Tuning Lewis acidity of iron-based metal-organic frameworks for enhanced catalytic ozonation

Lewis acid sites that originate from ligand missing defects inspire diverse important applications of metal-organic frameworks (MOFs), such as heterogeneous catalysis. However, the facile regulation of Lewis acidity that promises good properties remains a challenge. Herein, we report a simple strategy to tune the Lewis acidity of iron-based MOFs. By substituting Fe centers with Ce atoms in the node (a.k.a., Ce doping), the catalytic ozonation performance of developed iron-based MOFs was highly improved. We found that both the total Lewis acidity and the salicylic acid (SA) degradation rate of Ce-doping MIL-88A(Fe) linearly correlated to the suitable Ce substitution ratio. Notably, the degradation rate and TOC removal of MIL-88A(Fe0.80Ce0.20) was about 3 and 2 times higher than those of parent MIL-88A(Fe), respectively. Reactive oxygen species (ROS), including surface adsorbed hydroxyl radicals (center dot OHads), superoxide radicals (center dot O-2(-)), and singlet oxygen (O-1(2)) were responsible for SA destruction. MIL-88A(Fe0.80Ce0.20) with enlarged Lewis acidity substantially facilitated the generation of center dot OH ads and O-1(2), leading to a more efficient SA degradation and mineralization. Moreover, Ce doping engineering also ameliorated the catalytic performances of MIL-53(Fe) and MIL-101(Fe), indicating that the tuning strategy we proposed is accessible and universal. This work may provide deep insights into highly efficient MOFs explorations for water purification.

Automated summary

Ce doping can significantly enhance the catalytic performance of iron-based MOFs, with total Lewis acidity and salicylic acid (SA) degradation rate linearly correlated to Ce substitution ratio. MIL-88A(Fe0.80Ce0.20) showed about 3 times higher degradation rate and 2 times higher TOC removal compared to the parent MIL-88A(Fe).