Low-dimensional hybrid organic−inorganic perovskites (HOIPs) possess more localized electronic states and narrower conduction and valence bands to promote self-trapping of excitons and stronger exciton emission; therefore, they are widely used as building blocks for various applications in the fields of optoelectronics, photovoltaics, light-emitting diodes, luminescence, fluorescence, and so forth. Despite the past decades of intensive study, the discovered low-dimensional chiral HOIPs are rare as of the 1D chiral HOIP single crystals reported in 2003, as well as the low-dimensional chiral HOIP ferroelectrics are particularly scarce since the first chiral two-dimensional (2D) and/or one-dimensional (1D) HOIP ferroelectrics reported. Herein, two new low-dimensional HOIPs with the same conformational formula [R-MPA] 2 CdCl 4 (R-MPA + = (R)-(−)-1methyl-3-phenylpropylamine) were successfully synthetized by means of regulating the stoichiometric proportion of R-MPA and CdCl 2 in two ways of 1:1 (1) and 2:1 (2). By combining single-crystal X-ray diffraction, circular dichroism (CD) spectroscopy, differential scanning calorimetry, temperature-dependent dielectric constant, temperature-dependent second-harmonic generation (SHG) effect, polarization-dependent SHG response, and P−E hysteresis loop, we reveal that 1 is a 1D nonchiral molecular ferroelectric and 2 is the first zero-dimensional (0D) chiral ferroelectric with distinct CD signals; meanwhile, 2 exhibits increased properties of high-T c , large dielectric constant, SHG isotropy, and ferroelectricity than that of 1. These results not only shed light on the high tunability of the low-dimensional HOIP ferroelectrics but also open up an avenue to explore multifunctional chiral ferroelectrics.

An AIE gelator was used as a sensor to quantitatively detect both volatile acid and aromatic amine vapors.

Three-dimensional (3D) covalent organic frameworks (COFs) are a new type of crystalline organic porous material, which have great application potential in various fields due to their complex pore structures and fully exposed active sites. The synthesis of 3D COFs with novel topologies is still challenging on account of limited secondary building units. Herein, we report a 3D COF with hea topology, which has never been reported before, utilizing a D 3hsymmetric precursor [2,3,6,7,14,15-hexakis(4-formylphenyl)triptycene (HFPTP)] and [tetrakis(4-amino biphenyl)methane (TABPM)]. 3Dhea-COFs display permanent porosity and a Brunauer−Emmett− Teller surface area of 1804.0 m 2 g −1 . Owing to the huge internal free volume of triptycene, 3D-hea-COFs show good adsorption performance for H 2 , CO 2 , and CH 4 . Moreover, theoretical calculation reveals that both triptycene and tetraphenylmethane units contribute to enhance hydrogen storage capacity. The novel topology in this work expands the family of 3D COFs and provides new possibilities for designing efficient gas storage materials.

The fluorine-free chalcones and the chalcones bearing different numbers of fluorine atoms have been synthesized. It is found that fluorine can tune the reactivity of the photo-induced [2+2] cycloaddition reactions...

Two-dimensional (2D) hybrid lead halide perovskites have been extensively regarded as most promising candidates for application in solar cells and other optoelectronic devices. Although the power conversion efficiencies and environmental stability of 2D hybrid lead halide perovskites have rapidly improved, mechanical property studies of these materials are scarce. However, it contributes to fabricating mechanically stable or flexible devices. Herein, we report the mechanical properties of a 2D layered lead halide hybrid (C6H5CH2NH3)2PbCl4 by nanoindentation and first-principles calculations. The detailed discussion of the structure–property relationship demonstrates that the mechanical properties of (C6H5CH2NH3)2PbCl4 are anisotropic, and the organic components and van der Waals interactions between layers play a significant role in the structural stability of the 2D structure. Furthermore, the results of theoretical calculations suggest that 2D hybrid halide perovskites with an increase in the number of inorganic layers exhibit diminishing ductility when subjected to very large deformation. We further deduce that the substitution of organic parts with stiff and multifunctional organic components will lead to improved stability and carrier mobility of the perovskite solar cell absorber layer. These explorations shed light on routes to fabricate stable (flexible) and high-performance devices.

New diarylethene derivatives containing benzoxazole (NBO) and benzothiazole (NBT) have been synthesized. Light-induced trans-cis isomerization of NBO and NBT took place in crystals, and only induced the needle-like crystals of NBO to bend backwards away from the UV light source. The movement of the atoms was deemed to take place during the isomerization of NBO; hence, strain would be produced and accumulated rapidly in the surface of crystals exposed to UV light. The uniform release of strain led to the bending of needle-like crystals. The light-induced trans-cis isomerization efficiency of NBT was too low to drive the motion of crystals, which might have originated from the large repulsion between naphthyl and benzothiazole. These results provide a new platform for the transformation of light energy into mechanical energy in molecular crystals through the unimolecular photochemical reaction of diarylethene derivatives.

As a result of the extensive research and application of LiFePO4 (LFP) in the past > 20 years, there is now a relatively in-depth understanding of its structural stability, phase transition mechanism and electrochemical properties. However, the difficulties faced by further improving the performance of LFP due to its intrinsic low electronic and ionic conductivity have not yet been effectively solved. In order to unlock the effect of transition metal doping on the physicochemical properties of LFP, we establish doping models for all 3d, 4d and 5d transition metals in LFP and compare and analyze their structural properties, band gaps, formation energies, elastic properties, anisotropies and lithiation/delithiation voltages using ab-initio computational screening. According to our screening results, the V-, Mn-, Ni-, Rh- and Os-doped LFP structures have excellent electrochemical properties and can be used as high-performance cathode materials for Li-ion batteries.

When the A-and X-sites in three-dimensional (3D) ABX 3 -type organic−inorganic hybrid perovskites are occupied by organic molecules, the perovskites possess rich features and functionalities. Herein, we report a new hybrid organic−inorganic ABX 3 -type guanidinium hypophosphite perovskite, where its A-and Xsites are occupied by Gua cations and hypophosphite (H 2 POO − ) bridges, respectively, therefore displaying many excellent properties. Results show that it undergoes a second-order irreversible phase transition and exhibits a significant negative thermal expansion (NTE, α b (LT) = −7.7( 7) and α b (HT) = −20.5(1) MK −1 ) effect along the baxis. In addition, UV−vis absorption spectrum and calculated band structure and density of states demonstrate that the total structure donate to the large direct band gap. These results show that hypophosphite perovskites provide a promising platform for preparation of new functional materials.