Direct synthesis of platinum nanodots in ZIF-8/Fe₃O₄ core-shell hybrid nanoparticles

A novel method was developed for synthesizing platinum nanodots inside zeolitic imidazolate framework nanostructures without using additional reducing agents. Fe₃O₄ magnetic nanoparticle clusters (MNCs) were synthesized and coated with ZIF-8 (ZIF) shells via a hydrothermal reaction. Upon addition of ZIF/MNC hybrid nanoparticles into a platinum precursor (K₂PtCl₄) solution, platinum ions were reduced to metallic platinum nanodots by the 2-methyl imidazolate groups. The resulting platinum nanodots were ∼2 nm in diameter and uniformly distributed in the pores of the ZIF layer. The catalytic activity of the platinum nanodots was examined by using Pt/ZIF/MNCs for the reduction of 4-nitrophenol. The resulting high catalytic activity was attributed to the high surface area of the platinum nanodots and the absence of capping layers. Furthermore, the hybrid nanoparticles were recovered using a permanent magnet and were found to maintain their catalytic activity after multiple cycles.