NH<sub>2</sub>-modification Copper Metal-organic Framework as a Sunlight Photocatalyst for the Removal of Organic Dyes from Aqueous Solution

Abstract

Dyes present in wastewater pose a threat to aquatic organisms and cannot be effectively eliminated by conventional biochemical treatment methods. As an alternative, the photocatalytic decolorization of dyes has emerged as a cost-effective and environmentally friendly approach. Two 1,3,5-benzenetricarboxylate (BTC)-based metal-organic frameworks (MOFs), CuBTC and CuBTC-NH2, were synthesized and used for the removal of two anionic dyes, namely Reactive Blue 171 and Acid Blue 1, from wastewater under sunlight irradiation. The structural and morphological characteristics of the MOFs were identified using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Compared to CuBTC, CuBTC-NH2 exhibited excellent photocatalytic activity. The successful degradation of 90% of the dyes was observed within 24 h of sunlight exposure using CuBTC-NH2, while only 70% degradation was achieved with CuBTC. The weak basic nature of the dye wastewater (pH 8-10) was found to facilitate the degradation process. CuBTC-NH2 was not only efficient in the removal of dyes but could also be recycled and reused for at least five cycles. In the process of photocatalytic degradation, the diazo bond of dyes in ortho-position to the amino substitution on the aromatic ring was attacked first. These results provide insights into the design of MOF catalysts for dye removal under visible-light irradiation.