Development of a novel cathodic deposition method for thin-film metal azolate frameworks toward Cd2+ adsorption.

Metal-Organic Frameworks (MOFs) have attracted much attention due to its large specific surface, flexible porosity and unsaturated coordination bonds. Cathodic deposition is a unique in-situ potential-driven synthesis method for the deposition of thin film MOFs; however, the gradually consumption of reactants during cathodic deposition might lead to unstable and uncontrollable reaction during thin-film MOF deposition. Herein, oxygen is selected as the initial reactant for the formation of OH−, which can result in gradually and successive formation of thin-film MAF-66 (Metal azolate framework-66), and the particle size and film thickness of the MAF-66 film can be easily tuned by the deposition time. Furthermore, the cathodic deposited thin-film MAF-66 show good adsorption property for heavy metal ions, with Cd2+ as a representative species. The adsorption capacity can reach 32.3 ​mg/g (removal ratio: 69%) and the deposited MAF-66 film can achieve a satisfactory recovery degree with structural and morphological stability. In this way, a novel, environmental-friendly, and controllable cathode deposition method is developed for preparation of thin-film MAF-66, which also show great promise as a candidate for heavy metal ions adsorbent. Schematic illustration of the cathodic deposition of thin-film MAF-66 and its application for Cd2+ Adsorption. [Display omitted] • A simple, environmental friendly, and sustainable cathode deposition method is developed to prepare MAF-66 film. • The particle size and film thickness of MAF-66 film can be easily tuned. • The MAF-66 film exhibits good adsorption capacity toward Cd2+ adsorption. [ABSTRACT FROM AUTHOR]