Magnetic Fe,Co-Nanocarbon Frameworks Derived from Fe-Doped Zeolitic Imidazolate Framework-67 as Highly Active Catalysts for 5-Hydroxymethylfurfural Oxidation.

Abstract

Zeolitic imidazolate frameworks (ZIFs) have recently emerged as promising precursors for the synthesis of heteroatom-doped nanocarbon materials. The chemical and structural features of these frameworks are influenced by the synthesis methodology, which directly affects their catalytic efficiency and stability. This study aims to investigate such frameworks by exploring a Co-ZIF structure doped with iron. Part of the Fe_xCo_y-ZIF (x = 0.05-0.15; y = 0.95-0.85) precursors is directly pyrolyzed to form Fe_xCo_y-NPC (NPC-nanoporous carbon), while another part is coated with a silica shell, followed by the pyrolysis of the Fe_xCo_y-ZIF@SiO₂ intermediates to produce Fe_xCo_y-NCF (NCF-nanocarbon framework). To elucidate their chemical, structural, and catalytic properties, the synthesized materials are comprehensively characterized and finally investigate in the base-free oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). The optimal catalyst (Fe_0.15Co_0.85-NCF) demonstrates complete conversion of HMF (>99.9%) to FDCA with a pretty high selectivity (82.4%) after 6 h reaction at 80 °C. The correlation of the catalytic features with the efficiency of the catalysts provides insight into the catalytic characteristics responsible for the highest HMF conversion and selectivity to FDCA. The stability and recyclability of the catalysts are also examined.