Metal‐Organic Framework Derived Multidimensional Carbon/Multifluorination Epoxy Nanocomposite with Electromagnetic Wave Absorption, Environmentally Adaptive, and Blue Energy Harvesting

Bimetallic metal−organic framework (MOF)‐derived multidimensional composites have garnered tremendous attention in electromagnetic wave absorption owing to their remarkable attenuation capacity. And the diversified application scenarios require microwaves absorption materials (MAMs) with robust environmentally adaptive, but efficiently integrating multifunctionality within single MAMs is extremely challenging. Herein, a multifunctional CoC@FeNiG‐F nanocomposite is fabricated by synergistic strategy of in situ growth, C–F···π interaction and microwave irradiation. The MAMs exhibit a strong reflection loss of −75.18 dB with 3.95 GHz effective absorption bandwidth benefited from magnetic–dielectric attenuation, impedance matching, and multiple‐reflection loss. Remarkably, it is first time to obtain the efficient MAMs accompanied with excellent mechanical (80.3 MPa), superamphiphobicity (153° and 151°), anticorrosion (45 d), and flame retardancy (V‐0 rating), which illustrate that the combination of CoC@FeNiG 3D‐skeleton and long‐chain perfluorinated epoxy remarkably improve robust multifunctionality and environmentally adaptive. In particular, the MAMs are assembled into liquid–solid triboelectric nanogenerator, and the output performance (19.7 V, 1.68 μA) and durability (10 000s) are obviously improved benefiting from the trap effect of carbonized MOF. Therefore, this work provides an efficient guideline for designing advanced MAMs with robust environmentally adaptive and sustainable energy harvesting performance in extreme environment application.


Introduction
The electromagnetic wave (EMW) pollution will inevitably arise with the prosperous evolution of wireless communications and integrated electronic devices. [1]onsequently, microwaves absorption materials (MAMs) with strong attenuation capacity, wide frequency, lightweight, and thin thickness are crucial to human health and military security. [2]Furthermore, MAMs will be applied to various complex and extreme environment in the future, which require the robust multifunctionality and environmentally adaptive to adapt to frontier and next-generation applications. [3]or instance, satisfactory superamphiphobicity and anticorrosion MAMs can be used in aerospace and naval ships/submarines for maintaining the corrosion resistance and stability.And MAMs with flame retardancy and robust mechanical performance is feasible to adapt to harsh hightemperature and flame environment and robust mechanical performance is feasible to adapt to harsh high-temperature and flame environment, which significantly improve the thermal stability and fire safety for industrial and military equipment.Moreover, MAMs with adjustable absorption capacity and blue energy harvesting are attractive strategy for sustainable power generation and effective EMW protection for wireless communications and portable electronics.
Nevertheless, the traditional EMW absorption strategy with single loss absorption mechanism hardly satisfies highperformance and multifunctional attenuation requirements. [4]p to now, many researches exhibited that the combination of magnetic particles and carbon materials have developed as effective strategy for improve the EMW absorption due to the synergetic electromagnetic losses and impedance matching. [5]in et al. obtained the flower-like Co/ZnO@CMWCNTs/ Ti 3 C 2 T x with minimum reflection loss (RL min ) is À46 dB and effective absorption bandwidth (EAB) is 4 GHz. [6]nfortunately, traditional magnetic nanoparticles (oxides, alloys, ferrites, etc.) tend to agglomeration due to magnetic dipoledipole attraction, and the reasonable structure regulation is still DOI: 10.1002/sstr.202300210Bimetallic metalÀorganic framework (MOF)-derived multidimensional composites have garnered tremendous attention in electromagnetic wave absorption owing to their remarkable attenuation capacity.And the diversified application scenarios require microwaves absorption materials (MAMs) with robust environmentally adaptive, but efficiently integrating multifunctionality within single MAMs is extremely challenging.Herein, a multifunctional CoC@FeNiG-F nanocomposite is fabricated by synergistic strategy of in situ growth, C-F•••π interaction and microwave irradiation.The MAMs exhibit a strong reflection loss of À75.18 dB with 3.95 GHz effective absorption bandwidth benefited from magnetic-dielectric attenuation, impedance matching, and multiple-reflection loss.Remarkably, it is first time to obtain the efficient MAMs accompanied with excellent mechanical (80.3 MPa), superamphiphobicity (153°and 151°), anticorrosion (45 d), and flame retardancy (V-0 rating), which illustrate that the combination of CoC@FeNiG 3D-skeleton and long-chain perfluorinated epoxy remarkably improve robust multifunctionality and environmentally adaptive.In particular, the MAMs are assembled into liquid-solid triboelectric nanogenerator, and the output performance (19.7 V, 1.68 μA) and durability (10 000s) are obviously improved benefiting from the trap effect of carbonized MOF.Therefore, this work provides an efficient guideline for designing advanced MAMs with robust environmentally adaptive and sustainable energy harvesting performance in extreme environment application.full of challenges.MetalÀorganic frameworks (MOFs) are crystalline materials consisted of metal ions and organic ligand with the high surface area and controllable structure. [7]And the carbonization of MOF precursors provided an optimal strategy for fabricating the magnetic nanoparticles/porous carbon nanofiller with adjustable component and diverse structure, and simultaneously improve the dispersibility and ameliorate stacking.Yang et al. fabricated CoNC@CF with hierarchical heterogeneous structures via self-assembly and autocatalytic pyrolysis process, which exhibit high MA performance with RL min is À50.1 dB and EAB is 4.82 GHz. [8]In addition, great efforts have been made in the combination of magnetic bimetallic/porous carbon and rGO/CNTs for further enhancing EMW attenuation performance owing to the more heterogeneous interfaces and absorption mechanisms, such as FeCo@NC/NCR/rGO, [9] NiFe@N-C/rGO, [10] and CNT-CoFe@C. [11]espite these advances, most MAMs are largely unsatisfactory in terms of environmentally adaptive in harsh environment, multifunctional requirements, and preparation feasibility, which restrict their advanced application.Accordingly, the compounding of EMW absorption nanomaterials into designed polymer matrix is an attractive strategy for adapt to complex environment. [12,13]For instance, Jiang et al. reported a hierarchical MXene/Ni chain/ZnO array hybrid nanostructures deposit on cotton fabric which exhibit the durable self-cleaning (152°) and enhanced microwave absorption (À35.1 dB). [14]Das et al. fabricated 1-(3-aminopropyl) imidazole (API)-grafted XNBR/ MXene composites, which show the outstanding shielding efficiency, self-healing ability, thermal management, recyclability, and mechanical behavior. [15]Wang et al. synthesized Fe-MOF-rGO@EP composite with good microwave absorption performance (À43.6 dB) and highly efficient flame-retarding properties. [16]Nevertheless, the poor dispersion and interface compatibility significantly reduces the reinforcement efficiency and comprehensive performance.Therefore, it is essential to achieving a positive effect of the nanofiller for excellent EMW absorption and multifunctionality. [17]Remarkably, it is predicable that the effective of the integration of MOF-derived multidimensional carbon and functional epoxy can clearly strengthen the environmentally adaptive and broaden application scenarios of MAMs. [18]n addition, energy crisis has become world's most serious challenges with the rapidly spread of electrical equipment and wireless communication.Recently, the liquid-solid triboelectric nanogenerator (LS-TENG) based on the coupling effect of contact electrification and electrostatic induction has been utilized for self-charging power system, [19] ship draft detection, [20] and low-frequency ocean energy harvesting. [21]Notably, the combination of effective EMW absorption and energy harvesting is crucial to the sustainable development.Overall, the integration of robust environmentally adaptive, multifunctionality, and blue energy harvesting is the further development direction of MAMs for diversified application. [22]But so far, efficiently combining robust multifunctionality within single material is still extremely challenging which relies on the creative design of material components, structures, and interaction effect, and there have no reports of MAMs with robust environmentally adaptive and sustainable energy harvesting. [23]n this work, we fabricated the CoCNT and FeNirGO multidimensional nanofiller by in situ growth and high-temperature pyrolysis, and it was subsequently added to long-chain perfluorinated epoxy matrix (F8EP/PFOP) by C-F•••π interaction for obtaining CoC@FeNiG-F nanocomposites via microwave irradiation strategy, as illustrated in Scheme 1, and the specific use and alternatives of these components are listed in Table S1, Supporting Information.The MAMs exhibit a strong RL min of À75.18 dB with 3.95 GHz effective EAB benefited from magnetic-dielectric attenuation, impedance matching, and multiple-reflection loss.Remarkably, it is first time to obtain the efficient MAMs accompanied with excellent mechanical (80.3 MPa), superamphiphobicity (153°and 151°), anticorrosion (45 d), and flame retardancy (V-0 rating), wherein the synergistic effect of C-F•••π interaction and microwave irradiation enhances the dispersibility of nanofiller, interface bonding strength, and regular cross-linked structure, which is the foundation of reliable supporting nanocomposite.Furthermore, the combination of CoC@FeNiG 3D-skeleton and long-chain perfluorinated epoxy remarkably improves robust multifunctionality and environmentally adaptive due to the excellent dispersion and interfacial bonding.Finally, we assembled the 10 CoC@FeNiG-F nanocomposites into liquid-solid TENG for harvesting water energy (19.7 V, 1.68 μA, 59 LEDs, and 10 000s durability), and the output performance and stability are greatly improved benefiting from the trap effect of porous structure and transition-metal center of carbonized MOF.Surprisingly, there were no reports on MOF material for using in LS-TNEG and introducing the energy harvesting in MAMs.Therefore, this study opens up infinite possibilities for the complex applications of EMW absorption techniques.

Characterization of F8EP/PFOP Matrix, FeNirGO, and CoCNT
The 1 H and 13 C NMR spectra of DABPA and DADGEBA are shown in Figure S1, Supporting Information, which proved the successful preparation of DADGEBA.As shown in Figure 1a 1 , the peaks at 2560 cm À1 (S─H) and 1638 cm À1 (C═C) were disappeared, and 912 cm À1 (epoxy) and 1205 cm À1 (C─F) were appeared, which indicated that the click reaction of thiol groups and double bonds was completely achieved. [24]Besides, as shown in Figure 1a 2 and Figure S2, Supporting Information, the 1 H (1.88, 2.55, and 2.71 ppm), 13 C (22.41, 31.04 ppm), and 19 F NMR spectra indicated the F8EP was successfully synthesized.With increasing PFOP, the tensile strength and modulus of F8EP/PFOP matrix were first increasing and then decreasing (Figure 1b 1 ), which was consistent with E 0 (Figure S3, Supporting Information).And the tanδ (Figure 1b 2 ) and differential scanning calorimetry (DSC) curve (Figure S4, Supporting Information) illustrated that with increasing PFOP, the glass transition and the β-relaxation peaks move to the lower temperature.All of the F8EP/PFOP systems showed only one main peak in tanδ curves which indicated that F8EP has good thermodynamic compatibility with PFOP. [25]Furthermore, the river-like fracture morphologies indicated that PFOP can improve the toughness of F8EP matrix (Figure 1b 3 ).These results revealed that appropriate dangling chain could decrease vacant volume and increase cohesive energy (internal antiplasticization), [26] resulting in enhancement of strength, modulus, and toughness.Moreover, the static contact angles (Figure 1b 4 ) of water (118°-128°) and hexadecane (110°-121°) were increased due to the low surface energy fluorinated dangling segment.So, the F8EP/PFOP 10 was decided to fabricate nanocomposites for the best comprehensive performance.
the characteristic peaks located at 1350 and 1589 cm À1 in Raman spectroscopy (Figure 1d), which correspond to the disordered and graphitic carbon, respectively.The I D :I G of FeNirGO was decreased obviously from 1.10 to 0.99, and that of CoCNT was from 0.72 to 0.42, which was ascribed to the reduction of GO and the carbonization of Fe/Ni/Co MOF.Furthermore, the graphitized domain and residual defects were beneficial to improving the conductivity and polarization loss, thus enhancing the EMWs attenuation ability.The elemental chemical state of FeNirGO could be further investigated by XPS (Figure 1e 1,2 ), and the total spectrum revealed the presence of the C, O, N, Fe, and Ni elements.The three characteristic peaks of highresolution C 1s appeared at 284.8, 286.0, and 286.8 eV corresponded to the C─C/C═C, C─N, and C─O, respectively.Moreover, the related peaks at 397.4, 399.1, 400.8, and 402.2 eV of N 1s spectrum corresponded to pyridinic N, Fe/Ni-N, pyrrolic N, and graphitic N, respectively.And the pyridinic/pyrrolic N promoted the electronic polarization relaxation and defect polarization, while graphitic N increased the conductivity. [28]esides, the peaks at 711.2 and 718.4 eV of Fe 2p spectrum were ascribed to Fe 0 , and the peaks at 856.Furthermore, the magnetic hysteresis loops of FeNirGO and CoCNT are shown in Figure 1g; the saturation magnetization (M s ) was 67.1 and 27.4 emu g À1 and the coercivity (H c ) was 262.21 and 159.67 Oe, which demonstrated the excellent ferromagnetic property.As shown in Figure 1h, the residual quality at 800 °C of FeNirGO and CoCNT was 96.41% and 97.57%, respectively, which demonstrated the excellent thermal stability and processability of nanocomposites.The specific surface area of FeNirGO and CoCNT was 139.49 and 151.04 m 2 g À1 (Figure 1i 1 ), and pore size distribution (Figure 1i 2 ) indicated the presence of mesoporous structure.And the N 2 adsorptiondesorption isotherm of MOF precursors (Figure S6, Supporting Information) indicated that the collapse of inner structure and growth of metallic NPc result in decrease of surface area. [29]otably, the reasonable specific surface area and abundant porous structure not only provide multiple reflections and scattering of EMWs, but also beneficial to the impedance matching, which further enhanced the attenuation of EMWs. [30]s shown in Figure 2a 1,2 , the clavate precursors uniformly grew on the surface of rGO, indicating the successfully compounding of the FeNi-GO.And the framework slightly collapsed and formed rough surface (Figure 2b 1 ) because the clavate precursor was converted into FeNi alloy nanoparticles, N-doped carbon nanorod, and rGO after calcination. [31]Clearly, the FeNi alloy nanoparticles embedded within N-doped carbon nanorod and rGO (Figure 2b 2 ), and Figure 2b 3,4 confirmed the formation of core-shell heterojunctions.Furthermore, these plentiful heterogeneous interfaces and defects could effectively promote the interface polarization loss. [32]The high resolution transmission electron microscope (HRTEM) images (Figure 2b 4 ) revealed that the lattice spacing of 0.254, 0.18, and 0.34 nm corresponded to (110), (200), and (002) lattice plane of FeNi and N-doped carbon, respectively, and the diffraction concentric rings (Figure 2b 5 ) further corresponded with XRD results.Moreover, the energy dispersive spectrometer (EDS) mapping images confirmed the uniform distribution of C, Fe, Ni, and N in the FeNirGO (Figure 2b 6 ).The SEM and transmission electron microscope (TEM) images of CoCNT were similar to FeNirGO (Figure 2c,d).Therefore, all of these results revealed that F8EP/PFOP matrix, FeNirGO, and CoCNT were successfully prepared.

Mechanical Properties
Figure 3a shows the micrographs of CoC@FeNiG-FEP suspension after standing for 24 h at room temperature, and the nanofiller was homogeneously distributed without precipitation and aggregation except for 14 CoC@FeNiG.And the mechanism of C-F/π interaction is shown in Figure S7, Supporting Information, which was formed by overlapping the aromatic with fluorinated segment. [33]Furthermore, the viscosities kept at a low level over the wide temperature range (Figure 3b), which was important for high loading content and excellent processability.The schematic of the microwave effect is illustrated in Figure S8, Supporting Information; overall, microwave irradiation promoted the uniform dispersion, interface bonding strength, and regular cross-linked structure, which resulted in the effective stress transfer network and conductive path. [34]Therefore, the synergy of microwave thermal and nonthermal effect could accelerate the large-scale preparation of high-performance CoC@FeNiG-F nanocomposites. [1,34]eanwhile, the cross-linked mechanism is shown in Figure 3c; the multidimensional carbon nanofillers interacted with FEP with the multifluorination dangling chain for enhancing interfacial bonding. [24]The CoC@FeNiG nanofiller could enhance the thermal stability (Figure 3d), which attributed to the well dispersion, strong interface bonding and multidimensional framing retarded the thermal degradation process. [35]The E 0 and tanδ curves are shown in Figure 3e, and E 0 (25 °C) of 6-14 CoC@FeNiG-F increased by 43.9%, 87.4%, 135.3%, 105.6%, 83.2%, and T g was increased by 8.6%, 13.9%, 22.6%, 18.3%, 10.4% compared with FEP, respectively.Besides, the E 0 and T g of 10 CoC@FeNiG-F were also higher than that of CoCNT-F and FeNirGO-F.And the DSC curves (Figure S9, Supporting Information) also revealed the same trend.Meanwhile, the tanδ peak intensity decreased with the increase of CoC@FeNiG, which indicated the enhancement of load transfer efficiency.The mechanical properties of CoC@FeNiG-F are shown in Figure 3f,g, and the tensile strength, modulus, and impact strength were increased by 24.4% (64.5-80.3MPa), 52% (2.5-3.8GPa), 48.6% (25.7-38.2kJ m À2 ) compared with FEP; 22.9%, 46.1%, 39.9% compared with CoCNT-F; 16.2%, 22.6%, 25.6% compared with FeNirGO-F, respectively.Therefore, it was obvious that the designed 3D network structure of CoC@FeNiG skeleton possessed the multidimensional synergistic enhancement effect on epoxy nanocomposites.
Furthermore, the enhanced mechanism of CoC@FeNiG nanofiller was investigated by fracture surface.The CoC@FeNiG nanocomposites appeared rougher morphologies, some pulled out CNTs/rGO and many smaller dimples compared with the river-like fracture surface of FEP, and the pits gradually increased with the increasing loading, which enriched the crack propagation path and energy consumption (Figure 3h and S10, Supporting Information). [36]However, relatively large dimples were appeared due to the agglomeration, which induced the microcracks aggregates into unified cracks and negative effect of strength (Figure S11, Supporting Information). [25,26]s shown in Figure 3h 2,3 , the perfectly dispersed CNTs/Co NPc/FeNi nanorods tethered onto rGO, which inhibited the stacking and aggregation.The interlocked structure and strong bonding interface were formed by hybrid CoC@FeNiG 3D-skeleton which strengthened effective stress transfer.And the 3D-skeleton structure served as bridge and hindered propagation of cracks, which caused crack blunting, pinning, propagation, and deflection, resulting in the improvement of toughness and strength. [24,37]The asymmetrical roughness, stacking of nanofiller and some smooth sections were observed in the fracture surface of 10 FeNirGO-F and CoCNT-F (Figure S12, Supporting Information), which indicated the ductile fracture was restricted.In summary, mechanical enhancement could be attributed to these aspects: the synergistic effect of C-F/π interaction, microwave irradiation, and multidimensional nanocarbon promoted the perfect dispersion of nanofiller; PFOP as dangling chains enhanced the internal antiplasticization effect; [26,35] microwave irradiation and CoC@FeNiG 3D-skeleton enhanced the interfacial bonding, which improved mechanical interlocking and stress transferring efficiency.
As shown in Figure 4a 1 , the ε 0 of all composites gradually declines with the increasing frequency (2-18 GHz) due to the typical electric dispersion phenomenon, [6] and the ε 00 /tanδ e (Figure 4a 2 and S13, Supporting Information) fluctuated at different frequency as result of polarization relaxation.It is clear that with the increase of addition amounts CoC@FeNiG, the ε 0 increased and ε 00 /tanδ e increased first and then decreased, and the strong resonance at different frequencies resulting from the high conductive loss and significant skin effect (Figure S14, Supporting Information).Furthermore, the ε 0 and ε 00 of the 10 CoC@FeNiG-F were evidently enlarged compared with 10 CoCNT-F and FeNirGO-F (Figure S15, Supporting Information), as the synergistic effect of conduction loss and polarization loss. [8]The complex permeability (μ 0 and μ 00 ) of the CoC@FeNiG-F nanocomposites were shown in Figure 4a 3 and S16, Supporting Information, and it was similar with the complex permittivity.Moreover, the 10 CoC@FeNiG-F composites exhibited relatively high μ 0 and μ 00 compared to 10 CoCNT-F and FeNirGO-F (Figure S17, Supporting Information), which attributed to the stronger magnetic response behavior of the multiple magnetic coupling networks.Obviously, the values of tanδ m (Figure 4a 4 ) were higher than tanδ e at the low frequency (2-8 GHz) for all CoC@FeNiG-F nanocomposites, which indicated the absorption was dominated by magnetic loss.On the contrary, the dielectric loss became dominant at the high-frequency range (8-18 GHz). [38]ccording to the transmission-line theory, [3] the reflection loss (RL) was introduced for estimate the EMA ability of the nanocomposites specifically where Z in is the normalized input impedance, f is the electromagnetic frequency, d is the thickness of the sample, and c is the velocity of light. [5]Generally, the minimum RL and EAB (RL ≤ À10 dB) are two basic indicators for evaluating EMW-absorbing performance.The RL min of 10 CoCNT-F and FeNirGO-F was À26.36 and À51.76 dB (Figure S18, Supporting Information) with the thickness of 1.8 and 5.8 mm, respectively.Just as expected, the EMW attenuation of CoC@FeNiG-F nanocomposites (Figure 4b) was effectively improved, the 10 CoC@FeNiG-F nanocomposites possessed RL min reaching À75.19 dB (>99.99999%absorption), and EAB was 3.95 GHz with 2.4 mm.The 14 CoC@FeNiG-F showed the depressed EMW absorption capacity (À44.95dB) due to the excessive amount of nanofiller formed the displacement current and impedance mismatch.Furthermore, for CoC@FeNiG-F nanocomposites, the RL min absorption peak shifted to lower frequencies as the thickness increased (Figure 4c 1 -c 5 ), which could be explained by the quarter-wavelength matching model [12] t m ¼ nc 4f m ffiffiffiffiffiffiffiffi μ r ε r p ðn ¼ 1, 3, 5, : : : Þ Obviously, the discrete points consisting of the frequency corresponding to the peak of the RL min curve and the corresponding thickness were ideally located on the λ/4 curve, which indicated that the phase of the incident EMW is 180°out of the phase with the reflected wave; [39] the EMW is attenuated due to interference cancellation.
The EMW attenuation ability was closely related to dielectric loss and magnetic loss, and the dielectric loss usually includes conductivity loss and polarization loss. [2,5]And the ion and electronic polarization often happen at higher frequencies ranging from 10 3 to 10 6 GHz, so the polarization loss was determined by the dipolar and interface polarization in 2-18 GHz.According to the Debye relaxation theory, [7] the ε 0 and ε 00 could be expressed as where ε s was the static permittivity and ε ∞ was relative permittivity.The relationship curve between ε 0 and ε 00 was a semicircle, and it was defined as a Cole-Cole semicircle which corresponded to a Debye relaxation process, and the Cole-Cole curves for CoC@FeNiG-F, 10 CoCNT-F and FeNirGO-F are shown in Figure 4d and S19, Supporting Information, respectively.
It is worth noting that some distinguishable semicircles of CoC@FeNiG-F nanocomposites revealed the presence of multiple dipolar relaxation processes. [4,8]The multiple heterogeneous interfaces enhanced the interfacial polarization, and the polar functional groups, nitrogen heteroatom, and defects as the polarization centers generated dipolar polarization. [40]Moreover, the tendency of this tail of the Cole-Cole curve becomes longer with the increased of electrical conductivity (Figure S20, Supporting Information), which confirmed the strengthening of the conductive loss.Generally, the magnetism loss was composed of natural resonance, eddy current loss, exchange resonance, domain wall resonance, and magnetic hysteresis. [2,12]And the domain wall resonance and magnetic hysteresis were negligible in the gigahertz range.The contribution of eddy current loss can be expressed by the C 0 The C 0 value (Figure 4e) of the CoC@FeNiG-F nanocomposites remained constant in the high-frequency band (12-18 GHz), which indicated that magnetic loss was dominated by the eddy current loss.Furthermore, the resonance peaks of 2-6 and 6-12 GHz (μ 00 ) were attributed to the natural resonance and exchange resonance, respectively.Moreover, the impedance matching (Z ) and attenuation constant (α) were essential parameters to evaluate the EMWs absorption ability As shown in Figure 4f and S21, Supporting Information, the CoC@FeNiG-F nanocomposites possessed more frequency band (1.2 > Z > 0.8) compared with the CoCNT-F and FeNirGO-F nanocomposites (Z < 1), and it was more favorable for the EMW to enter the absorber.Furthermore, the largest α value of the 10 CoC@FeNiG-F among the nanocomposites (Figure 4g and Figure S22, Supporting Information) indicated the best dissipation capacity to EMW.Thus, the superior EMW absorption of CoC@FeNiG-F could be attributed to the proper electrical conductivity and denser magnetic coupling network.
Based on the above discussion, the attenuation mechanism of CoC@FeNiG-F nanocomposite is illustrated in Figure 4h.First, the introduction of 2D rGO, 1D CNTs, and carbon nanorods with a higher aspect ratio established the 3D interconnected conducting network, which was beneficial to the migration and hopping of electrons, thus improving conductive loss.Second, the multiple heterogeneous interfaces between the FeNi/Co@graphitic carbon heterojunctions, carbon nanorods and rGO, Co dodecahedron nanocrystals, and CNTs enhanced the interfacial polarization.Furthermore, the polar functional groups (C─O, C═O), nitrogen heteroatom (pyrrolic N, pyridinic N), and defects of 3D porous structure as the polarization centers promoted dipolar polarization. [1,5]Meanwhile, uniformly distributed Fe/Ni/Co nanoparticles generated denser magnetic coupling network, and effectively improved EMW absorption via multiple resonances and eddy current.In addition, the synergistic effect between Fe/Ni/Co magnetic nanoparticles, porous carbon, CNTs, and rGO was beneficial for optimized impedance matching.Finally, the interfaces and 3D porous structures could enhance the multiple reflection.Furthermore, the thermal conductivity is illustrated in Figure S23, Supporting Information, and the thermal conductivity of 10 CoC@FeNiG-F was significantly increased to 1.17 W m À1 K À1 compared with EP, which indicated that the 10 CoC@FeNiG-F could obviously reduce heat accumulation during the EMW absorption process.

Superamphiphobicity, Anticorrosion, and Flame-Retardancy Performance
The robust environmentally adaptive of 10 CoC@FeNiG-F nanocomposite in harsh conditions was important for engineering applications.Thus, the performance and mechanism of the excellent superamphiphobicity, anticorrosion, and flame retarding were researched and discussed in detail.
The CoC@FeNiG-F nanocomposite coatings were fabricated by scrape coating and microwave irradiation (Figure S24, Supporting Information).As shown in Figure 5a 1 , the WCA (water) were 142°, 147°, 153°, 151°, 145°and OCA (hexadecane) were 135°, 144°, 151°, 147°, 142°of 6-14 CoC@FeNiG-F, respectively, and the sliding angle %5°, 7°(Figure S25, Supporting Information), which showed the low-adhesive property.The micro/nanoscale rough structures and uniform reentrant texture of 10 CoC@FeNiG-F nanocomposite is observed in Figure 5a 2 , and the height image (Figure 5a 3 ) also indicates the roughness with R a of 155.1 nm.Furthermore, based on the Cassie-Baxter models the f a of 10 CoC@FeNiG-F coating was 0.783 and 0.771, which implied that abundant sealed small air pockets trapped between the coating and contacting liquid. [41]The excellent superamphiphobicity performance due to the synergistic combination of hybrid micro/nanoscale rough structure by CoC@FeNiG 3D-skeleton, the low surface energy of the perfluorinated segment and abundant air pockets. [42]n addition, the mechanical robustness and chemical resistance were crucial for practical application, and the mechanical robustness was evaluated by sandpaper abrasion and tapepeeling experiment. [24]The 10 CoC@FeNiG-F coating loaded with 200 g balance weights was placed face-down on 320 Cw sandpaper (Figure S26, Supporting Information), and the WCA were 149, 146, 142, 139°, OCA were 146, 142, 135, 131 o for 200, 400, 600, 800 cm abrasion distance (Figure 5b 1 ), respectively, and the θ SA % 14, 15°(800 cm, Figure S27, Supporting Information), which indicated that the surface still possessed good liquid repellency with the slight morphological corrosion.Significantly, the residual structures (Figure 5b 2 ) and height image (Figure S28, Supporting Information) of attrite surface illustrated the excellent micro/nanoscale roughness and low surface energy components retention capability. [43]Furthermore, the 10 CoC@FeNiG-F coating maintained the excellent liquid repelling with WCA % 142 o , OCA % 140°, and θ SA % 12°, 14°after 120 cycle tape-peeling experiment (Figure 5c), which reflected the good stabilities and interface compatibility.As shown in Figure 5d 1 , the WAC and OCA still remained at 147°and 143°, 151°and 147°, 143°and 141°after 0.1 M HCl, NaCl, and NaOH solution 12 h immersion, respectively.And the surface still possessed dynamic liquid-repelling behavior (Figure S29, Supporting Information).Significantly, the residual low surface energy micro/nanoscale structures after HCl solution immersion is shown in Figure 5d 2 , which indicated that the perfluorinated segment and CoC@FeNiG 3D-skeleton formed cluster to resist corrosion and retained roughness.Besides, the 10 CoC@FeNiG-F coating still possessed good liquid repellency after exposed to the flame (%500 °C) as long as 15 s (Figure 5e), which indicated the excellent thermal stability and flame retardancy.Moreover, the 10 CoC@FeNiG-F coating could maintain excellent liquid repellency in thermal-oxidative aging, UV radiation, and ultrasonic condition (Figure 5f-h).Overall, the 10 CoC@FeNiG-F coating showed the excellent micro/nanoscale robustness and chemical resistance in response to uniform dispersion of nanofiller, strong interfacial bonding strength, stable CoC@FeNiG 3D-skeleton, and multifluorination strategy.When the water was pressed on the surface, it neither wetted or adhered and could be easily picked up (Figure 5h), which showed low adhesion and potential of self-cleaning.Thus, when the water was dropped on the 10 CoC@FeNiG-F coating, the contaminants were easily carried away by the rolling water droplets, leaving a clean and dry surface (Figure 5i), which was consistent with the "lotus effect." [14,24,42]he potentiodynamic polarization curves are shown in Figure S30, Supporting Information; the 10 CoC@FeNiG-F coating possessed the most positive E corr (À0.464V Ag/AgCl) and lower i corr (3.12 Â 10 À8 A cm À2 ) which revealed that the effective corrosion resistance due to inhibiting both anodic and cathodic reaction.The electrochemical impedance spectroscopy was used to further investigate long-term anticorrosion performance of each coating. [44]The impedance modulus (|Z| 0.01 , ionic and electronic barrier ability), breakpoint frequency ( f b , microscopic corrosion area), and capacitive loops (corrosion resistance) of the EP coating deteriorated rapidly after 3 d (Figure S31, Supporting Information), and the FEP coating exhibited a better corrosion inhibition behavior (Figure S32, Supporting Information), which indicated that the excellent hydrophobic shielding performance delayed the infiltration of corrosive media. [45]As shown in Figure 6a 1, b 1 , the |Z| 0.01 of Figure 5. a 1 ) WCA and OCA of CoC@FeNiG-F coatings.a 2 ) AFM height image and a 3 ) SEM surface morphology of 10 CoC@FeNiG-F coating.b 1 ) WCA and OCA after different distance sandpaper abrasion.b 2 ) SEM surface image after 800 cm abrasion.c) WCA and OCA after the tape-peeling test.d 1 ) WCA and OCA after corrosion in 0.1 M HCl, NaCl, and aqueous solutions.d 2 ) SEM surface morphology after HCl solution immersion.The WCA and OCA after e) exposed to the inner flame (%500 °C), f ) thermal-oxygen aging, g) UV irradiation, and h) ultrasonic.i) Diagram of the process of water droplet touching, depressing, and detaching.j) Self-cleaning performance.phase significantly enhanced the fire safety properties of 10 CoC@FeNiG-F nanocomposite.
The contact electrification and charge transfer mechanism could be explained by electron-cloud-potential-well and electric double-layer (EDL) model. [53]As shown in Figure 8a 1 , when the electron clouds of 10 CoC@FeNiG-F and H 2 O were separated, their electrons were bound to atomic orbitals with high escape energy barriers. [54]As the water drop moved, the electron clouds were overlapped strongly and formed the asymmetric double potential well.Some electrons escaped form orbit and were attracted by another material with different affinity of charge due to the potential barrier was decreased, [19,55] and the porous structure of CoC@FeNiG 3D-MOF-frameworks promoted charge-trapping and charge-transport.Thus, the transferred charges were retained stably in 10 CoC@FeNiG-F surface as electrostatic charges after separated.The formation of the EDL is shown in Figure 8a 2 , and the free ions of water were attracted by the electrostatic interaction [20,54] to the 10 CoC@FeNiG-F surface.And cationic hole (H 2 O þ ) was produced when the water molecule lost an electron, and it formed further an OH radical and H 3 O þ . [56]Meanwhile, the cations were attracted by solid surface and maintained electrostatic equilibrium by the formation of positive charge layer. [19,21]Furthermore, freely migrating ions and ionization result in the charge distribution and compensation in the diffusion layer.The working mechanism of LS-TNEG is illustrated in Figure 8b, which is based on the coupling effect of triboelectrification and electrostatic induction. [54,56]The falling droplet generated positive charge when rubs with air. [55]uccessively, the current with opposite was generated to satisfy the e potential equilibrium when the droplet flowed away from bottom of electrode.Meanwhile, the electrons flowed from electrode A to B due to electrostatic induction.Successively, the current with opposite was generated to satisfy the e potential equilibrium when the droplet swept away form bottom. [21,53] As a result, this process generated an AC pulse output and continuous droplet would provide continuous electric output.
We used KPFM to investigate the surface potentials, and Figure 8c 1,2 and S33, Supporting Information, reveal the order: 10 CoC@FeNiG-F (714.7 mV) > 10 C@G-F (264.0 mV) > FEP (112.5 mV).The 10 CoC@FeNiG-F possessed the significant negative polarity which result in higher electrical output in LS-TNEG, and it attributed to the porous structure of CoC@FeNiG 3D-MOF-frameworks promoted charge-trapping/ storage and induced charges density, regular perfluorinated segment, and micro/nanoscale rough structures. [57]For practical application, the influence of dropping height, tilt angle, and water flowrate on output performance was investigated.Figure 8d 1,2 illustrates open-circuit voltage and short-circuit current of the LS-TENG at different dropping heights, and the output performance increased from 7.2 V/0.81 μA to 18.7 V/1.57μA with the increase of dropping height.In addition, the optimal voltage/current was 19.2 V/1.63 μA when the θ was 30°(Figure 8e 1,2 ); this is because the remaining drops would influence electrostatic induction effect of subsequent drops (θ < 30°) and the reduction of effective contact surface area which results in triboelectric charge depressed (θ > 30°).Furthermore, the relationship between flowrate and output capability is shown in Figure 8f 1,2 , and the flowrate was controlled by peristaltic pump.Obviously, the output performance increased from 7.8 V/0.47 μA to 19.7 V/1.68 μA with flowrate increased from 20 to 60 mL min À1 .The higher flowrate could generate more triboelectric charges and faster forming rate of EDL, which achieved excellent electrical properties.Besides, the relationship between the peak voltage, current, and power versus load resistances is shown in Figure 8g with the 20 cm dropping height, θ = 30°, and 60 mL min À1 flowrate.As a result, the maximum output power achieved 31.85 μW at the resistance of 10.4 MΩ.Especially, the LS-TENG could charge different capacitors and  and c) charge transfer mechanism of the 10 CoC@FeNiG-F LS-TENG.The surface potential of c 1 ) 10 C@G-F and c 2 ) 10 CoC@FeNiG-F.d 1 ,e 1 ,f 1 ) Output voltage and d 2 ,e 2 ,f 2 ) current of different dropping heights, tilt angle, and water flowrate, respectively, g) instantaneous power, h) charging curves for various capacitors, i) LEDs illumination, and j) stability test of 10 CoC@FeNiG-F LS-TENG.
the voltage reached up to 12 V within 150 s (1 μF, Figure 8h), and it could illuminate 59 LEDs brightly ("BUCT CJ", Figure 8i).Moreover, Figure 8j illustrates the electrical performance remained basically constant without obvious fluctuations which indicated the excellent durability.All results revealed that the LS-TENG based on 10 CoC@FeNiG-F was highly promising for large-scale water energy harvesting and applications.Combining EMW absorption, superhydrophobic, long-term anticorrosion, flame retardancy, and liquid energy harvesting, the 10 CoC@FeNiG-F nanocomposite provided an attractive perspective for the sustainable development in various fields in the future.

Conclusion
In summary, the robust environmentally adaptive and sustainable energy harvesting CoC@FeNiG-F nanocomposite was successfully fabricated by synergistic strategy of in situ growth, C-F•••π interaction, and microwave irradiation.The MAMs exhibit a strong RL min of À75.18 dB with 3.95 GHz effective EAB benefited from magnetic-dielectric attenuation, impedance matching, and multiple-reflection loss.Additionally, the material shows remarkable mechanical, superamphiphobicity, selfcleaning, anticorrosion, and flame retardancy, which illustrate that the combination of CoC@FeNiG 3D-skeleton and longchain perfluorinated epoxy remarkably improve robust multifunctionality and environmentally adaptive.Finally, the MAMs was assembled into LS-TENG; the excellent output performance and durability was benefiting from the trap effect of porous structure and transition-metal center of carbonized-MOF.In particular, compared with the other reported MAMs, CoC@FeNiG-F nanocomposite presented the state-of-the art EMW absorption, superhydrophobic, long-term anticorrosion, and flame retardancy performance, respectively (Figure S34 and Table S2-5, Supporting Information).Surprisingly, there were no reports on MOF material for using in LS-TNEG and introducing the energy harvesting in MAMs.Therefore, this work provided new inspiration and insights for the preparation of robust multifunctional MAMs, which provided great potential for further application in aerospace and ocean equipment, hightemperature and flame environment, blue energy harvesting, wireless communications, and portable electronics.
7 and 872.4 eV of Ni 2p spectrum were ascribed to Ni 0 .In the same way, the total spectrum of CoCNT (Figure 1f 1,2 ) revealed the presence of the C, O, N, and Co elements, and the characteristic peaks at 397.7, 399.3, 400.5, and 401.8 eV of N 1s spectrum corresponded to pyridinic N, Co-N, pyrrolic N, and graphitic N, respectively.Besides, the peaks of Co 0 (778.4eV), Co 2p 3/2 (779.6 eV), and Co 2p 1/2 (794.4eV) were ascribed to the existence of metallic Co.These results were further confirmed that Fe 3þ , Ni 2þ , GO, Co 2þ , and COOH-CNTs were effectively reduced by the high-temperature pyrolysis (Figure S5, Supporting Information).