Tunable Chemical Structures Research Articles

3D Printed Metal Organic Framework Hydrogel for Dye Adsorption and Gas Sensing

AbstractMetal organic frameworks (MOFs) have tunable chemical structures, orderly pore structures, and modifiable surface functional groups making them a promising material for environmental remediation. However, their rigid powder morphology poses significant challenges for customizing MOF structures with adjustable mechanical properties. Here, we synthesis the stretchable UV‐curable MOF hydrogels through high‐resolution digital light processing 3D printing, and evaluated its adsorption effect on seven common dyesand.The results showed that it had selective adsorption effect on methylene blue (MB), and the adsorption effect increased with the increase of the initial concentration of MB: its adsorption capacity on 6 mgL−1, 12 mgL−1 and 24 mgL−1 MB solution reached 13.55 mgg−1, 26.31 mgg−1 and 50.70 mgg−1 respectively. Compared to powdered MOFs, the 3D‐printed MOF (Cu‐BTC) exhibited superior adsorption for dye and radioactive pollution, with methylene blue adsorption increasing from 8.93 mgg−1 to 25.05 mgg−1 and I2 adsorption from 141.56 mgg−1 to 792.65 mgg−1. Furthermore, the 3D‐printed MOF structure proved easily cleanable with dilute HCl and reusable over five times without degradation. In addition, our study highlighted the suitability of the 3D‐printed MOF for CO2‐sensing devices, demonstrating its broad applicability in environmental remediation and sensing technology.

Metal-Organic Frameworks (MOFs) and Metal-Organic Cages (MOCs) for Photocatalytic Hydrogen Production.

Metal-organic frameworks (MOFs) and metal-organic cages (MOCs) have garnered significant attention as promising photocatalysts due to their tunable chemical structures and integrated multifunctionality. To increase the photocatalytic efficiency, strategies like ligand functionalization, introducing additional catalytic sites, and doping or encapsulating photosensitizers have been explored for both MOFs and MOCs. This concept review focuses on recent advancements in utilizing MOFs and MOCs for photocatalytic hydrogen production, highlighting their unique characteristics and introducing their respective mechanisms in this field. Moreover, it outlines the current challenges and prospects faced by MOFs and MOCs, offering an outlook on their future in this domain.

Heterogeneous Porous Synergistic Photocatalysts for Organic Transformations.

Recent interest has surged in using heterogeneous carriers to boost synergistic photocatalysis for organic transformations. Heterogeneous catalysts not only facilitate synergistic enhancement of distinct catalytic centers compared to their homogeneous counterparts, but also allow for the easy recovery and reuse of catalysts. This mini-review summarizes recent advancements in developing heterogeneous carriers, including metal-organic frameworks, covalent-organic frameworks, porous organic polymers, and others, for synergistic catalytic reactions. The advantages of porous materials in heterogeneous catalysis originate from their ability to provide a high surface area, facilitate enhanced mass transport, offer a tunable chemical structure, ensure the stability of active species, and enable easy recovery and reuse of catalysts. Both photosensitizers and catalysts can be intricately incorporated into suitable porous carriers to create heterogeneous dual photocatalysts for organic transformations. Notably, experimental evidence from reported cases has shown that the catalytic efficacy of heterogeneous catalysts often surpasses that of their homogeneous analogues. This enhanced performance is attributed to the proximity and confinement effects provided by the porous nature of the carriers. It is expected that porous carriers will provide a versatile platform for integrating diverse catalysts, thus exhibiting superior performance across a range of organic transformations and appealing prospect for industrial applications.

Interfacially initiated polymerization of epoxides: A thin-film synthesis platform for XLPEO gas separation membranes

Crosslinked poly (ethylene oxide) (XLPEO) membranes are leading candidates for membrane post-combustion carbon capture, because of their high CO2/N2 selectivity and CO2 permeability. However, their crosslinked nature makes it difficult to process them into thin films through conventional coating techniques. In this study, interfacially initiated chain growth polymerization of epoxides is used to circumvent the XLPEO processing challenge whilst allowing in-situ crosslinking. The interfacial design strategy yields intrinsically crosslinked, epoxide-based PEO (eXLPEO) thin-film composite gas separation (GS) membranes consisting fully of CO2-philic ether bonds. An eXLPEO selective layer made from poly (ethylene glycol) diglycidyl ether was successfully deposited on a PAN support and, after introduction of densification steps and a PDMS sealing, gas selective membranes were obtained. Synthesis-structure-performance analysis revealed that multiple reaction condition combinations result in highly selective membranes with a tunable chemical structure. The best performing membranes showed CO2/N2 separation factors of 58 at 35 °C, with a stable operation at pressures from 2 to 10 bar, and retaining a separation factor of 30 at 65 °C. However, all membranes had a low CO2 permeance (<10 GPU), probably due to pore impregnation of the support layer. This work demonstrates for the first time the viability of interfacial polymerization for the synthesis of thin film eXLPEO GS membranes.

Tuning grain boundary cation segregation with oxygen deficiency and atomic structure in a perovskite compositionally complex oxide thin film

Compositionally complex oxides (CCOs) are an emerging class of materials encompassing high entropy and entropy stabilized oxides. These promising advanced materials leverage tunable chemical bond structure, lattice distortion, and chemical disorder for unprecedented properties. Grain boundary (GB) and point defect segregation to GBs are relatively understudied in CCOs even though they can govern macroscopic material properties. For example, GB segregation can govern local chemical (dis)order and point defect distribution, playing a critical role in electrochemical reaction kinetics, and charge and mass transport in solid electrolytes. However, compared with conventional oxides, GBs in multi-cation CCO systems are expected to exhibit more complex segregation phenomena and, thus, prove more difficult to tune through GB design strategies. Here, GB segregation was studied in a model perovskite CCO LaFe0.7Ni0.1Co0.1Cu0.05Pd0.05O3−x textured thin film by (sub-)atomic-resolution scanning transmission electron microscopy imaging and spectroscopy. It is found that GB segregation is correlated with cation reducibility—predicted by an Ellingham diagram—as Pd and Cu segregate to GBs rich in oxygen vacancies (VO··). Furthermore, Pd and Cu segregation is highly sensitive to the concentration and spatial distribution of VO·· along the GB plane, as well as fluctuations in atomic structure and elastic strain induced by GB local disorder, such as dislocations. This work offers a perspective of controlling segregation concentration of CCO cations to GBs by tuning reducibility of CCO cations and oxygen deficiency, which is expected to guide GB design in CCOs.

Conjugated Microporous Polymers for Catalytic CO2 Conversion.

Rising carbon dioxide (CO2) levels in the atmosphere are recognized as a threat to atmospheric stability and life. Although this greenhouse gas is being produced on a large scale, there are solutions to reduction and indeed utilization of the gas. Many of these solutions involve costly or unstable technologies, such as air-sensitive metal-organic frameworks (MOFs) for CO2 capture or "non-green" systems such as amine scrubbing. Conjugated microporous polymers (CMPs) represent a simpler, cheaper, and greener solution to CO2 capture and utilization. They are often easy to synthesize at scale (a one pot reaction in many cases), chemically and thermally stable (especially in comparison with their MOF and covalent organic framework (COF) counterparts, owing to their amorphous nature), and, as a result, cheap to manufacture. Furthermore, their large surface areas, tunable porous frameworks and chemical structures mean they are reported as highly efficient CO2 capture motifs. In addition, they provide a dual pathway to utilize captured CO2 via chemical conversion or electrochemical reduction into industrially valuable products. Recent studies show that all these attractive properties can be realized in metal-free CMPs, presenting a truly green option. The promising results in these two fields of CMP applications are reviewed and explored here.

Comprehensive analysis of cationic dye removal from synthetic and industrial wastewater using a semi-natural curcumin grafted biochar/poly acrylic acid composite hydrogel.

Polymer composites offer a tailored framework as an exceptional candidate for water treatment due to their tunable chemical structure, porous 3D architecture, physiochemical stability, accessibility, pH-sensitivity and ease of use. In this study, curcumin-engineered biochar is embedded into a cross-linked polyacrylic acid hydrogel matrix using in situ polymerization for developing a semi-natural adsorbent for the removal of cationic dye from an aqueous solution. The physicochemical features of the generated composite hydrogel are significantly influenced by the implementation of curcumin-grafted biochar into the polyacrylic acid substrate. Comprehensive characteristic approaches were employed to explore all aspects of the adsorbent's properties, especially its removal efficacy. The methodical adsorption study was accomplished by monitoring dynamic factors such as pH, adsorbent content, time frame, and initial dye concentration. The presence of the porous aromatized structure of biochar, active oxygen-enrich functional groups (carboxyl, hydroxyl, keto, enol, ether) coupled with the conjugated curcumin structure facilitate the effective establishment of hydrogen bonds, electrostatic interactions, π-π interactions, electron donor-acceptor and charge-assisted H-bonding with the malachite green (MG) and rhodamine B (Rho) molecules. The highest adsorption capacities of MG and Rho reached 521 mg g-1 and 741 mg g-1 respectively, in the range of neutral pH, considering their molecular nature, functionalities, and unique adsorption mechanisms. The isothermal modeling was carried out with Henry, Langmuir, Jovanovic, Freundlich, Temkin, and Koble-Corrigan models to determine the adsorption system. Additionally, the kinetic data were assessed with Bangham, pseudo-first-order, pseudo-second-order, intra-particle, and liquid film diffusion models to ascertain the rate-limiting phase. The Koble-Corrigan and Langmuir isotherm models (R2 > 0.997) as well as pseudo-second-order (R2 > 0.998) and Elovich (R2 = 0.983 and 0.995) kinetics models provide a substantial level of concordance with empirical findings. The analysis of non-linear diffusion models revealed that the Bangham (R2 > 0.995) pore and liquid film diffusion (R2 > 0.960) models has major influence on the rate of the adsorption procedure. The binary adsorption test demonstrated higher efficacy of the synthesized adsorbent in the removal of malachite as compared to rhodamine. This study sheds light on the design of a cost-effective semi-natural polymeric composite for treating dye-polluted wastewaters, a major milestone toward environmental and ecological sustainability.

Boosting the oxygen reduction activity of non-metallic catalysts via geometric and electronic engineering through nitrogen and chlorine dual-doping.

The development of heteroatom dual-doped porous carbon frameworks with uniform doping is highly desirable for achieving highly efficient oxygen reduction reaction (ORR) activity, due to their tunable chemical and electronic structures. Herein, porous covalent triazine-based frameworks (CTFs) incorporating nitrogen/chorine dual-doped porous carbon networks were fabricated by selecting 1,3-bis(4-cyanophenyl) imidazolium chloride as a building block, in a facile and controllable way via a bottom-up strategy. The resulting nitrogen/chorine dual-doped catalyst CCTF-700 exhibits excellent ORR performance with a more positive onset and half-wave potential (0.85 V vs. RHE), higher diffusion-limited current density and significantly improved stability in comparison with the benchmark commercial 20 wt% Pt/C catalyst. It is worth mentioning that CCTF-700 shows one of the best ORR performances among all the reported metal-free electrocatalysts under alkaline conditions. This work paves the way for a controllable and reliable strategy to craft highly efficient heteroatom dual-doped carbon catalysts for energy conversion.

Dimensionality Engineering of Organic-Inorganic Halide Perovskites for Next-Generation X-Ray Detector.

The next-generation X-ray detectors require novel semiconductors with low material/fabrication cost, excellent X-ray response characteristics, and robust operational stability. The family of organic-inorganic hybrid perovskites (OIHPs) materials comprises a range of crystal configuration (i.e., films, wafers, and single crystals) with tunable chemical composition, structures, and electronic properties, which can perfectly meet the multiple-stringent requirements of high-energy radiation detection, making them emerging as the cutting-edge candidate for next-generation X-ray detectors. From the perspective of molecular dimensionality, the physicochemical and optoelectronic characteristics of OIHPs exhibit dimensionality-dependent behavior, and thus the structural dimensionality is recognized as the key factor that determines the device performance of OIHPs-based X-ray detectors. Nevertheless, the correlation between dimensionality of OIHPs and performance of their X-ray detectors is still short of theoretical guidance, which become a bottleneck that impedes the development of efficient X-ray detectors. In the review, the advanced studies on the dimensionality engineering of OIHPs are critically assessed in X-ray detection application, discussing the current understanding on the "dimensionality-property" relationship of OIHPs and the state-of-the-art progresses on the dimensionality-engineered OIHPs-based X-ray detector, and highlight the open challenges and future outlook of this field.

Defective Nickel–Iron Layered Double Hydroxide for Enhanced Photocatalytic NO Oxidation with Significant Alleviation of NO2 Production

Photocatalysis offers a sustainable means for the oxidative removal of low concentrations of NOx (NO, NO2, N2O, N2O5, etc.) from the atmosphere. Layered double hydroxides (LDHs) are promising candidate photocatalysts owing to their unique layered and tunable chemical structures and abundant surface hydroxide (OH−) moieties, which are hydroxyl radical (OH) precursors. However, the practical applications of LDHs are limited by their poor charge-separation ability and insufficient active sites. Herein, we developed a facile N2H4-driven etching approach to introduce dual Ni2+ and OH− vacancies (Niv and OHv, respectively) into NiFe-LDH nanosheets (hereafter referred to as NiFe-LDH-et) to facilitate improved charge-carrier separation and active Lewis acidic site (Fe3+ and Ni2+ exposed at OHv) formation. In contrast to inert pristine LDH, NiFe-LDH-et actively removed NO under visible-light illumination. Specifically, Ni76Fe24-LDH-et etched with 1.50 mmol·L−1 N2H4 solution removed 32.8% of the NO in continuously flowing air (NO feed concentration: ∼500 parts per billion (ppb)) under visible-light illumination, thereby outperforming most reported catalysts. Experimental and theoretical data revealed that the dual vacancies promoted the production of reactive oxygen species (O2− and OH) and the adsorption of NO on the LDH. In situ spectroscopy demonstrated that NO was preferentially adsorbed at Lewis acidic sites, particularly exposed Fe3+ sites, converted into NO+, and subsequently oxidized to NO3− without the notable formation of the more toxic intermediate NO2, thereby alleviating risks associated with its production and emission.

Self-assembled chitosan-sodium usnate drug delivery nanosystems: Synthesis, characterization, stability studies, in vitro cytotoxicity and in vivo biocompatibility against 143 B cells

Polymers are among the most studied materials as drug carriers, due to their tunable chemical structure and ability to self-assemble to give different types of nanostructures. In this study, chitosan (CS) nanoparticles (NPs) were investigated as carriers for the anticancer drug sodium usnate (NaU) for the treatment of osteosarcoma (OS), which is the most prevalent primary malignant bone sarcoma in pediatric and adolescent patients. CS nano-assembling was induced by electrostatic interactions with the drug and the anionic cross-linker tripolyphosphate, thus obtaining stable nanosystems and a high drug encapsulation efficiency. Importantly, a reduction in NaU hepatotoxicity when encapsulated in CS NPs compared to free NaU was evidenced, suggesting that CS may have a protective role against liver damage. Unfortunately, NaU encapsulation also reduced drug toxicity versus osteosarcoma 143B cells compared to free NaU. Nevertheless, NaU-loaded CS NPs (0.312 mg/mL) were found to decrease 143B cells viability after 48 h and 72 h treatment without being hepatotoxic. Interestingly, this system also stimulated in 143B cells Maspin production, an agent known for its tumor suppressor properties. Relevant synergistic activity between CS and NaU in promoting Maspin stimulation was found. That suggests the potential of the systems to reduce invasiveness of OS cancer.

Metal-Organic Frameworks Based Multifunctional Materials for Solar Cells: A Review

Developing low-cost and stable materials for converting solar energy into electricity is vital in meeting the world’s energy demand. Metal-organic frameworks (MOFs) have gained attention for solar cells due to their natural porous architectures and tunable chemical structures. They are built by high-symmetry metal clusters as secondary building units and organic carboxylate/azolate ligands as linkers. This review commences with an exploration of the synthetic methods of MOFs. Moreover, we discuss the various roles of MOFs, including photoanodes and counter electrodes in dye-sensitized solar cells and interfacial layers and charge carriers in perovskite solar cells. Additionally, studies involving the application of MOFs for OSC were additionally presented. Ultimately, burdensome tasks and possible directions for advancing MOFs-based nanomaterials are provided for solar cells.

Mechanochemical Synthesis of Stimuli Responsive Microgels.

Mechanochemical approaches are widely used for the efficient, solvent-free synthesis of organic molecules, however their applicability to the synthesis of functional polymers has remained underexplored. Herein, we demonstrate for the first time that mechanochemically triggered free-radical polymerization allows solvent- and initiator-free syntheses of structurally and morphologically well-defined complex functional macromolecular architectures, namely stimuliresponsive microgels. The developed mechanochemical polymerization approach is applicable to a variety of monomers and allows synthesizing microgels with tunable chemical structure, variable size, controlled number of crosslinks and reactive functional end-groups.

Mechanochemical Synthesis of Stimuli Responsive Microgels

AbstractMechanochemical approaches are widely used for the efficient, solvent‐free synthesis of organic molecules, however their applicability to the synthesis of functional polymers has remained underexplored. Herein, we demonstrate for the first time that mechanochemically triggered free‐radical polymerization allows solvent‐ and initiator‐free syntheses of structurally and morphologically well‐defined complex functional macromolecular architectures, namely stimuliresponsive microgels. The developed mechanochemical polymerization approach is applicable to a variety of monomers and allows synthesizing microgels with tunable chemical structure, variable size, controlled number of crosslinks and reactive functional end‐groups.

NHC-heterocycle carbene gold catalyst intercalated in Layered Double Hydroxides as reusable hybrid catalyst in acidic medium

NHC-heterocyclic carbene metal complexes are efficient catalysts used for the oxidation, amination, cycloaddition or hydration of alkynes. Immobilization of such complex is a strategy to avoid its decomposition/deactivation and allow its recycling. One limitation of the immobilization of carbene metal complexes is the acidic pH required to perform the catalysis of hydration of alkynes. The support used must be resistant in such conditions. Layered Double Hydroxides (LDH) is a widely used material as catalyst support due to their tunable chemical composition and flexible open structure. However, the LDH phases usually found as catalyst support in the literature are chemically instable under severe conditions. In particular, when operating in extreme acidic pH. This study describes the development of a pH-resistant support by screening of LDH with various composition and formulation in order to obtain a stable material at pH down to 3.0, conditions required for a model reaction, the hydration of propargyl alcohol. Then, the intercalation of a NHC-heterocyclic carbene gold anionic complex (NHC-Au) was optimized and fully characterized. The newly heterogeneous catalysts were evaluated for the targeted hydration catalysis reaction. The selected support, a LiAl2 phase obtained by urea method and dried at 80 °C, allowed to immobilized up to 75% of the gold complex. The intercalated catalyst was finally used for the hydration of several alkynes with yields between 84% and 100% and was recycled up to 12 cycles without any activity loss.

Exploring the Electroluminescent Applications of Imidazole Derivatives.

Recently, the fields of organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LECs) have improved tremendously with regard to tunable emission, efficiency, brightness, and thermal stability. Imidazole derivatives are excellent deep blue-green light-emitting layers in the OLED or LEC devices. This Review summarizes the major breakthroughs of various electroluminescence (EL) layers with imidazole-containing organic or organometallic derivatives, the molecular design principles, and their light-emitting performances as effective EL materials. The highly tunable chemical structures and flexible molecular design strategies of imidazole-based compounds are advantages that provide great opportunities for researchers. They can provide a good basis for the design and development of new EL materials with narrower emission and higher efficiency. Moreover, imidazole compounds have demonstrated breakthrough performances in thermally activated delayed fluorescence (TADF) properties where triplet excitons are utilized to inhibit anti-intersystem quenching, showing great promise in breaking the theoretical external quantum efficiencies (EQE) limits in traditional fluorescent devices.

Polyurea micro-/nano-capsule applications in construction industry: A review

Abstract The application of micro-/nano-capsules in construction industries has been rising over the past decade. Polyurea with tunable chemical and morphological structure are of interesting polymers to prepare micro-/nano-capsules used in construction. The structure of polyurea micro-/nano-capsule is capable to be tailored via bulk emulsion or microfluidic method. Important factors for production of micro/nano-capsules are the rate of fabrication and having control over mean size, dispersity, and wall thickness. The bulk emulsion method provides higher yield of production with less control over sizes and dispersity in comparison to microfluidic technique. The main applications of polyurea micro-/nano-capsules in construction industries are categorized as thermal energy saving, self-healing concrete, self-healing polymers, and fire retarding. Polyurea showed appropriate thermal conductivity and mechanical properties which is required for encapsulation of phase change materials. Titanium dioxide polyurea microcapsules possess energy storage efficiency of 77.3% and thermal storage capacity of 99.9%. Polyurea microcapsules with sodium silicate cargo provided self-healing abilities for oil well cement in high temperature and showed higher self-healing abilities compared to gelatin microcapsules. Graphene oxide polyurea micro-/nano-capsules demonstrated 62.5% anti-corrosive self-healing efficiency in epoxy coating, and steel coated via dendritic polyurea microcapsules embedded polyurethane remained unchanged after long time immersion in salt water.

Covalent organic frameworks with imine proton acceptors for efficient photocatalytic H2 production

Covalent organic frameworks (COFs) are promising crystalline materials for the light-driven hydrogen evolution reaction (HER) due to their tunable chemical structures and energy band gaps. However, deeply understanding corresponding mechanism is still challenging due to the multiple components and complicated electron transfer and reduction paths involved in photocatalytic HER. Here, the photocatalytic HER investigation has been reported based on three COFs catalysts, 1–3, which are prepared by benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-trialdehyde to react with C3 symmetric triamines including tris(4-aminophenyl)amine, 1,3,5-tris(4-aminophenyl)benzene, and (1,3,5-tris-(4-aminophenyl)triazine, respectively. As the isostructural hexagonal honeycomb-type COF of 2 and 3 reported previously, the crystal structure of 1 has been carefully correlated through the powder X-ray diffraction study with the help of theoretical simulations. 1 shows highly porous framework with Brunauer-Emmett-Teller surface area of 1249 m2/g. Moreover, the introduction of ascorbic acid into the photocatalytic system of COFs achieves the hydrogen evolution rate of 3.75, 12.16 and 20.2 mmol g–1 h–1 for 1–3, respectively. The important role of ascorbic acid in photocatalysis of HER is disclosed to protonate the imine linkages of these COFs, leading to the obvious absorbance red-shift and the improved charge separation efficiency together with reduced resistance in contrast to pristine materials according to the spectroscopic and electronic characterizations. These innovations of chemical and physical properties for these COFs are responsible for their excellent photocatalytic performance. These results elucidate that tiny modifications of COFs structures is able to greatly tune their band structures as well as catalytic properties, therefore providing an available approach for optimizing COFs functionalities.

Pristine Metal–Organic Frameworks and their Composites for Renewable Hydrogen Energy Applications

AbstractMetal–organic frameworks (MOFs) have emerged as ideal multifunctional platforms for renewable hydrogen (H2) energy applications owing to their tunable chemical compositions and structures and high porosity. Their advanced component species and porous structure contribute greatly to the enhanced activity, electrical conductivity, photo response, charge‐hole separation efficiency, and structural stability of MOF materials, which are promising for practical H2economy. In this review, we mainly introduce design strategies for the enhancement of electro‐/photochemical behaviors or adsorption performance of porous MOF materials for H2production, storage, and utilization from compositional perspective. Following these engineering strategies, the correlation between composition and property‐structure‐performance of pristine MOFs and their composite with advanced components is illustrated. Finally, challenges and directions of future development of related MOFs and MOF composites for H2economy are provided.

Achieving enhanced microwave absorption performance based on metal/covalent organic frameworks-derived heterostructures

The high performance “thin, light, wide and strong” pursued by microwave absorbing materials is strongly determined by the structure regulation of materials. Herein, we developed the metal/covalent organic frameworks (MOFs/COFs) heterostructures for enabling multiple interfaces and abundant defect vacancies to enhance impedance matching characteristic and dissipation property. The MOF presents uniform pore distribution, large specific surface area and tunable chemical structures. Furthermore, two kinds of COFs were formed by successively polymerizing based on Schiff-base reaction, and in-situ coated on the MOFs-derived Co/C hybrids to favor rich interfaces. The Co/C@TpPa possesses a minimum reflection loss (RLmin) of −48.7 dB at ultrathin thickness of 1.61 mm. In particular, the RLmin of Co/C@TAPB-PDA is −50.6 dB at 8.8 GHz. Meanwhile, CST simulation was carried out to confirm the microwave absorption capabilities under actual far field conditions. The Radar cross section (RCS) values for Co/C@TpPa and Co/C@TAPB-PDA at 0° scattering angle are reduced to 3.88 dB m2 and -12.23 dB m2 from 7.96 dB m2 (Co/C). It is noted that the RCS values of MOFs/COFs-derived hybrids are less than −10 dB m2 at −90°∼90°. This novel MOFs/COFs open up an avenue for advanced absorbing materials.