Rapid and selective adsorption of gold ions with hydroxyl-functionalized UiO-66-type metal–organic frameworks

Abstract

With the wide application of gold as a high-value resource, the recycling of gold has received considerable attention. Owing to the functional active sites, tunable pore size and designable structures, metal–organic frameworks (MOFs) have aroused significant curiosity in gold-recycling. However, designing MOFs with both remarkable adsorption capacity and selectivity for Au(III) is highly desirable but challenging. In this work, two hydroxy-modified UiO-66-type MOFs: UiO-66-(OH)₂ and UiO-66-OH have been prepared for rapid and selective adsorption of gold ions from aqueous solution. Significantly, UiO-66-(OH)₂ was found to exhibit a remarkable gold adsorption capacity of 1570 mg g⁻¹ (pH = 6) compared with UiO-66-OH (520 mg g⁻¹) under uniform conditions. Furthermore, UiO-66-(OH)₂ still exhibited excellent gold adsorption efficiency in the presence of other interfering ions. Mechanism analyses revealed that Au(III) was partly transformed to Au(0) by the reducing action of –OH on the framework in the gold adsorption process. Importantly, the MOF materials can be well regenerated by soaking in hydrochloric acid–thiourea aqueous solution.