Synthesis of nickel sulphide nanosheets using imidazolium-based chloronickellate ionic liquids as precursors/templates for sunlight-assisted degradation of organic dyes†

In the current work, two new bifunctional Brønsted–Lewis acidic chloronickellate ionic liquid systems, 1a and 1b ([RSIM]_x[NiCl_y], where R = C₂H₅ and CH₃, x = 2, y = 2, 3, 4 or 5), were developed by incorporating two –SO₃H groups into the imidazolium cation. These chloronickellate ionic liquids (ILs) were then utilized as precursors/templates in the synthesis of nickel sulphide nanosheets (2a and 2b) using a simple grinding method. The synthesized nanosheets were characterized using PXRD, FT-IR, RAMAN, TEM, SEM-EDX, XPS, BET and UV-visible analysis. The photocatalytic activities of these nanosheets were then explored in the degradation of organic dyes (methylene blue, methyl orange, crystal violet and malachite green) and their mixtures in the presence of sunlight. The nanosheet 2a exhibited excellent degradation efficiency of 98.38% for methylene blue at pH = 7. The recyclability study established the stability and feasibility of multiple utilizations of the photocatalyst, supporting its potential implementation in water remediation.