Overcoming the pH limitation of Fenton-like reactions and improving H2O2 utilization: synergistic dual Lewis acid sites and local acidic microenvironments.

Fenton-like technologies, as the most cost-effective method for degrading refractory organic compounds in wastewater, face inefficient H2O2 utilization (typically <35%) and a narrow operational pH range (pH < 4) critical bottleneck. To date, few studies have addressed both limitations simultaneously. Here, we report that dual Lewis acid and acidic microenvironments work synergistically to overcome these challenges cost-effectively. The efficient degradation of refractory organic pollutants was broadened to pH 3-9 in the carboxyl-functionalized montmorillonite-supported iron-boron dual Lewis acid catalyst (MMT-Fe-B-A)/H2O2 system, resulting in H2O2 utilization that is 6.1 times greater than Fe2+/H2O2 system. Experimental results and DFT simulations demonstrate that the carboxyl groups enhance the adsorption of reactants while providing H⁺ to create an acidic microenvironment, which accelerates Fe(II) regeneration. Moreover, the Fe-B dual Lewis acid sites facilitate the homolytic cleavage of H2O2, enhancing •OH generation rate at the catalytic interface and enabling the rapid degradation of toxic coupled by-products on the catalyst surface. Furthermore, while Lewis acid sites (Fe/B) are prone to OH⁻ adsorption-which can disrupt the acidic microenvironment-modulating the B/Fe ratio can balance Lewis acid sites and the acidic microenvironment. Owing to this "trade-off" effect, the decontamination efficiency for actual wastewater of the optimized system outperforms Fe2+/H2O2 system: SMZ removal and H2O2 utilization are 1.7 and 2.9 times greater, respectively, and TOC removal increases by 20%. Moreover, the estimated operating cost is reduced to 43.5% of the conventional system. This study offers a novel strategy for simultaneously expanding the pH applicability and efficiency of Fenton-like oxidation.