Architectural modulation of binary metal-organic frameworks upcycled from waste polyethylene terephthalate for high-performance supercapacitors.

The widespread and uncontrolled disposal of polyethylene terephthalate (PET) plastics poses a significant environmental challenge. In this study, we propose a sustainable upcycling strategy to convert waste PET into high-value bimetallic nickel/cobalt-1,4-benzenedicarboxylate metal-organic frameworks (NiCo-BDC MOFs) via a one-pot solvothermal method. By tuning the Ni/Co precursor ratio, the morphology of the resulting NiCo-BDC transitions controllably from stacked nanowires to nanorods, forming a hybrid crystalline-amorphous architecture with a large specific surface area and well-developed hierarchical porosity. Among the synthesized materials, Ni_1.5Co_0.5-BDC exhibits outstanding electrochemical performance, delivering a specific capacitance of 949 F g^-1 at 2 A g^-1 and maintaining 820 F g^-1 at 20 A g^-1. When assembled into an asymmetric supercapacitor with biomass-derived nano‑carbon, the device achieves an energy density of 22 Wh kg^-1 at a power density of 1613 W kg^-1, with 83 % capacitance retention over 5000 cycles at 10 A g^-1. Notably, this upcycling approach demonstrates broad adaptability to various types of PET waste, offering a versatile platform that integrates plastic valorization with the development of high-performance electrode materials for next-generation energy storage systems.