Axial g-C3N4 coordinated iron(III) phthalocyanine mediated ultra-efficient peroxymonosulfate activation for high-valent iron species generation

Herein, a new axial g-C3N4 coordinated iron(III) phthalocyanine (FeP/CN) was fabricated for peroxymonosulfate (PMS) activation. Around 100% degradation of acetaminophen (AP), 2,4-dichlorophenol (2,4-DP), sulfadiazine (SDZ), and methyl orange (MO) (30 mg L-1) were achieved within 20 min by adding 0.02 g L-1 FeP/CN5 (3.62 wt% Fe) and 0.2 mM PMS. High-valent iron-oxo species (FeIV=O) was demonstrated as the main reactive species, which mediated a two-electron transfer process with pollutants. Characterizations and computational analysis revealed that the axial g-C3N4 ligand provided Fe(III) coordination environments to generate FeIV=O species directly through PMS activation, and increased the reactivity of the FeIV=O species in pollutants oxidation due to the narrowed HOMO-LUMO gap. Besides, small displacement of Fe atom (0.23 Å) from the macrocycles plane due to the axial g-C3N4 ligand decreased the iron demetalization rate from 3.54% to 0.28% in the catalyst/PMS system. This work offered an excellent strategy to design high-efficiency catalysts for FeIV=O generation.