Waste-derived CuNi-BDC bimetallic metal organic framework for photocatalytic wastewater treatment and hydrogen production

Abstract

A highly efficient CuNi-BDC bimetallic metal-organic framework (MOF) photocatalyst was synthesised via a hydrothermal method for enhanced photocatalytic hydrogen production, using BDC linkers derived from recycled waste PET bottles. The materials were characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Optical properties, including band gap energy and light-absorption behaviour, were evaluated using UV-Vis diffuse reflectance spectroscopy (UV-DRS). UV-DRS results showed that CuNi-BDC exhibited a reduced band gap and stronger visible-light absorption compared to its monometallic counterparts, contributing to its superior photocatalytic performance. The CuNi-BDC photocatalyst achieved 78% degradation of ciprofloxacin (CIP) under visible-light irradiation in 60 min, significantly outperforming the monometallic Cu-BDC at 59% and Ni-BDC at 55%. For photocatalytic water splitting, CuNi-BDC produced 27349.68 µmol g⁻¹ h⁻¹ of hydrogen, outperforming that of Cu-BDC at 24971.44 µmol g⁻¹ h⁻¹ and Ni-BDC at 23782.33 µmol g⁻¹ h⁻¹, which highlights its multifunctional capability. Comparative tests across diverse water matrices (tap, treated, rain, and sea water) confirmed the stability of CuNi-BDC, retaining over 70% of peak activity even in high-salinity conditions. It also exhibited excellent recyclability, maintaining high performance over six cycles in both hydrogen production and pollutant degradation. Overall, this study provides valuable insights into the development of sustainable, high-performance bimetallic MOFs synthesised from waste-derived organic linkers. The outstanding activity and stability of CuNi-BDC highlight its promise for dual applications in photocatalytic hydrogen production and the degradation of organic pollutants, contributing to cleaner energy generation and wastewater treatment technologies.