Journal Article

Reversible colossal barocaloric effect dominated by disordering of organic chains in (CH3–(CH2)n−1–NH3)2MnCl4 single crystals

Wang, Yangxin, Tian, Zhengying, Zhang, Cheng, Liu, Xingzheng, Chen, Yunzhong, Hao, Jiazheng, Yin, Zhuo, Huang, Qingzhen, Li, Yunliang, Shi, Youguo, Lin, Yuan, Shen, Feiran, Zhao, Tongyun, Song, Hongyan, Gao, Yihong, Sun, Jirong, Liu, Hongxiong, Zhang, Hao, Yu, Zibing, Wang, Jing, Hu, Fengxia, Song, Youting, Wang, Bingjie, Zhou, Houbo, Shen, Baogen

2022

Overview

Solid-state refrigeration based on the caloric effect is viewed as a promising efficient and clean refrigeration technology. Barocaloric materials were developed rapidly but have since encountered a general obstacle: the prominent caloric effect cannot be utilized reversibly under moderate pressure. Here, we report a mechanism of an emergent large, reversible barocaloric effect (BCE) under low pressure in the hybrid organic–inorganic layered perovskite (CH 3 –(CH 2 ) n −1 –NH 3 ) 2 MnCl 4 ( n  = 9,10), which show the reversible barocaloric entropy change as high as Δ S r ∼ 218, 230 J kg −1  K −1 at 0.08 GPa around the transition temperature ( T s ∼ 294, 311.5 K). To reveal the mechanism, single-crystal (CH 3 –(CH 2 ) n −1 –NH 3 ) 2 MnCl 4 ( n  = 10) was successfully synthesized, and high-resolution single-crystal X-ray diffraction (SC-XRD) was carried out. Then, the underlying mechanism was determined by combining infrared (IR) spectroscopy and density function theory (DFT) calculations. The colossal reversible BCE and the very small hysteresis of 2.6 K (0.1 K/min) and 4.0 K (1 K/min) are closely related to the specific hybrid organic–inorganic structure and single-crystal nature. The drastic transformation of organic chains confined to the metallic frame from ordered rigidity to disordered flexibility is responsible for the large phase-transition entropy comparable to the melting entropy of organic chains. This study provides new insights into the design of novel barocaloric materials by utilizing the advantages of specific organic–inorganic hybrid characteristics. Solid-state coolants: Hybrid crystals deliver big chills at low pressures Materials that can absorb and release heat under low mechanical pressure hold promise for high-efficiency refrigeration technology. Recent studies have shown that significant compression-induced cooling effects at low pressures can be achieved using crystals known as perovskites containing layers of organic chains and metal cations. Yihong Gao from the Chinese Academy of Sciences in Beijing and colleagues have now uncovered the mechanism underlying the thermal response of layered perovskites. Using a combination of x-rays, spectroscopy and theoretical calculations, the team discovered how the crystal structure changes at different temperatures. Their experiments revealed a low-energy phase transition where organic chains transform from rigid states to highly flexible conformations held in place by metallic layers. The large entropy change associated with this transition and its reversible nature could aid in the design of other organic–inorganic solid-state coolants. For the emergent colossal, reversible barocaloric effect in organic–inorganic perovskite hybrids (CH 3 –(CH 2 ) n −1 –NH 3 ) 2 MnCl 4 ( n  = 9, 10), we successfully grew a single crystal, and the underlying mechanism was determined by high-resolution SC-XRD, IR spectroscopy and DFT calculations. The drastic transformation of organic chains confined to the metallic frame from ordered rigidity to disordered flexibility is responsible for the large phase-transition entropy, which is comparable to the melting entropy of organic chains. The result provides new insights into designing novel barocaloric materials by utilizing the disordering of organic chains of organic–inorganic hybrid materials.

• Publisher: Springer Japan,Nature Publishing Group
• Subject: 119/118 / 639/301/119/2795 / 639/301/119/996 / 639/301/299/921 / Ammonia / Biomaterials / Chains / Chemistry and Materials Science / Chills / Coolants / Cooling effects / Crystal structure / Crystals / Density functional theory / Energy Systems / Entropy / Infrared spectroscopy / Low pressure / Materials Science / Mathematical analysis / Optical and Electronic Materials / Perovskites / Phase transitions / Pressure effects / Refrigeration / Single crystals / Solid state / Spectrum analysis / Structural Materials / Surface and Interface Science / Thermal response / Thin Films / Transition temperature