Preparation of Highly Porous Metal–Organic Framework Beads for Metal Extraction from Liquid Streams

Abstract

Metal–organic frameworks (MOFs) offer great promise in a variety of gas- and liquid-phase separations. However, the excellent performance on the lab scale hardly translates into pilot- or industrial-scale applications due to the microcrystalline nature of MOFs. Therefore, the structuring of MOFs into pellets or beads is a highly solicited and timely requirement. In this work, a general structuring method is developed for preparing MOF–polymer composite beads based on an easy polymerization strategy. This method adopts biocompatible, biodegradable poly­(acrylic acid) (PAA) and sodium alginate monomers, which are cross-linked using Ca2+ ions. Also, the preparation procedure employs water and hence is nontoxic. Moreover, the universal method has been applied to 12 different structurally diverse MOFs and three MOF-based composites. To validate the applicability of the structuring method, beads consisting of a MOF composite, namely Fe–BTC/PDA, were subsequently employed for the extraction of Pb and Pd ions from real-world water samples. For example, we find that just 1 g of Fe–BTC/PDA beads is able to decontaminate >10 L of freshwater containing highly toxic lead (Pb) concentrations of 600 ppb while under continuous flow. Moreover, the beads offer one of the highest Pd capacities to date, 498 mg of Pd per gram of composite bead. Furthermore, large quantities of Pd, 7.8 wt %, can be readily concentrated inside the bead while under continuous flow, and this value can be readily increased with regenerative cycling.

From metal–organic framework powders to shaped solids: recent developments and challenges

“…Farrusseng et coll. [147] Finally, Yang et al [148] prepared polydopamine-grafted Fe-BTC-based beads for the extraction of lead from Rhône river water (600 ppb). Under continuous flow, one gram of beads could reduce the concentration of 10.8 liters of water below the EPA limit of 15 ppb.…”

“…Consequently, the water sorption capacity of the MOF-based beads was reduced by the 68 same extent, suggesting no pore blocking caused by the polymer. Importantly, the alginate content in the beads also had no significant impact on mass and heat transfers.Yang et al[148] modified the "alginate" method by adding an extra cross-linker agent: the polyacrylic acid (PAA). Interestingly, this polymer presents a large molecular weight and rapidly polymerizes, limiting the polymers ability to diffuse into the MOFs porosity.…”

Synthesis, crystal structure and magnetic properties of poly[[diaqua{μ6-2-[bis(carboxylatomethyl)amino]terephthalato}dicobalt(II)] 1.6-hydrate]

“…Over the last two decades, coordination polymers (CPs) have become one of the most attractive fields in chemistry because of their fascinating structures and promising applications as solid functional materials in adsorption and separation (Gan et al, 2020;Yang et al, 2020;Qian et al, 2020;Islamoglu et al, 2020), catalysis (Bavykina et al, 2020), sensing (Allendorf et al, 2020), luminescence (Rice et al, 2020) and magnetism (Thorarinsdottir & Harris, 2020;Wang et al, 2019b). Multicarboxylic acids have been employed to synthesize compounds comprising of various dimensional structures such as chains, layers and three-dimensional frameworks.…”

Influence of carbohydrate polymer shaping on organic dye adsorption by a metal–organic framework in water

“…Therefore, the alginate polymer has been utilized as a shaping agent for a variety of adsorbents including MOFs. [26][27][28][29][30][31] The dye adsorption properties of unshaped and bead-shaped MIL were investigated using Orange II and Rhodamine B as dyes, which have different chemical structures and charges (Fig. 2).…”