Mechanical energy storage performance of an aluminum fumarate metal–organic framework† Pascal G. Yot, * a Louis Vanduyfhuys, b Elsa Alvarez, cd Julien Rodriguez, e Jean-Paul Iti ´ e, f Paul Fabry, c Nathalie Guillou, c Thomas Devic, c Isabelle Beurroies, f Philip L. Llewellyn, f Veronique Van Speybroeck, b Christian Serre c and Guillaume Maurin a The aluminum fumarate MOF A520 or MIL-53–FA is revealed to be a promising material for mechanical energy-related applications with performances in terms of work and heat energies which surpass those of any porous solids reported so far. Complementary experimental and computational tools are deployed to finely characterize and understand the pressure-induced structural transition at the origin of these unprecedented levels of performance. 1. Introduction Metal organic frameworks (MOFs) have aroused a great interest over the past decade not only for the wide spectrum of materials that can be synthesized but also for their potential use in societally-relevant applications. 1 While much effort has been focused on the design of MOFs for gas storage/separation, 1 much less attention has been paid to tuning their mechanical energy storage performance. 2–10 Indeed, very few hydrophobic MOFs have been reported to absorb relatively high amounts of energy during water intrusion–exclusion cycles. 9,10 Flexible MOFs have been proposed as potential nano-dampers or shock absorbers since their pressure-induced structural transitions in forming a contracted phase can generate relatively high work energy during compression/decompression cycles. 2–8 In partic- ular, Hg-porosimetry and high-pressure X-ray diffraction experiments revealed that the carboxylate-based MIL-53 series 2,4,7,8 rival or even surpass mesoporous silica and zeolites 9–13 in terms of mechanical energy stored. Very recently, signicant improvements have been made to the crystallinity of the commercialized aluminum fumarate A520 14–18 via an opti- mized synthesis route which rendered possible the resolution of the crystal structure of this solid in its hydrated form. This solid, denoted as MIL-53(Al)–FA, was revealed to be isoreticular of the well documented highly exible MIL-53(Al)–BDC (BDC ¼ 1,4- benzenedicarboxylate) with a slightly smaller pore dimension (7.3  7.7 ˚ A 2 vs. 8.5  8.5 ˚ A 2 ), 19 and interestingly a rigid char- acter upon water sorption. Following the strong shi to higher pressure observed previously for the structural transition when turning from highly exible MIL-53(Cr, Al) solids to the ‘sorp- tion rigid’ parent MIL-47(V IV ) analogue, 4 we assumed here that one could use the Al fumarate features as an attractive candi- date to maximize the work energy (W ¼ P  DV) absorbed during one compression–decompression cycle through an ex- pected increase in the structural transition pressure (P) while maintaining a relatively high volume variation (DV). 1 Hg-porosimetry and in situ high-pressure synchrotron X-ray powder diffraction coupled with molecular simulations conrmed that the dehydrated version of MIL-53(Al)–FA shows a reversible structural contraction (Fig. 1) under an applied pressure above 100 MPa. This leads to a very high work energy of 60 J g 1 that considerably exceeds the values reported so far for other porous solids. 2–13 This unprecedented level of perfor- mance is maintained with the use of silicon oil, a more envi- ronmentally friendly uid, to perform the compression– decompression cycles. A direct measurement of the heat energy conrms the great promise of this low-cost and stable MOF for such an application. 2. Material and methods Powder of the aluminum fumarate metal–organic framework MIL-53–FA has been prepared following the optimized synthesis route very recently reported by Alvarez et al. 18 The pressure-induced structural response of both the dehydrated a Institut Charles Gerhardt Montpellier UMR 5253 CNRS UM ENSCM, Universit´ e de Montpellier, CC 15005, Place Eug` ene Bataillon, F-34095 Montpellier cedex 05, France. E-mail: pascal.yot@umontpellier.fr; Fax: +33 4 67 14 42 90; Tel: +33 4 67 14 32 94 b Centre for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde, Belgium c Institut Lavoisier Versailles, UM 8180, Universit´ e de Versailles St-Quentin, 45, avenue des Etats-Unis, F-78035, Versailles cedex, France d PSA Peugeot Citro¨ en – Direction Scientique et Technologies Futures, DSTF/SEPC/ STEP, Route de Gisy – 78943, Velizy-Villacoublay cedex, France e Aix-Marseille Universit´ e, CNRS, MADIREL (UMR 7246), Centre Scientique de St. J´ erˆ ome, F-13397, Marseille cedex 20, France f Synchrotron Soleil, L'orme des Merisiers, Saint-Aubin – BP 48, F-91192 Gif-sur-Yvette cedex, France † Electronic supplementary information (ESI) available: Experimental procedures, X-ray diffraction, and molecular simulation. See DOI: 10.1039/c5sc02794b Cite this: Chem. Sci. , 2016, 7, 446 Received 30th July 2015 Accepted 2nd October 2015 DOI: 10.1039/c5sc02794b www.rsc.org/chemicalscience 446 | Chem. Sci. , 2016, 7, 446–450 This journal is © The Royal Society of Chemistry 2016 Chemical Science EDGE ARTICLE Open Access Article. Published on 05 October 2015. Downloaded on 5/16/2022 9:25:43 PM. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. View Article Online View Journal | View Issue