Modulation of the electronic structure of Fe/Co 2D-MOFs by amination for promotion of 1O2 generation through hydrogen bonding with H2O2: the hitherto overlooked role of ligands

Abstract

Singlet oxygen (¹O₂) generation has attracted attention for the selective degradation of contaminants in the Fenton-like reaction. However, it is still a challenge to improve the catalytic activity for ¹O₂ generation via the H₂O₂-based Fenton-like reaction because of the symmetry structure of H₂O₂. Metal-organic frameworks (MOFs) are usually reported as catalysts in the Fenton-like reaction with metal atoms as the active sites. Nevertheless, the contribution of the ligand to the catalytic activity is always overlooked. Herein, two-dimensional (2D) MOFs (Fe/Co as the metal node, terephthalic acid/amino-terephthalic acid as the ligand) were synthesized as catalysts to activate H₂O₂, in which the amino-terephthalic acid displays catalytic activity to activate H₂O₂ for ¹O₂ generation under neutral and alkaline conditions as firstly reported. The experimental results indicated that an O-H bond in H₂O₂ was broken at the catalyst surface instead of the conventional O-O bond. Moreover, density functional theory (DFT) calculation further illustrated that a hydrogen bonding (NꞏꞏꞏH) formation between -NH₂ and H₂O₂ affected the electronic configuration of the adjacent C, resulting in the electron transfer accelerated and the catalytic activity improved for the ¹O₂ generation. The contribution of ¹O₂ reached about 93 %. The degradation pathway for methylene blue (MB) was proposed according to the mass spectrometry and DFT calculation, following a non-radical pathway with the majority of intermediates being non-toxic. This study supplied a strategy for the catalyst synthesis and ¹O₂ selective generation in the H₂O₂-based Fenton-like reaction.