###### Abstract  
Carbon-red mud foam/paraffin hybrid materials were prepared and studied for their thermal energy storage and electromagnetic interference (EMI) shielding properties. The host matrices were prepared utilizing the polymeric foam replication method, with a polyurethane sponge as a template, resin as a carbon source, and red mud as a filler. The paraffins, n-octadecane (OD) and the commercial RT18 HC, were used as organic encapsulant phase change materials (PCMs) into the open pore structure of the foams. The foams' morphological and structural study revealed a highly porous structure (bulk density, apparent porosity P > 65%), which exhibits elliptical and spherical pores, sized from 50 up to 500 \(\mu\)m, and cell walls composed of partially graphitized carbon and various oxide phases. The hybrid foams showed a remarkable encapsulation efficiency as shape stabilizers for paraffins: 48.8% (OD), 37.8% (RT18 HC), while their melting enthalpies (\(\Delta\)H\({}_{\text{m}}\)) were found to be 126.9 \(\mathrm{J/g}\) and 115.5 \(\mathrm{J/g}\), respectively. The investigated hybrids showed efficient electromagnetic shielding performance in frequency range of 3.5-9.0 GHz reaching the entry-level value of -20 dB required for commercial applications, when filled with PCMs. Their excellent thermal and EMI shielding performance places the as-prepared samples as promising candidates for use in thermal management and EMI shielding of electronic devices as well. carbon foams; thermal energy storage; red mud; porosity; EMI shielding; organic PCMs 202 fatty acids, whereas the inorganic ones are usually salt hydrates. The eutectics are mixtures of two or more organic and/or inorganic PCMs, whose melting temperature covers some specific applications [13]. Among these materials, organic PCMs have several assets when compared to the other ones (inorganic, eutectics), such as the absence of subcooling effects, non-toxic nature, great stability upon cycling, and transformation without phase separation [14, 15, 16]. However, it should be noted that paraffins are quite flammable and exhibit low thermal conductivity, which combined with high volume variation during the phase transition and high leakage in the melting state could cause serious failures when utilized in thermal systems [17]. The most expedient method to prevent paraffin leakage during solid-liquid phase transition, and to reduce down the corrosion level of structural materials, is the use of a shape stabilizer (ss) supporting matrix, which encapsulates the PCM that allows it to sustain its molten form stationary at elevated temperatures [7, 18]. One promising route to enhance the thermal conductivity of the final hybrid product (building component + PCM + ss) is the dispersion of high thermal conductivity additives into the PCM, such as (i) expanded graphite, (ii) carbon nanotubes (CNTs) or nanofibers, (iii) metal, and (iv) ceramic nanoparticles [19, 20, 21, 22]. One other way to achieve the desirable reinforcement of the hybrids is to select a highly conductive ss matrix, such as metal foams and/or ceramic porous/foam structures [23, 24, 25]. In order to find an ideal combination of materials, a large number of porous matrices have been investigated so far as thermally conductive as candidates for PCMs, including activated carbons and other carbon-based porous nanomaterials, zeolites, silicate mesoporous materials, porous/foams ceramics, polymers, metal-organic frameworks, metallic foams, and other various types of composites, i.e., the supporting materials are more than one [26, 24, 27, 28]. Carbon-based porous materials are considered as shape stabilizers for PCMs, due to their higher thermal conductivities (up to 2.1 W/(m\(\cdot\)K)) [29] when compared to the polymers (<0.05 W/(m\(\cdot\)K) or ceramic analogues (\(\sim\)0.1 W/(m\(\cdot\)K).