 K and a solid-liquid transition at 410 K. These instances well demonstrate the key roles of delicate and complicated intermolecular interactions on inducing nontrivial phase transitions in hybrid crystals.     

A Thermally and Hydrolytically Stable Microporous Framework Exhibiting Single‐Chain Magnetism: Structure and Properties of [Co2(H0.67bdt)3]⋅20 H2O

Fixing a hole : Hydrothermal chemistry has been exploited in the preparation of a 3D framework material exhibiting 48 % accessible void volume and 1.5 % hydrogen uptake by weight at 120 kPa (see picture). The title compound also exhibits single‐chain magnetic behavior and reversible changes in magnetic properties upon solvation and desolvation.

     

[C6H14N]PbBr3: An ABX3‐Type Semiconducting Perovskite Hybrid with Above‐Room‐Temperature Phase Transition

Organic–inorganic hybrid perovskites, with the formula ABX₃ (A=organic cation, B=metal cation, and X=halide; for example, CH₃NH₃PbI₃), have diverse and intriguing physical properties, such as semiconduction, phase transitions, and optical properties. Herein, a new ABX₃‐type semiconducting perovskite‐like hybrid, (hexamethyleneimine)PbBr₃ ( 1 ), consisting of one‐dimensional inorganic frameworks and cyclic organic cations, is reported. Notably, the inorganic moiety of 1 adopts a perovskite‐like architecture and forms infinite columns composed of face‐sharing PbBr₆ octahedra. Strikingly, the organic cation exhibits a highly flexible molecular configuration, which triggers an above‐room‐temperature phase transition, at T_c=338.8 K; this is confirmed by differential scanning calorimetry (DSC), specific heat capacity (C_p), and dielectric measurements. Further structural analysis reveals that the phase transition originates from the molecular configurational distortion of the organic cations coupled with small‐angle reorientation of the PbBr₆ octahedra inside the inorganic components. Moreover, temperature‐dependent conductivity and UV/Vis absorption measurements reveal that 1 also displays semiconducting behavior below T_c. It is believed that this work will pave a potential way to design multifeatured perovskite hybrids by utilizing cyclic organic amines.     

[Al4(OH)2(OCH3)4(H2N‐bdc)3]⋅x H2O: A 12‐Connected Porous Metal–Organic Framework with an Unprecedented Aluminum‐Containing Brick

Al together now! A new stable aluminum aminoterephthalate system contains octameric building blocks that are connected by organic linkers to form a 12‐connected net (see picture). The structure adopts a cubic centered packing motive in which octameric units replace individual atoms, thus forming distorted octahedral (red sphere) and tetrahedral cages (green spheres) with effective accessible diameters of 1 and 0.45 nm, respectively.

     

Structure‐Triggered High Quantum Yield Luminescence and Switchable Dielectric Properties in Manganese(II) Based Hybrid Compounds

Two new manganese(II) based organic–inorganic hybrid compounds, C₁₁H₂₁Cl₃MnN₂ ( 1 ) and C₁₁H₂₂Cl₄MnN₂ ( 2 ), with prominent photoluminescence and dielectric properties were synthesized by solvent modulation. Compound 1 with novel trigonal bipyramidal geometry exhibits bright red luminescence with a lifetime of 2.47 ms and high quantum yield of 35.8 %. Compound 2 with tetrahedral geometry displays intense long‐lived (1.54 ms) green light emission with higher quantum yield of 92.3 %, accompanied by reversible solid‐state phase transition at 170 K and a distinct switchable dielectric property. The better performance of 2 results from the structure, including a discrete organic cation moiety and inorganic metal anion framework, which gives the cations large freedom of motion.     

(CH3NH3)2PdCl4: A Compound with Two‐Dimensional Organic–Inorganic Layered Perovskite Structure

The synthesis of previously unknown perovskite (CH₃NH₃)₂PdCl₄ is reported. Despite using an organic cation with the smallest possible alkyl group, a 2D organic–inorganic layered Pd‐based perovskites was still formed. This demonstrates that Pd‐based 2D perovskites can be obtained even if the size of the organic cation is below the size limit predicted by the Goldschmidt tolerance‐factor formula. The (CH₃NH₃)₂PdCl₄ phase has a bulk resistivity of 1.4 Ω cm, a direct optical gap of 2.22 eV, and an absorption coefficient on the order of 10⁴ cm^?1. XRD measurements suggest that the compound is moderately stable in air, an important advantage over several existing organic–inorganic perovskites that are prone to phase degradation problems when exposed to the atmosphere. Given the recent interest in organic–inorganic perovskites, the synthesis of this new Pd‐based organic–inorganic perovskite may be helpful in the preparation and understanding of other organic–inorganic perovskites.     

Design of Interpenetrated Networks of Mesostructured Hybrid Silica and Nonconductive Poly(vinylidene fluoride)–Cohexafluoropropylene (PVdF–HFP) Polymer for Proton Exchange Membrane Fuel Cell Applications

Organic–inorganic hybrid membranes of poly(vinylidene fluoride)–cohexafluoropropylene (PVdF–HFP) and mesostructured silica containing sulfonic acid groups were synthesized by using the sol‐gel process. These hybrid membranes were prepared by in situ co‐condensation of tetraethoxysilane and an organically modified silane (ormosil) by a self‐assembly route using organic surfactants as templates for tuning the architecture of the hybrid organosilica component. In this paper, we describe the elaboration and characterization of hybrid membranes all the way from the precursor solution to the evaluation of the fuel cell performances. These hybrid materials were extensively characterized by using NMR and IR spectroscopy, electron microscopy, or impedance spectroscopy so as to determinate their physicochemical and electrochemical properties. Even though the ion‐exchange capacity (IEC) was quite weak, the first fuel cell tests performed with these hybrid membranes show promising results relative to optimized Nafion 112 thanks to great water management of the silica inside the hydrophobic polymer.     

Synthesis,Structure and Photoluminescent Properties of [C6N2H14][Nd2(C2O4)2(SO4)2(H2O)4]·H2O,a New Organically Templated Neodymium(III) Oxalate‐sulfate

An organically templated neodymium oxalate–sulfate [C₆N₂H₁₄][Nd₂(C₂O₄)₂(SO₄)₂(H₂O)₄]·H₂O ( 1 ) has been synthesized under hydrothermal conditions and structurally characterized by single‐crystal X‐ray diffraction analysis. In 1 , the neodymium(III) ions are interconnected through oxalate and sulfate groups to form a neodymium oxalate–sulfate hybrid structure. A luminescence spectrum of 1 was recorded, and the luminescence decay time was also measured.