Meng-Juan Yang,Shu-Yu Tang,Yan-Ran Weng,Feng Zhou,Yu Shi,Yong-Ju Bai,Yong Ai
Hybrid organic–inorganic perovskites (HOIPs) have emerged as multifunctional materials with remarkable optical and electronic properties. In particular, 2D-layered lead iodide-based HOIPs possess great practical application potential in the photoelectric field. In this work, we report H/F substitution-induced 1D-to-2D increment of lead iodide HOIPs. The enantiomeric HOIPs, S- and R-FPPbI3 (FP = 3-fluoropyrrolidinium), were achieved by monofluoride substitution on the spacer cations of the parent HOIP, PyPbI3 (Py = pyrrolidinium), showing mirror image structural relationship and reversible solid-state phase transition. A 2D-layered HOIP, (DFP)2PbI4 (DFP = 3,3-difluoropyrrolidinium), was achieved with a low band gap of 2.09 eV through difluoride substitution, thanks to the expansion of the Pb–I network from 1D to 2D. This work highlights the exploration of 1D chiral and 2D-layered HOIP materials with reversible phase transitions through H/F substitution strategies.
Ning Song,Shao-Peng Chen,Xiao-Wei Fan,Yu-Hui Tan,Wen-Juan Wei,Yun-Zhi Tang
The molecular design and regulation has shown bright future for constructing smart molecular materials such as ferroelectrics, dielectric switches, electro-optic effect, and so forth. Here, by poly-H/F substitution in a simple organic-inorganic hybrid 2[CH2FCH2NH3]·[CdCl4], 1 (CH2FCH2NH3 = fluorine ethylamine cation), we obtained two novel hybrids, namely, 2[CHF2CH2NH3]·[CdCl4], 2 (CHF2CH2NH3 = 2,2′-difluorine ethylamine cation) and 2[CF3CH2NH3]·[CdCl4], 3 (CF3CH2NH3 = 2,2′,2″-trifluorine ethylamine cation). Further investigations show that compounds 1, 2, and 3 experience solid reversible phase transitions with temperatures at 294, 319, and 329 K respectively. These unique phase transitions were confirmed by their remarkable dielectric and heat anomalies around the phase transition temperatures. X-ray single-crystal diffraction analyses before and after the phase transitions show that the order–disorder motions of F atoms and the twist motions from the 2D [CdCl4]2– framework lead to these solid reversible phase transitions. Also, the Hirshfeld surface calculation of compounds 1, 2, and 3 suggests that the increasing ratio of the F···F interaction from the intermolecular interaction makes a major contribution for the substantial increase of their phase transition temperatures.
Yueyue He,Zhuo Chen,Xiaogang Chen,Xian-Ming Zhang,Dongying Fu
Organic–inorganic hybrid perovskite (OIHP) multifunctional molecular switching materials have been widely studied as excellent supplements to the conventional all-inorganic perovskites due to their structural diversity and property adjustability. However, considering their practical application, the phase transition temperature (Tp) of the system is a crucial evaluation standard and meanwhile it remains an arduous challenge to construct phase transition materials with three kinds of switching characteristics. Therefore, the design of high Tp multifunctional switching materials is a huge task. Herein, we have reported a chiral OIHP multifunctional semiconductor 2 ([(R)-N-fluoroethyl-3-quinuclidinol]PbBr3) with dielectric switching, nonlinear switching and ferroelastic switching characteristics and an ultrahigh Tp of 498 K, which is obtained from compound 1 ([(R)-N-ethyl-3-quinuclidinol]PbBr3) with a Tp of 445 K through the strategy of H/F substitution. The substitution of F atoms for H atoms not only changes the coordination environment of Pb, but also increases the molecular interactions due to the stronger electronegativity of the F atoms, which raises the barrier of rotation of the fluorinated organic cations, (R)-N-fluoroethyl-3-quinuclidinol, and finally leads to a remarkable increase in Tp. Ultimately, through accurate molecular design, the Tp of compound 2 has been increased by 53 K and compound 2 exhibits three kinds of switching characteristics, which also makes it a superior switching material for practical application.
危险品化学品经营许可证（带存储）