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

Abstract

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.

Understanding MOF Flexibility: An Analysis Focused on Pillared Layer MOFs as a Model System

“…Well‐documented examples are the flexible MOFs MIL‐53(Al) and functionalized versions thereof, [120] ZIF‐4(Zn) [121] and CUK‐1 [11c] . Some recent research highlights the tunability of the phase transition nature from discontinuous to quasi‐continuous in ZIF‐62(Zn) by linker functionalization [122] and reports about reentrant negative linear compressibility in MIL‐53(Al), which exhibits an NLC behaviour in the pressure region of 0–2.7 GPa, followed by a normal compression process between 2.7 and 12.9 GPa [123] …”

“…[11c] Some recent research highlights the tunability of the phase transition nature from discontinuous to quasi-continuous in ZIF-62(Zn) by linker functionalization [122] and reports about reentrant negative linear compressibility in MIL-53(Al), which exhibits an NLC behaviour in the pressure region of 0-2.7 GPa, followed by a normal compression process between 2.7 and 12.9 GPa. [123] More generally, flexible MOFs can show reversible and irreversible op to np/cp transitions accompanied by a volume reduction of up to 20 % upon the application of pressure, highlighting the relation between the structural chemistry of MOFs at high pressures and low temperatures. When irreversible, i.e.…”

Abnormal Compressive Behaviors of Metal–Organic Frameworks under Hydrostatic Pressure

“…For instance, the wine-rack unit consists of four Zn nodes bridged by −OCHO– linkers in [NH 4 ]­[Zn­(HCOO) 3 ], which exhibits NLC over the pressure range 0–0.94 GPa as a result of wine-rack motif deformation, as depicted in Figure b. The wine-rack mechanism also applies for the NLC behavior of MIL-53­(Al) and [Cu­(4,4′-bpy) 2 (H 2 O) 2 ]·SiF 6 , as shown in Figure c . Under compression, a typical wine-rack motif would expand along its longer diagonal and shrink along its shorter diagonal, giving rise to NLC and PLC along the two directions, respectively .…”

Giant Negative Linear Compressibility, Isosymmetric Phase Transition, and Breathing Effect in a 3D Covalent Organic Framework

“…This unique NLC remains valid over a relatively wide pressure range, emphasizing its significance. More interestingly, while NPN-3 does not show any phase transition or anomaly in the tensile region, NPN-3-hd shows a phase UTSA-16 (exp), 63 MFM-133 (Hf) (exp), 31 [(C 6 F 5 Au) 2 (μ-1,4diisocyanobenzene)] (exp), 64 [Fe(dpp)2(NCS)2]py (exp), 65 YFe-(CN) 6 (exp + DFT), 66 KMn[Ag(CN) 2 ] 3 (exp), 35 NPN-1 (DFT), 7 NH 2 -MIL-53 (AI) (exp + DFT), 28 MIL-53(AI) (exp + DFT), 27 [Ag(ethylenediamine)]NO 3 -I (exp), 67 Zn[Au(CN) 2 ] 2 -I (exp), 22 MCF-34 (exp + DFT), 32 In(BDC) 2 (exp), 29 transition from a closed pore to an open pore, exhibiting the breathing-like effect previously reported for many MOFs. The origins of these remarkable piezo-mechanical properties lie in the diamondoid topology, which is a structural element commonly found in flexible MOFs and COFs.…”

“…Figure 6. Reported framework materials showing the NLC effect.UTSA-16 (exp),63 MFM-133 (Hf) (exp),31 [(C 6 F 5 Au) 2 (μ-1,4diisocyanobenzene)] (exp),64 [Fe(dpp)2(NCS)2]py (exp),65 YFe-(CN) 6 (exp + DFT),66 KMn[Ag(CN) 2 ] 3 (exp),35 NPN-1 (DFT),7 NH 2 -MIL-53 (AI) (exp + DFT),28 MIL-53(AI) (exp + DFT),27 [Ag(ethylenediamine)]NO 3 -I (exp),67 Zn[Au(CN) 2 ] 2 -I (exp),22 MCF-34 (exp + DFT),32 In(BDC) 2 (exp),29 and Ag 3 [Co(CN) 6 ]-I (exp) 21. …”