Adsorption-assisted photocatalytic degradation of methyl orange dye by zeolite-imidazole-framework-derived nanoparticles

Abstract

Zeolite-Imidazolate-Framework-8 (ZIF8) is a typical porous material obtained by strong coordination of Zn2+ ions with imidazole organic linkers. By judicious choice of constituents, ZIF8 can reveal a huge surface area, chemical stability, and well defined pore volume. In this work, well-synthesized ZIF8 exhibited the high adsorption capacity for methyl orange (MO) (19.4 mg of MO/g of ZIF8) via electrostatic, hydrogen bonding, and π-π interactions/stacking interactions. The irradiation of UV–visible light can induce the excitation of electrons in MO molecules. The excited states of MO∗ can have stronger interactions with the active sites of ZIF8 and results in more surface adsorption. Under UV light irradiation, the excited MO∗ was degraded by •OH radicals that were produced from ZIF8 via an excitation pathway. This was proved by the photoluminescence spectra of 2-hydroxyterephthalic acid that was converted from terephthalic acid reacted with •OH radicals. The calcined ZIF8 (ZnO) in air maintained the rhombic-dodecahedral shape and exhibited adsorption-assisted photocatalytic activity. Notably, Ag-loaded ZnO (Ag@ZnO) completely removed the MO dye within 120 min under simulated solar light. The zeolite-imidazole-framework (ZIF8) composites have been successfully developed as a promising multimodal platform for an excellent adsorbent and efficient photocatalyst. © 2020 Elsevier B.V.