Optimisation of the synthesis of MOF nanoparticles made of flexible porous iron fumarate MIL-88A

The synthesis of nanoparticles of the porous flexible iron fumarate MIL-88A (MIL stands for Materials from Institut Lavoisier) has been studied through the use of several synthetic routes using non-toxic solvents. Hydro-solvothermal synthesis under dynamic or static, ambient or autogenous pressure conditions, assisted or not by microwave irradiation or ultrasonic methods have been compared in terms of particle size, polydispersity and yield. Different parameters such as temperature, time, concentration, pH or the use of additives (base, inhibitor) were evaluated. The resulting nanoparticles were characterised using X-ray powder diffraction (XRPD), dynamic light scattering (DLS), transmission and scanning electron microscopy (TEM and SEM) and the yield of the reaction was estimated. Although significant amounts of small nanoparticles (∼200 nm) were obtained from each synthetic route, most conditions led to an important polydispersity. Ultrasonic synthesis led, on the contrary, to very low yields of small and monodisperse nanoparticles. Finally, only microwave assisted hydrothermal synthesis afforded the successful fast synthesis of high yields of small (<100 nm) and monodispersed nanoparticles.