Self-assembled monolithic β-FeOOH/copper foam catalysts for enhanced catalytic reduction of nitrogen-containing contaminants in continuous-flow systems

Abstract

Due to its relatively automated and straightforward operational process, continuous-flow catalysis has emerged as a promising technology for treating nitrogen-containing contaminants. However, achieving high activity and low flow resistance in packed-bed catalysts within continuous-flow systems remains a grand challenge. This study successfully constructed an integrated catalyst with a three-dimensional multi-level pore structure by self-assembling nano-flower-like β-FeOOH active components on a copper foam substrate. This catalyst can be easily integrated into a fixed-bed platform to build an efficient and stable continuous-flow catalytic system. The catalyst exhibited exceptional performance, achieving complete reduction of 4-nitrophenol within 49 s and maintaining over 98.2% catalytic efficiency after 10 consecutive cycles. It also demonstrated broad-spectrum activity, degrading various organic dyes such as methylene blue, Congo red, Rhodamine B, and methyl orange within 121 s. The substantial enhancement of catalytic activity is primarily attributed to the synergistic effects of three key factors: (1) efficient mass transfer enabled by the 3D hierarchical pore structure of the nano-flower-like β-FeOOH; (2) fully exposed active sites – Fe³⁺ on β-FeOOH catalyzes the hydrolysis of BH₄⁻ to generate active hydrogen species (H*); and (3) the sustainable Fe³⁺/Fe²⁺ redox cycle maintained by CF's excellent electron conductivity: CF transfers electrons to Fe²⁺ (generated from Fe³⁺ reduction during H* production) to regenerate Fe³⁺, ensuring continuous catalytic kinetics. This enhancement mechanism provides a new strategy for designing high-performance environmental catalytic materials. By integrating multiphase catalysis with flow chemistry technology, this study not only expands the conceptual framework for constructing environmental catalytic materials but also offers a more scalable, efficient, and environmentally compatible solution for wastewater treatment.