In Situ Constructed Magnetic Core‐Shell Hydrogen‐Bonded Organic Framework‐on‐Metal–Organic Framework Structure: an Efficient Catalyst for Peroxymonosulfate Activation

Abstract Zeolite imidazole‐based framework (ZIF‐67), a notable class of metal–organic frameworks (MOFs), shows promise in activating peroxymonosulfate (PMS) for pollutant degradation due to its uniformly distributed cobalt ions. However, its nanoparticle form and the elution of cobalt ions during use cause challenges in recycling and the risk of secondary pollution. In this study, a magnetic core‐shell hydrogen‐bonded organic framework (HOF) on the MOF (HOF‐on‐Fe 3 O 4 /ZIF‐67) is successfully prepared. The porous HOF shell not only protects the active sites and mitigates cobalt ion leaching but also reduces mass transfer limitations, ensuring sustained catalytic performance. The magnetic Fe 3 O 4 core enhances electron transfer between cobalt ions, boosts catalytic efficiency, and facilitates easy separation and recycling. This core‐shell structure effectively activates PMS, achieving 100% removal of Rhodamine B, a model wastewater dye, within 10 min (Rh B = 50 mg L −1 , HFZ = 150 mg L −1 , PMS = 1.5 m m , pH = 7, room temperature). Furthermore, under the protection of the HOF shell, cobalt ion leaching is minimized to a negligible value (0.14 mg L −1 ) after 5 cycles of use. The research provides fresh perspectives into the development of core‐shell composite materials with improved performance and recyclability in wastewater treatment.