Microwave-assisted fast synthesis of MOF-801

Abstract

The synthesis of MOF-801 was investigated using microwave (MW) heating. MW-assisted synthesis was used to heat the reaction mixture at 110 °C for 45 seconds only in a closed Teflon vessel using a 2.45 GHz fixed-frequency multimode MW cavity. The MW-synthesized MOF-801 was characterized using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), N2 gas adsorption measurements (BET), and dynamic vapor sorption (DVS). The prepared MOF-801 particles were in the nanoscale range, as revealed by SEM, TEM, and XRD. Furthermore, its typical cubic crystal structure with the space group Pn-3 (#201) was detected, as confirmed by the indexed XRD and FTIR patterns. The crystal sizes were calculated using the Scherrer equation for the (111) and (200) planes and found to be around 27 nm and 18 nm, respectively. The measured BET total specific surface area of the prepared powder was found to be 739.7 m²/g. Moreover, the TGA of the prepared materials showed excellent thermal stability. Additionally, SEM and TEM micrographs revealed the formation of the well-shaped octahedral fcu-MOF particles with a diameter of around 200 nm. MW-assisted synthesis of MOF-801 was successfully done in less than one minute with high phase purity, nano-crystal size, structural integrity, excellent thermal stability, a high surface area, and suitable water uptake capacity for water sorption applications. MW processing is considered a promising route for MOFs synthesis.

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