Eco-friendly and cost-effective synthesis of hierarchical porous HKUST-1 from thin waste electric cables for enhanced cationic dye removal

Abstract

HKUST-1, as a type of metal-organic framework (MOF), has attracted significant interest for various applications. However, its use for adsorption applications is hindered by its microporous structure, which negatively impacts the diffusion and mass transfer of large particles (> 2 nm). Concurrently, waste electric cables from discarded vehicles and electronic equipment pose significant environmental challenges. To address these issues, we developed a novel recycling method using copper hydroxide recovered from waste-thin electric cables as the metal source for synthesizing hierarchical porous HKUST-1 (W) using a green approach at a low temperature. The resulting HKUST-1 (W) exhibited interesting properties compared to the typical HKUST-1 (C) synthesized from commercial precursors, showing a microporous-mesoporous structure with enhanced molecular mass transport, while HKUST-1 (C) exhibited only micropores. Moreover, the waste-derived HKUST-1 (W) formed interconnected small particles with enhanced methylene blue (MB) removal properties compared to HKUST-1 (C), mainly due to its hierarchical porous structure facilitating easy mass transfer of MB. To evaluate the industrial potential of our adsorbent, we conducted a fixed-bed adsorption column (FBAC) experiment, which showed that HKUST-1 (W) achieved a high removal efficiency of 99 %, confirming its effectiveness as a dye adsorbent in both batch experiments and a FBAC. This approach opens new perspectives in applying upcycled waste-based materials in synthesizing hierarchical porous MOFs.