Structurally stable Ag/Ag2O@MOF-808 photocatalysts for efficient photodegradation of high-concentration Rhodamine B

The development of stable and efficient MOF-based photocatalysts is essential for the treatment of high-strength dye wastewater. In this study, Ag/Ag₂O@MOF-808 surface heterojunction photocatalysts were synthesized by a low-temperature impregnation calcination method. Comprehensive structural analyses (XRD, FT-IR, SEM, TEM, BET, H₂-TPR, XPS) confirmed successful silver loading without damaging the MOF-808 framework. By adjusting the calcination temperature, both Ag⁰ and Ag₂O were introduced to form surface heterojunctions with MOF-808. UV–vis DRS and valence band XPS showed that Ag₂O reduced the band gap and valence band position, improving light absorption and charge separation. The optimized catalyst (10 wt% Ag, 150 °C) achieved 98.1 % degradation of Rhodamine B (25 mg/L) under UV light within 60 min and maintained 88.8 % efficiency (within 180 min) at 100 mg/L. The catalyst exhibited excellent reusability with 0.417 % Ag⁺ leaching and over 73 % activity retention after four cycles. Radical scavenging experiments identified superoxide radicals as the dominant reactive species. The enhanced performance is attributed to the synergistic effect of Ag₂O as the active phase, Ag⁰ as a conductive bridge, and MOF-808 as a stable support. This work offers a controllable, oxidant-free strategy for efficient photocatalytic degradation of hazardous dyes in wastewater.