Regulating N content to anchor Fe in Fe-MOFs: Obtaining multiple active sites as efficient photocatalysts

Abstract

BackgroundIn order to make Fe-MOFs more fully utilized sunlight, more metal active sites were required to activate the reactants. The design of the materials with structure exposing more active sites became one of the most critical factors to improve catalytic performance. MethodsA novel dual-ligand Fe-MOFs, with N-containing ligands for regulation of active sites, were synthesized with dielectric barrier discharge (DBD) plasma for the first time. 1,3,5-benzenetricarboxylicacid (H3BTC) was used as organic ligands, while 2-methylimidazole (2MI) was added together for regulation of active sites. Significant findingsN-Fe-MOFs-2 with FeCl3•6H2O and ligands molar ratio of 1:2 exhibited the best photocatalytic performance. N-Fe-MOFs-2 had higher N content, which was conductive to anchoring Fe and provided more sites for the anchoring of metallic Fe. N-Fe-MOFs-2 showed larger specific surface area (70.18 m2/g) and relative smaller particle size (55 nm), and exhibited narrow band gap (2.55 eV), which was beneficial to the transportation of photonics. N-Fe-MOFs-2 exhibited lower PL intensity, which meant the lower photo-generated electron-hole recombination rate and showed higher photocatalytic performance with degradation rate of 97% in 48 min for methyl orange (20 mg/L) under visible light. EPR proved that superoxide radical anions (•O2−) and oxhydryl (•OH) radicals played important roles during photocatalytic. Radical capture experiments confirmed that holes (h+) and electron (e−) were major active species for the photodegradation of MO dye, •OH and •O2− radicals played minor role in the photo-decomposition of MO. What's more, the possible photocatalytic mechanism of N-Fe-MOFs was proposed, both degradation pathways and degradation intermediate products were confirmed via LC-MS.