Bimetallic FeNi-MOF@Al-foam metal composites for enhanced broadband noise reduction: sound absorption performance analysis and materials structural optimization.

Noise pollution significantly impacts human health and quality of life. This study developed FeNi-MOF@Al-FM composite materials for enhanced sound absorption and addressed limitations of traditional acoustic materials. FeNi-MOF@Al-FM composites were synthesized by loading FeNi-MOF onto aluminum foam metal (FM) substrates with various thicknesses (5-15 mm) and mass ratios (5-20%). Microscopic characterization confirmed the successful synthesis of hexagonal spindle-type FeNi-MOF structures. XRD analysis showed that nickel doping caused slight lattice changes while maintaining the crystal structure. FTIR identified characteristic functional groups, and XPS confirmed Fe-Ni co-doping with multiple nitrogen species. Acoustic testing revealed that sound absorption capacity increased with material thickness, with 15 mm composites performing best across all frequencies. At a fixed 5 mm thickness, increased FeNi-MOF loading significantly enhanced absorption, as 20% mass ratio composites achieved an absorption coefficient of 0.82 at 4000 Hz, representing a 3.7-fold improvement over unloaded samples. Absorption mechanisms were proposed: low-frequency resonance absorption (600 Hz) originating from microstructures between MOF and foam metal, and high-frequency porous absorption resulting from viscous/thermal dissipation within hierarchical pores. These findings establish structure-performance relationships for FeNi-MOF@Al-FM composites and demonstrate potential applications in noise control, architectural acoustics, and instrument vibration isolation.