Reentrant Negative Linear Compressibility in MIL-53(Al) over an Ultrawide Pressure Range

• Published in: Chemistry of materials 2022-03, Vol.34 (6), p.2764-2770
• Main Authors: Jiang, Dequan, Wen, Ting, Guo, Yanzhen, Liang, Jie, Jiang, Zimin, Li, Chen, Liu, Ke, Yang, Wenge, Wang, Yonggang
• Format: Article
• Language: English
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/acs.chemmater.1c04398

Anomalous compression behaviors such as negative linear compressibility (NLC) and negative area compressibility (NAC) are emerging functionalities essential for utilities under extreme conditions. Metal–organic frameworks (MOFs) present a large family of NLC/NAC materials under the well-recognized “wine-rack” mechanism. Nevertheless, the working pressure of MOFs is limited to typically no more than 3 GPa. Herein, we report the observation of a rare reentrant NLC behavior of MIL-53­(Al) over an ultrawide pressure region up to 41.6 GPa. MIL-53­(Al) with the classic wine-rack topology first exhibits an NLC behavior along the c-axis in the pressure region of 0–2.7 GPa, followed by a normal compression process between 2.7 and 12.9 GPa. After that, it is surprising to find that the reentrant NLC property remains at a record-high pressure (>40 GPa) among the previously reported MOFs. The mechanisms of the distinct compression behaviors of MIL-53­(Al) in the three stages are studied by combining the X-ray diffraction analyses, Raman spectra, and DFT calculation. Particularly, the photoluminescence of Cr3+ is used as a unique probe for the subtle changes of the local coordination environments of Al3+ under compression. Both the absorption spectra and photoluminescence of Cr3+-doped MIL-53­(Al) not only verify the three-stage compression processes but also reveal a hidden structural/electrical phase transition around 22.0 GPa. These findings provide an in-depth understanding of the structure–property relationship of abnormal compression behavior at the local-structure level.