Construction of novel Cu-based bimetal polycrystal@carbon catalyst prepared from bimetal HKUST-1 type MOFs (MOF-199s) for ultrafast reduction of 4-nitrophenol via interfacial synergistic catalysis

The novel Cu-based bimetal polycrystal@carbon (C-HK(Cu/M)) composites derived from metal (Ni, Zn and Co) in-situ substituted Cu-based HKUST-1 were successfully fabricated by partial reduction strategy and employed for the reduction of 4-nitrophenol (4-NP). Systematic characterization demonstrated that Ni showed stronger orbital hybridization with Cu than Zn and Co, thereby significantly improving the catalytic properties of the C-HK(Cu/Ni) composite. The presence of Ni in HKUST-1 efficiently inhibited the reduction of adjacent Cu clusters, leading to the generation of unique polycrystal NiO/Cu/CuO nanohybrids (2.4–8.0 nm) with high dispersion (Cu exposure reaching 88.5%). While, the MOF ligands were catalyzed by doping Ni into the conductive and porous carbons, and finally engineered interfacial synergistic catalysis for enhancing the kinetics and stability for the reduction of 4-NP. The porous support accelerated 4-NP diffusion and adsorption in the composite, and as a consequence, the surrounding polycrystal nanohybrids on conductive carbon were responsible for producing hydrogen reducing species for 4-NP reduction. Therefore, C-HK(Cu/Ni) exhibited ultrafast kinetics and turnover frequency (TOF) for 4-NP reduction, which were up to 179 and 14 times higher than parent C-HK(Cu), surpassing the current state-of-the-art noble metal catalysts. Moreover, the activity of C-HK(Cu/Ni) was evaluated for six consecutive runs with minimal loss, demonstrating the high reusability and practicability of the catalyst on an industrial scale.