Sustainable composite insulator for thermal, moisture, and electromagnetic shielding using recycled waste polymers/bimetallic MOF-grown porous carbon

This study introduces a sustainable and cost-efficient approach for developing multifunctional composite insulators designed for electromagnetic wave (EMW) shielding in the X-band (8.2–12.4 GHz) and thermal insulation. The proposed materials target applications as exterior building coatings with combined thermal, moisture-resistant, and electromagnetic protective capabilities. The composites were fabricated using recycled polystyrene (PS) as the polymer matrix and a copper–nickel metal–organic framework (Cu-Ni MOF) grown in situ on porous carbon (POC) derived from waste polyethylene terephthalate (PET). Sample preparation was carried out via the solution-casting technique using the green solvent of D-Limonene, with varying filler loadings of 2, 5, 8, and 15 wt%. The highest shielding effectiveness was obtained approximately 42 dB for the composite containing15 wt% Cu-Ni-MOF at only 2 mm thickness, corresponding to 99.94% attenuation of incident EMW radiation. For this sample, thermal conductivity was measured 0.132 W·m− 1·K− 1 at 30 °C which is 27.5% lower than that of pure polystyrene (0.182 W. m⁻¹. K⁻¹)—demonstrating enhanced thermal insulation. These findings underline the potential of PS/Cu-Ni MOF/POC composites as environmentally friendly, versatile materials for energy-efficient and EM-shielding architectural applications.