Chemically Modulated Microwave-Assisted Synthesis of MOF-74(Ni) and Preparation of Metal–Organic Framework-Matrix Based Membranes for Removal of Metal Ions from Aqueous Media

In this study, microwaves and chemical modulators were used in combination to improve the uniformity of synthesized MOF-74(Ni) materials. A segmented flow, microwave-assisted reactor was used where rapid nucleation in the microwave zone was separated from growth processes in an oil bath. High temperatures in the microwave zone induce fast nucleation, which can result in the formation of polydisperse products through agglomeration that reduces the available surface area. Benzoic acid was used as a chemical modulator where higher benzoic acid to Ni2+ concentration ratios resulted in a substantial increase in apparent reaction activation energies for short reaction times (∼1 s). Optimization of the synthetic process resulted in MOF-74(Ni) particles with high crystallinity, high surface area, and narrow particle size distributions. These synthesized MOF-74(Ni) particles were used to prepare metal–organic framework-Nafion matrix based membranes to investigate the removal of metal ions from aqueous solutions with high efficiencies.