A Novel 2-Chloro-4-Nitrophenol Photoelectrochemical Sensor Based on MWCNTs@MIL-68(In) Derivatives and In ₂ O ₃ Composite Films

2-Chloro-4-nitrophenol (2C4NP) is a traditional organic pollutant whose toxicity constitutes a significant threat to both human health and environmental safety. Therefore, developing a method for the accurate detection of 2C4NP in natural environments is imperative. Consequently, we develop a photoelectrochemical sensing platform based on MWCNTs@In 2 S 3 /In 2 O 3 /GCE in this work. During the construction process, it is discovered that the introduction of MWCNTs accelerated the electron transport rate, which improved the separation efficiency of photogenerated electron–hole pairs in In 2 S 3 . Meanwhile, the MWCNTs@In 2 S 3 /In 2 O 3 composite materials formed by MWCNTs@In 2 S 3 and In 2 O 3 not only exhibit an S-scheme heterojunction but also preserve the intrinsic advantages of MOFs-derived materials. This synergistic structure endows the composite materials with excellent optoelectronic performance and adsorption capability. Thus, the constructed photoelectrochemical sensing platform demonstrates promising potential for detecting 2C4NP, with a linear detection range from 3 nM to 5 μM. However, compared to some existing platforms, its detection range remains relatively narrow, which may represent an area for future improvement.