## 3 EMA and Flame-Retardant Dual-Functional MOF Composites
### Co-Mof  
ZIFs are a special family of crystalline materials that are a subclass of MOFs. A typical example of one of these is ZIF-67, which has imidazole as the bridging ligand and Co ions as the core metal. Because of its strong electrical conductivity and large number of surface active sites, ZIF-67 has attracted a lot of interest as a precursor for EMA, catalysis, and sensing applications [82; 83; 84]. [PERSON] et al. [85] discovered that when melamine serves as the structural matrix, ZIF-67 particles can uniformly grow on the foam surface via hydroxyl radicals. After calcination, they obtained a 3D hybrid foam, MZT, with EMA functionality (Figure 3a). As shown in Figure 3b,c, the hybrid foam achieved a RL\({}_{\text{min}}\) of \(-59.82\) dB at a thickness of 2.3 mm and an EAB of 5.64 GHz at a relatively thin thickness of 2.1 mm. When the hybrid foam was placedon a heating platform at 70 \({}^{\circ}\)C, the surface temperatures recorded over 5 to 30 min were 18.3, 18.5, 18.9, 19.4, 19.5, and 19.9 \({}^{\circ}\)C, respectively, demonstrating its excellent infrared stealth and thermal insulation properties (Figure 3d). [PERSON] et al. [86] designed a porous composite material consisting of Co-MOF-loaded CNTs and expanded graphite (Co/CNTs/EG) (Figure 4a). At an ultra-low filler loading of 3 wt.% and an ultra-thin thickness of 1.4 mm, the Co/CNTs/EG composite achieved a RL\({}_{\text{min}}\) of \(-67.2\) dB and an EAB of 5.1 GHz (Figure 4b,c). Figure 4(d\({}_{1}\),d\({}_{2}\)) shows that when the composite was blended into the EP matrix and subjected to a 20 s alcohol lamp test (-500 \({}^{\circ}\)C), the pure EP was ignited, whereas the Co/CNTs/EG/EP sample held its shape and showed no apparent flames, smoke, or dripping. Figure 4(e\({}_{1}\)-e\({}_{3}\)) shows infrared thermal pictures of Co/CNTs/EG taken over a period of 3-9 min. These pictures demonstrate that the Co/CNTs/EG composite effectively isolates heat and blocks infrared radiation, showing its suitability for infrared stealth applications. Figure 4(e\({}_{4}\)) compares the Co/CNTs/EG composite's infrared shielding efficacy to two other materials (commercial polyurethane foam (PU) and nickel foam (NF)), exhibiting that the Co/CNTs/EG composite  
Figure 3: MZT hybrid foam: (**a**) schematic diagram of the synthesis process, (**b**) 3D RL diagram, (**c**) RL-f curve, (**d**) thermal infrared image at 70 \({}^{\circ}\)C (reprinted with permission from [85] © 2020 American Chemical Society). Figure 2: Fe/C/CF: (**a**) schematic diagram of synthesis process, (**b**) 3D RL diagram, (**c**) RL–f curve, (**d**) thermal infrared image of hand, (**e**) infrared stealth diagram, and (**f**) thermal infrared image at 120 \({}^{\circ}\)C (reprinted with permission from [81] © 2023 Elsevier). has considerably greater thermal insulation. This highlights its immense application potential in thermal insulation and infrared stealth technologies. 3D printing technology has introduced new opportunities for the design and fabrication of multifunctional materials, enabling the creation of complex shapes with unprecedented possibilities. [PERSON] et al. [87] selected a polarity-induced rigid-flexible EP/multifluorination/siloxane network as a supporting material and prepared multidimensional nanofillers CoMXene (CoM) and CoNiCNT (CoNiC) through an in situ growth and pyrolysis process of ZIF-67. Stable CoM@CoNiC-F links were created using C-F\(\cdots\pi\) interactions. These inks were utilized to 3D print high-resolution and complex-shaped CoM@CoNiC-F nanocomposites via direct-ink-writing technology (Figure 5a). Additionally, the 3D-printed objects exhibited reliable photothermal-induced shape memory properties, facilitating the fabrication of 4D-printed structures with dynamic shape evolution behavior. The composites demonstrated excellent EMA performance, with a RL\({}_{\text{min}}\) of \(-64.78\) dB and an EAB of 4.6 GHz (Figure 5b).