Nanoscale porous metal–organic frameworks and related materials have received considerable attention in recent years due to their widespread applications. However, the effective synthesis of magnetic core–shell MOFs still remains a significant challenge. In this article, a Fe₃O₄@ZIF-8 core–shell nanostructure with unique morphology, a large specific surface area, excellent thermal stability, and superparamagnetic properties is reported. Additionally, instead of using organic surfactants, a surfactant-free and facile synthesis route is successfully developed. The ZIF-8 shell thickness can be precisely controlled by altering the number of growth cycles. Fe₃O₄@ZIF-8 shows good adsorption properties for MB, with maximum adsorption capacity of 20.2 mg g⁻¹.

Fine-grain induced ultrahigh energy storage density and fast discharge speed in novel Bi _0.5 K _0.5 TiO ₃ –Ba(Mg _1/3 Nb _2/3 )O ₃ ceramics via a hot-pressing strategy.