A dual-functional adsorption-photocatalysis system driven by interfacial charge dynamics in a type-II 3D/2D CdIn2S4/nickel metal–organic layer heterojunction for environmental purification and water splitting

The efficient removal of pollutants and solar-driven hydrogen production are crucial for advancing a green economy, yet their practical implementation remains challenging. In this study, we shortened the transport path of photogenerated charge carriers and increased the interfacial contact area by exfoliating 3D nickel metal–organic frameworks (Ni-MOFs) into 2D nickel metal–organic layers (Ni-MOLs). A 3D/2D CdIn₂S₄/Ni-MOLs (CIS/NM) type-II heterojunction was successfully constructed via a one-pot solvothermal method, in which 3D CdIn₂S₄ was grown in situ on 2D Ni-MOLs. This heterojunction demonstrated synergistic and efficient adsorption-photocatalytic degradation of methylene blue (MB) and photocatalytic hydrogen production. Adsorption tests revealed that 1.5 CIS/NM achieved a capacity of 38.2 mg g⁻¹ for MB (30 mg L⁻¹) within 240 min, following the Langmuir isotherm model and pseudo-second-order kinetics. Under optimized initial MB concentration and pH conditions (C₀ = 10 mg L⁻¹, pH = 11), the synergistic removal efficiency of 1.5 CIS/NM reached 99.9 %. Density functional theory (DFT) calculations and mechanistic studies confirmed the formation of a type-II heterojunction between CdIn₂S₄ and Ni-MOLs, with $•\mathrm{OH}$ and $•O_2^{–}$ identified as the dominant reactive radicals. Furthermore, 1.5 CIS/NM exhibited excellent photocatalytic hydrogen evolution performance, with a rate of 1247 μmol g⁻¹ h⁻¹ and an apparent quantum efficiency of 8.1 % at 400 nm. This study offers a straightforward synthesis strategy for achieving adsorption-degradation of pollutants and solar hydrogen production, providing new insights for the design of bifunctional photocatalysts.