Facile and scalable synthesis of Fe-based metal organic frameworks for highly efficient photo-Fenton degradation of organic contaminants

Fe-based metal organic frameworks (Fe-MOFs) being a newly developed photo-Fenton catalyst, have gained ever-increasing attention for environmental remediation, but have been limited by high synthesis cost (high energy-consumption and low yield). In this work, economical and scalable synthesis of Fe-BDC₁ (BDC denotes as terephthalic acid) was achieved via facile stirring under ambient condition, and its adsorptive, photocatalytic, Fenton-like and photo-Fenton performances were comprehensively explored against contaminants removal. In comparison, synthesized Fe-BDC₂ with the common solvothermal method, the yield of Fe-BDC₁ increased 3.4 times. Also, its adsorption capacity towards Rhodamine B (Rh. B) increased about 5.85 times. Moreover, the significantly improved degradation of Rh. B was observed in the Fenton-like and photo-Fenton systems with the increased reaction rate constants up to 4.90 and 2.33 times, respectively. This enhanced catalytic performance of Fe-BDC₁ was mainly attributed to the enlarged specific surface area (SSA) and favorable electron separation and migration, resulting into the accelerated ≡Fe(II)/≡Fe(III) cycle and increased yield of reactive oxidative species (ROSs). Additionally, the unique light-induced adsorption enhancement further strengthened the contaminants removal. Fe-BDC₁ as photo-Fenton catalyst was found superior over conventional catalysts in terms of advantages including: low dose requirement of catalysts (decrease in an order of magnitude) and H₂O₂, wide pH working range (3.0–9.0), excellent reusability and stability, universal removal behavior against all organic pollutants, and remarkable synergism between photocatalysis and Fenton-like process with synergistic factor of 77.23%. Moreover, the Fe coordinative unsaturated sites (Fe CUSs) and ·OH were determined as the active sites and the main ROSs, respectively, responsible for highly efficient pollutant degradation. This work gives a feasible solution for the preparation of Fe-MOFs with low synthesis cost and high yield, paving ways for their practical mass application in heterogeneous photo-Fenton oxidation.