To develop highly recyclable and efficient catalytic materials is

pivotal for sustainable treatment of wastewater. Herein, gold

nanoparticle (AuNP) films immobilized on a lithium-ion battery separator

were fabricated via a facile vacuum filtration method, demonstrating

exceptional catalytic activity and recyclability for the conversion of

nitrophenols and azo dyes. This porous separator architecture provided

abundant anchoring sites for AuNPs, enabling rapid substrate diffusion

and minimizing nanoparticle aggregation. Under optimized conditions

(1000?mM NaBH?), the AuNP film achieved complete catalytic conversion of

2-nitrophenol to 2-aminophenol within 36?min. Remarkably, the film

retained >?98?% efficiency over 8 consecutive cycles, underscoring

its robust reusability. Two-dimensional correlation spectroscopy

(2D-COS) elucidated the reaction mechanism, revealing that

nitrophenolate ions (415?nm) dominated the conversion kinetics, followed

by the slower formation of aminophenol (295?nm). The AuNP film also

exhibited versatility, converting 4-nitrophenol (32?min), methylene blue

(8?min), and methyl orange (15?min) efficiently. The synergy between

the separator’s hierarchical porosity and AuNP’s catalytic activity

facilitated electron transfer and active hydrogen generation. This work

presents a scalable, low-cost strategy for industrial pollutant

remediation, leveraging recyclable AuNP films and advanced spectroscopic

analysis to bridge material design and environmental application.