Engineering Interfacial Electronic Synergy in Metal–Organic Framework-Derived Ni ₂ P-Anchored NiCo ₂ S ₄ Microflowers for Nanomolar Detection and Catalytic Hydrogenation of 4-Nitrophenol

A dual-functional Ni 2 P–NiCo 2 S 4 heterostructure was fabricated by engineering hierarchical NiCo 2 S 4 microflowers on a metal–organic framework (MOF)-derived porous Ni 2 P scaffold using a facile hydrothermal method. Structural and compositional investigations using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and electron microscopy (Field emission scanning electron microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM)) confirm the formation of a well-integrated heterointerface between Ni 2 P and NiCo 2 S 4 . The hierarchical structure provides numerous active sites and enhances efficient interfacial charge transfer. Cyclic voltammetry and differential pulse voltammetry experiments demonstrate that the modified electrode displays a highly sensitive response to 4-nitrophenol (4-NP). Quantitative detection is achieved across a broad concentration range of 0.005–100 μM, with a detection limit of 1.1 nM in 0.1 M KNO 3, and exhibits exceptional selectivity against common interfering substances. The improved sensing capability is due to robust electronic interactions between Ni 2 P and NiCo 2 S 4, which promote rapid electron transfer and catalytic activation of 4-NP. The Ni 2 P–NiCo 2 S 4 heterostructure serves as an effective catalyst for the NaBH 4 -assisted reduction of 4-NP, achieving a fast conversion to 4-aminophenol within 6 min at ambient temperature. The integrated MOF-derived phosphide frameworks and hierarchical sulfide microstructures offer a viable approach to creating multifunctional materials for environmental sensing and catalytic remediation.