Influence of cation doping (Li⁺, Na⁺, K⁺) on photocatalytic activity of MIL-53(Fe)

The work highlights the influence of cation doping on photocatalytic activity of MIL-53(Fe) in artificial light. The effect of intrinsic factors, viz. band-gap energy, electron conductivity and surface area, influencing photocatalysis was studied in detail w.r.t. the degradation of brilliant green dye both in the presence and in the absence of H₂O₂ as an electron scavenger. Reduction in band gap after cation doping was observed for Li⁺ (1.81 eV), Na⁺ (1.875 eV) and K⁺ (1.89 eV) when compared with the parent MIL-53(Fe) (1.95 eV). However, the photoactivity of the synthesized materials was in the following progression: MIL-53(Fe)(81.6%) >#Thin Space#Li-MIL-53(Fe)(27.6%) >#Thin Space#Na-MIL-53(Fe)(25.77%) >#Thin Space#K-MIL-53(Fe) (24.18%). Effect of structural distortions in the octahedral backbone of MIL-53(Fe) due to cation doping was inferred as the plausible reason behind such behavior. The degree of electron delocalization and specific surface areas were found to be in the following progression: Na-MIL-53(Fe) (very low, 7.72 m² g⁻¹) < K-MIL-53(Fe) (low, 28.38 m² g⁻¹) < Li-MIL-53(Fe) (moderate, 42.14 m² g⁻¹) < MIL-53(Fe) (high, 51.71 m² g⁻¹), indicating that the intrinsic material properties have combinatorial influence on photocatalytic activity.