In situ fabrication of LDH-coated ZIF-9 nanocomposites for efficient PMS activation toward enhanced catalytic degradation of organic water contaminants

In this study, a series of novel nanocomposites were synthesized by growth of layered double hydroxides (LDH) surrounding of zeolitic imidazolate framework-9 (ZIF-9) core to form hierarchical structures with enhanced catalytic performance for water purification. The synthesized composites were designed as S₁₀, S₂₀, S₃₀, S₄₀, and S₅₀, based on the LDH content, which are systematically characterized and employed for the activation of peroxymonosulfate (PMS) for MB degradation. Catalytic performance demonstrated that while PMS alone exhibited negligible MB degradation (~ 22%), the addition of nanocomposites significantly enhanced the degradation efficiency to above 97%, notably with S₄₀ and S₅₀ samples in less than 30 min. Increasing the LDH content provides more available active sites, thereby accelerating PMS activation and dye degradation. Optimization experiments illustrate 5 mg of S₄₀ and 10 mg of PMS achieved the highest efficiency. Radical quenching experiments were also conducted to confirm that sulfate radicals (SO₄•⁻) played a more critical role than hydroxyl radicals (•OH) in the degradation process. This work highlights the potential of LDH/ZIF-9-based nanocomposites as efficient and stable catalysts for the degradation of organic dye pollutants, providing a promising approach for advanced wastewater treatment technologies.