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submitted on 22.06.2019 and posted on 24.06.2019by Timothée Stassin, Steve Waitschat, Niclas Heidenreich, Helge Reinsch, Finn Puschkell, Dmitry Kravchenko, Ivo Stassen, Jonas van Dinter, Rhea Verbeke, Marcel Dickmann, Werner Egger, Ivo Vankelecom, Dirk De Vos, Rob Ameloot, Norbert Stock
Energy-efficient indoors temperature control can be realised through adsorption chillers or adsorption heat pumps based on the reversible adsorption and desorption of water in porous materials. Stable microporous aluminium-based metal-organic frameworks (MOFs) present promising water sorption properties for this goal. The development of synthesis routes that make use of available and affordable building blocks and avoid the use of organic solvents is crucial to advance this field. In this work, two scalable synthesis routes under mild reaction conditions were developed for aluminium-based MOFs: (1) in aqueous solutions using a continuous flow reactor and (2) through the vapour-assisted conversion of solid precursors. Fumaric acid, its methylated analogue mesaconic acid, as well as mixtures of the two were used as linkers. The synthesis conditions determine the crystal structure (symmetry and topology), either the MIL-53 or MIL-68 type with square-grid or kagome-grid topology, respectively. Fine-tuning resulted in new MOF materials thus far inaccessible through conventional synthesis routes. Furthermore, by varying the linker ratio, the water sorption properties can be continuously adjusted while retaining the sigmoidal isotherm shape advantageous for heat transformation applications.
T.S., R.V. and I.S. thank the Research Foundation Flanders (FWO) for SB-PhD and postdoctoral fellowships (1S53316N, 1S00917N and 12L5417N). RA acknowledges the funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n° 716472, acronym: VAPORE), as well as the Research Foundation Flanders (FWO) for funding in the projects G083016N and 1501618N. This project was supported by the German Science Foundation (STO 643/10-1 and RE 4057/1-1) and the MATsynCELL project through the Röntgen-Ångström Cluster, financed by the Swedish Research Council and the German Federal Ministry of Education and Research (BMBF).