Aqueous Flow Reactor and Vapour-Assisted Synthesis of Aluminium Dicarboxylate Metal-Organic Frameworks with Tuneable Water Sorption Properties.

Timothée Stassin,Ivo Vankelecom,Finn Pluschkell,Marcel Dickmann,Dmitry Kravchenko,Steve Waitschat,Ivo Stassen,Helge Reinsch,João Marreiros,Rob Ameloot,Rhea Verbeke,Niclas Heidenreich,Jonas Dinter,Norbert Stock,Werner Egger,Dirk De Vos

doi:10.1002/chem.202001661

Abstract

Energy‐efficient indoors temperature and humidity control can be realised by using 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 to obtain polymorph materials with tuneable water sorption properties. The synthesis conditions determine the crystal structure and either the MIL‐53 or MIL‐68 type structure with square‐grid or kagome‐grid topology, respectively, is formed. 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 and room climatisation applications.

Highlights

The broad family of porous materials finds widespread use in catalysis,[1] adsorptive separations[2] and ion exchange,[3] among many other applications
We investigate the flow reactor and vapour-assisted synthesis of Al-MIL-53-Fum and related mixed-linker Al-metal–organic frameworks (MOFs) (Figure 1) to find efficient scalable preparation methods for materials with improved water sorption properties
The phase purity of both MOFs was confirmed by PXRD (Le Bail fits Figures S4.1 and S4.2 in the Supporting Information), the composition was confirmed by 1H NMR spectroscopy (Section S5 in the Supporting Information), elemental analysis (Section S6 in the Supporting Information), thermogravimetric analysis (Section S7 in the Supporting Information), IR spectroscopy (Section S8 in the Supporting Information) and the morphology was investigated by electron microscopy (Section S9 in the Supporting Information)

Summary

Introduction

The broad family of porous materials finds widespread use in catalysis,[1] adsorptive separations[2] and ion exchange,[3] among many other applications. We investigate the flow reactor (fr) and vapour-assisted (va) synthesis of Al-MIL-53-Fum and related mixed-linker Al-MOFs (Figure 1) to find efficient scalable preparation methods for materials with improved water sorption properties.

Results

Conclusion