Electrochemical Synthesis of Some Archetypical Zn²⁺, Cu²⁺, and Al³⁺ Metal Organic Frameworks

Abstract

Several archetypical metal organic frameworks (MOFs), namely, HKUST-1, ZIF-8, MIL-100(Al), MIL-53(Al), and NH2-MIL-53(Al), were synthesized via anodic dissolution in an electrochemical cell. The influence of different reaction parameters such as solvent, electrolyte, voltage–current density, and temperature on the synthesis yield and textural properties of the MOFs obtained was investigated. The characterization of the samples involved X-ray diffraction, gas adsorption, atomic force microscopy, diffuse reflectance infrared Fourier transform spectroscopy, and scanning electron microscopy. In the present article, we demonstrate that electrochemical synthesis is a robust method offering additional degrees of freedom in the synthesis of these porous materials. The main advantages are the shorter synthesis time, the milder conditions, the facile synthesis of MOF nanoparticles, the morphology tuning and the high Faraday efficiencies. The synthesized MIL-53 and NH2-MIL-53 samples exhibit suppressed framework flexibility compared to samples synthesized solvothermally.

Electrosynthesis of Metal–Organic Frameworks: Challenges and Opportunities

“…[40] For HKUST-1, an increase in temperature led to as mall variation in surface area, although similar yields were obtained in all cases. Alteration of water/ethanol ratios had an effect similart ot hat reported by Denayer et al [57] for the formation of ad ense non-porous phase at high water content.…”

“…[39] It also provides the possibility to influence the reaction directly in real-time, offering both more control and the ability to perform the synthesis in ac ontinuous fashion. [40] Furthermore, the localised nature of electrochemical methods allows the formation of directed thin films without the need to pre-treat the surfacea si su sually the case. [41] The mild temperatures used during synthesis also reduce the effects of thermally induced film cracking, which is often ap roblem with hydrothermalmethods.…”

“…[66] Gascone tal.,s tudied the effect of temperature and choice of solvento nt he electrosynthesis of ZIF-8. [40] Surprisingly,Z IF-8 crystals wereo btained at temperatures as low as 0 8Cwith an even higherproduction rate. The high solubility of the linker (2-methylimidazole) also allowed the use of av ariety of solvents and supporting electrolytes (which have different conductivities).…”

“…[40] Named after the Materials Institute Lavoisier,t he selected MILs consist of carboxylate linkers anda luminium as metal nodes.…”

“…[40] Hydrogen evolution in the electrochemical cell results in ap Hi ncrease, which complicates the electrosynthesis of MIL-100 as it requires al ow pH. MIL-53(Al) contains terephthalica cid linkers, and crystallises into as tructure with diamond-shaped pores.…”