Sustainable ZnO-MIL-101(Fe)/Graphene-like Carbon Ternary Photocatalyst Composite (ZMG) for Efficient Sunlight-Driven Methyl Orange Degradation

Abstract Addressing the urgent need to convert biomass waste into high-value functional materials, this study presents the synthesis of a sustainable ternary photocatalyst: ZnO-MIL-101(Fe)/Graphene-like carbon (ZMG). A central feature of this design is the strategic derivation of the graphene-like carbon (GLC) component from the abundant invasive biomass Phragmites australis, thereby aligning with Circular Economy principles. We evaluated the composite’s efficiency through the degradation of Methyl Orange (MO) under natural sunlight. Comparative evaluations demonstrated the superior performance of the ZMG system, achieving 85% MO removal under natural sunlight within 90 min, significantly surpassing the activity of both the individual components and binary composite. This enhanced activity is fundamentally due to an optimized synergistic relationship and an interfacial mechanism that ensures highly efficient charge-carrier separation. Under laboratory UV irradiation, the photocatalytic activity demonstrated excellent kinetics, achieving complete MO removal within 60 min and yielding the highest rate constant (κ = 0.070 min–1). Furthermore, the ZMG maintained excellent structural stability, with removal efficiency exceeding 96% after four consecutive reuse cycles. These findings validate the ZMG as a kinetically robust, sustainable, and highly effective candidate for practical wastewater remediation applications.