Development of an In2S3/metal organic framework heterostructure coupled with an ionic liquid as a potential composite for environmental remediation

• The IMI3 composite exhibits enhanced crystallinity, as evidenced by a reduced I D /I G ratio. • The IMI3 composite exhibits visible light absorption attributed to its narrow band gap. • The IMI3 composite demonstrates successful creation of a S-scheme heterojunction with enhanced separation of charged carriers. In this research, a novel composite material was developed, comprising In₂S₃ (indium sulfide) and NH₂-MIL-125 (a metal-organic framework) modified with [BMIM]BF₄ (an ionic liquid/IL). This innovative composite material shows significant potential for environmental remediation. The introduction of NH₂-MIL-125/IL in In₂S₃ reduces the crystallite size of the In₂S₃/NH₂-MIL-125/IL nanocomposites, with the surface area increasing as the NH₂-MIL-125/IL content rises from 41.89 m²/g to 95.25 m²/g. The ability to control the tetragonal and cubic phases of β-In₂S₃ using ionic liquids represents a significant advancement in nanomaterial design. The calculated I D /I G ratios for 1 % In₂S₃/NH₂-MIL-125/IL, 3 % In₂S₃/NH₂-MIL-125/IL, and 5 % In₂S₃/NH₂-MIL-125/IL are 0.46, 0.46, and 0.14, respectively. The 5 % In₂S₃/NH₂-MIL-125/IL composite exhibits the lowest I D /I G ratio, indicating fewer defects and higher crystallinity due to its higher NH₂-MIL-125/IL loading. This improved crystallinity enhances the material's structural integrity. A new FTIR peak at 913 cm⁻¹ in the In₂S₃/NH₂-MIL-125/IL composite suggests chemical interactions between In₂S₃ and NH₂-MIL-125/IL. TEM images confirm the preservation of the pristine structures, with In₂S₃ forming nanosheets, NH₂-MIL-125 adopting hexagonal structures, and In₂S₃/NH₂-MIL-125/IL displaying a combined morphology. XPS, TEM, and EDX analyses support the successful formation of the In₂S₃/NH₂-MIL-125/IL heterostructures. The 5 % In₂S₃/NH₂-MIL-125/IL composite shows improved optical and photocatalytic properties, including a reduced band gap of 2.09 eV, a redshift in absorption, and reduced photoluminescence intensity, indicating lower charge recombination. Photocurrent tests revealed that 5 % In₂S₃/NH₂-MIL-125/IL had the highest photocurrent density (0.018 mA/cm²), and Mott-Schottky analysis indicated that it had the lowest flat band potential (-1.43 V), requiring less energy to initiate photocatalytic processes. The composite's photocatalytic performance was further enhanced by the formation of an S-scheme heterojunction, which facilitates electron migration and improved charge separation, making it promising for applications such as wastewater treatment.