Covalent metal–organic porous polymer on ZIF-67 realize anti-UV and highly stressed flame retardant epoxy composites

Abstract

Ferrocene (Fc) and metal–organic frameworks (MOFs) are established as effective functional additives in polymer composites, known for their synergistic effects. However, simple physical mixing does not fully harness their potential. To optimize their performance, we developed a method to graft ferrocene onto zeolitic imidazolate frameworks (ZIFs) via a Schiff base structure, followed by constructing a ferrocene-based covalent metal–organic porous polymer (CMOPP) network using Friedel-Crafts alkylation. This approach addresses the mesoporous structure limitation in ZIFs. During this process, the imidazole ligands are etched, yielding a yolk-shell structured, hierarchically nanoporous flame retardant. The synergy between ferrocene and ZIF significantly enhances the UV protection of epoxy resin, with a 99.1% reduction in UV transmittance. Additionally, ferrocene improves the filler-matrix compatibility, increasing tensile strength by 15.1%. This combination of flame-retardant elements and the porous structure’s adsorption capacity imparts exceptional flame retardancy and smoke suppression to the epoxy resin, evidenced by a Limiting Oxygen Index of 28.3% and a V-0 rating in the UL-94 test. Notable reductions include 56.5% in peak heat release rate, 55.1% in peak smoke production rate, and 71.6% in peak carbon monoxide production. This work introduces a novel strategy for designing high-performance multifunctional flame retardants.