Steady-state electrochemical synthesis of HKUST-1 with polarity reversal

Abstract

Metal-organic frameworks (MOFs) are commonly synthesised in batch processes that are limited in size. Electrochemical synthesis is a promising method for producing MOFs on an industrial scale, however when using direct current (DC) product films can build up on electrodes causing passivation. This work investigates electrosynthesis of HKUST-1 using periodic polarity reversal (PR). The system was studied using electrochemical impedance spectroscopy (EIS); and scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to examine the product and electrode surfaces. PR experiments ran continuously for up to 60 h and demonstrated less electrode passivation than DC experiments. A conductive precipitate bridge formed between anode and cathode in DC experiments after 30 min, limiting further electrosynthesis. Between 3 h and 10 h synthesis times, PR achieved a production rate per electrode surface area of 1.83 mg h-1 cm-2 compared to 0.11 mg h-1 cm-2 from DC. Product produced using PR for 10 h and 60 h synthesis times resulted in BET surface areas of 1303 m2 g-1 and 1063 m2 g-1 respectively. PR outperformed DC electrosynthesis in this work, and may be beneficial for increasing the scale of MOF production if integrated into a continuous system.