Metal–Organic Framework (MOF) Derived Electrodes with Robust and Fast Lithium Storage for Li‐Ion Hybrid Capacitors

Hybrid metal–organic frameworks (MOFs) demonstrate great promise as ideal electrode materials for energy‐related applications. Herein, a well‐organized interleaved composite of graphene‐like nanosheets embedded with MnO₂ nanoparticles (MnO₂@C‐NS) using a manganese‐based MOF and employed as a promising anode material for Li‐ion hybrid capacitor (LIHC) is engineered. This unique hybrid architecture shows intriguing electrochemical properties including high reversible specific capacity 1054 mAh g^?1 (close to the theoretical capacity of MnO₂, 1232 mAh g^?1) at 0.1 A g^?1 with remarkable rate capability and cyclic stability (90% over 1000 cycles). Such a remarkable performance may be assigned to the hierarchical porous ultrathin carbon nanosheets and tightly attached MnO₂ nanoparticles, which provide structural stability and low contact resistance during repetitive lithiation/delithiation processes. Moreover, a novel LIHC is assembled using a MnO₂@C‐NS anode and MOF derived ultrathin nanoporous carbon nanosheets (derived from other potassium‐based MOFs) cathode materials. The LIHC full‐cell delivers an ultrahigh specific energy of 166 Wh kg^?1 at 550 W kg^?1 and maintained to 49.2 Wh kg^?1 even at high specific power of 3.5 kW kg^?1 as well as long cycling stability (91% over 5000 cycles). This work opens new opportunities for designing advanced MOF derived electrodes for next‐generation energy storage devices.     

Confined Transformation of Organometal‐Encapsulated MOFs into Spinel CoFe2O4/C Nanocubes for Low‐Temperature Catalytic Oxidation

Development of spinel bimetallic oxides as low‐cost and high‐efficiency catalysts for catalytic oxidation is highly desired. However, rational design of spinel oxides with controlled structure and components still remains a challenge. A general route for large‐scale preparation of spinel CoFe₂O₄/C nanocubes transformed from organometal‐encapsulated metal–organic frameworks (MOFs) via exchange–coordination and pyrolysis combined method is reported. Strong confinement effect between organometallics and MOFs realizes reconstruction of crystal phase and composition, but not simple metallic oxides support by Co²⁺ introduction. Compared with Co₃O₄‐Fe₂O₃/C, MOFs‐derived cubic nano‐CoFe₂O₄/C with higher surface area (115.7 m² g^?1) and favorable surface chemistry exhibits excellent catalytic activity (100% CO conversion at 105 °C) and competitive water‐resisting stability (total conversion at 145 °C for 20 h). Turnover frequency of CoFe₂O₄/C reaches 4.26 × 10^?4 s^?1 at 90 °C, two orders of magnitude higher than commercial Co₃O₄ . Theoretical models show that oxygen vacancies (17.7%) at exposed {112} facet on the carbon interface take superiority in nanocubic spinel phase, which allows reactive species to be strongly adsorbed on nanostructured catalysts' surface and plays key roles in hindering deactivation under moisture rich conditions. The progresses offer a promising way in the development of novel spinel oxides with tailored architecture and properties for vast applications.     

Smart Metal–Organic Frameworks with Reversible Luminescence/Magnetic Switch Behavior for HCl Vapor Detection

Smart luminescent metal–organic frameworks (MOFs) demonstrate promising performance in the detection of toxic gases. The incorporation of twisted or rotary organic ligands with aggregation-induced emission (AIE) characteristics can provide further opportunities in designing such smart MOFs with new topologies and stimuli-responsive behaviors. Herein, novel AIE MOFs are reported with reversible luminescence or a magnetic switch for HCl vapor detection. The twisted conformation of tetrakis(4-carboxyphenyl)ethylene (TCPE) ligand leads to the unique [M⁺–L–M⁻–L–M]_∞ (M = metal clusters, L = ligand) configuration for ZnMOF and CoMOF. Different from conventional MOFs with [M–L]_∞ topology, ZnMOF and CoMOF exhibit a blue-to-yellow greenish fluorescence transition and a ferrimagnetic-to-antiferromagnetic switch behavior, respectively, upon recognition of HCl vapor. The adsorbed HCl molecules rather than coordinated ones are determined to be the main reason, and such luminescence and magnetic switch can be induced in a reversible manner via HCl vapor adsorption/desorption processes with high reliability. This work of AIE MOFs with twisted and rotary ligands shall pave new avenue in design of smart MOFs with new topologies and stimuli-responsive behavior for real-time sensing and detection applications.     

Chemically Resistant,Shapeable, and Conducting Metal‐Organic Gels and Aerogels Built from Dithiooxamidato Ligand

Metal‐organic gels (MOGs) appear as a blooming alternative to well‐known metal‐organic frameworks (MOFs). Porosity of MOGs has a microstructural origin and not strictly crystalline like in MOFs; therefore, gelation may provide porosity to any metal‐organic system, including those with interesting properties but without a porous crystalline structure. The easy and straightforward shaping of MOGs contrasts with the need of binders for MOFs. In this contribution, a series of MOGs based on the assembly of 1D‐coordination polymer nanofibers of formula [M(DTA)]_n (M^II: Ni, Cu, Pd; DTA: dithiooxamidato) are reported, in which properties such as porosity, chemical inertness, mechanical robustness, and stimuli‐responsive electrical conductivity are brought together. The strength of the M? S bond confers an unusual chemical resistance, withstanding exposure to acids, alkalis, and mild oxidizing/reducing chemicals. Supercritical drying of MOGs provides ultralight metal‐organic aerogels (MOAs) with densities as low as 0.03 g cm^?3 and plastic/brittle behavior depending on the nanofiber aspect ratio. Conductivity measurements reveal a semiconducting behavior (10^?12 to 10^?7 S cm^?1 at 298 K) that can be improved by doping (10^?5 S cm^?1). Moreover, it must be stressed that conductivity of MOAs reversibly increases (up to 10^?5 S cm^?1) under the presence of acetic acid.     

Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

A novel hierarchical structured photoanode based on metal–organic frameworks (MOFs)‐derived porous Co₃O₄‐modified TiO₂ nanorod array grown on Si (MOFs‐derived Co₃O₄/TiO₂/Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co₃O₄/TiO₂/Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type‐II heterojunction between TiO₂ and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO₂, the photogenerated electrons from TiO₂ will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO₂ at the TiO₂/Si interface, greatly improving the separation efficiency of photogenerated hole within TiO₂ and enhances the photogenerated electron injection efficiency in Si. While the MOFs‐derived Co₃O₄ obviously improves the optical‐response performance and surface water oxidation kinetics due to the large specific surface area and porous channel structure. Compared with MOFs‐derived Co₃O₄/TiO₂/FTO photoanode, the synergistic function in the MOFs‐derived Co₃O₄/TiO₂/Si NR photoanode brings greatly enhanced photoconversion efficiency of 0.54% (1.04 V vs reversible hydrogen electrode) and photocurrent density of 2.71 mA cm^?2 in alkaline electrolyte. This work provides promising methods for constructing high‐performance PEC water splitting photoanode based on MOFs‐derived materials.     

Porous Metal–Organic Framework@Polymer Beads for Iodine Capture and Recovery Using a Gas‐Sparged Column

Iodine (I₂) capture and recovery is an important process in many industrial practices. Conventional materials for I₂ capture include Ag⁰‐based aerogels and zeolites and C‐based aerogels and powders, which suffer from expensive and/or inefficient recovery. Recently, metal–organic frameworks (MOFs) have shown potential as good adsorbents for I₂ capture with high capacity, fast uptake, and good recyclability. The powder form of MOFs, however, often makes them impractical in large‐scale applications. Herein, a versatile method based on the phase inversion technique is presented to fabricate millimeter‐sized spherical MOF@polymer composite beads, and the use of these beads for I₂ capture and recovery is demonstrated. Besides preserving the crystallinity and pore accessibility of the embedded MOFs in the polymeric matrix, the beads exhibit higher capacity and faster uptake rate for I₂ in both vapor and liquid phases compared to the bulk MOF powder. In order to showcase the applicability of these beads, a gas‐sparged column is used as a proof‐of‐concept device that can efficiently capture and recover more than 99% of I₂ from the feeding solution. The beads can be recycled and reused multiple times, which in combination with their easy handling and storage highlights their superiority compared to MOF powders in adsorption applications.     

Self‐Directed Localization of ZIF‐8 Thin Film Formation by Conversion of ZnO Nanolayers

Control of localized metal–organic framework (MOF) thin film formation is a challenge. Zeolitic imidazolate frameworks (ZIFs) are an important sub‐class of MOFs based on transition metals and imidazolate linkers. Continuous coatings of intergrown ZIF crystals require high rates of heterogeneous nucleation. In this work, substrates coated with zinc oxide layers are used, obtained by atomic layer deposition (ALD) or by magnetron sputtering, to provide the Zn²⁺ ions required for nucleation and localized growth of ZIF‐8 films ([Zn(mim)₂]; Hmim = 2‐methylimidazolate). The obtained ZIF‐8 films reveal the expected microporosity, as deduced from methanol adsorption studies using an environmentally controlled quartz crystal microbalance (QCM) and comparison with bulk ZIF‐8 reference data. The concept is transferable to other MOFs, and is applied to the formation of [Al(OH)(1,4‐ndc)]_n (ndc = naphtalenedicarboxylate) thin films derived from Al₂O₃ nanolayers.     

Preparation and Characterization of Bi-metallic and Tri-metallic Metal Organic Frameworks Based on Trimesic Acid and Co(II), Ni(II), and Cu(II) Ions

Trimesic acid-M1(II):M2(II) (M1,2(II)=M(II)=Co(II), Ni(II) and Cu(II)) bi-metallic or tri-metallic organic frameworks (MOFs) were synthesized by the reaction of trimesic acid (H3BTC) ligand with the corresponding MCl₂nH₂O aqueous solutions. Here, bi- and tri-metallic MOF preparations were demonstrated by using H3BTC as an organic linker, with dual metal ion mixtures at different mole ratios such as Co(II):Ni(II), Ni(II):Cu(II), and Cu(II):Co(II) as metal ion sources in the synthesis of bi-metallic MOFs, and the triple metal ion mixture of Co(II):Ni(II):Cu(II) as the metal ion source in the synthesis of tri-metallic MOFs. The bi- or tri-metallic MOFs were characterized via the Brunauer–Emmett–Teller method, thermogravimetric analyzer (TGA), and magnetic susceptibility measurements with the Gouy method, FT-IR spectroscopy, and electronic spectral studies. The results revealed that the H3BTC MOFs have octahedral and distorted octahedral arrangement around the metal ions, and the d–d transition was not observed in the complex. It was further found that all the prepared MOFs contain water molecules confirmed by Fourier transform infrared (FT-IR) and TGA analyses. The FT-IR spectra of the MOF complexes were characterized by the appearance of a broad band in the region of 3454–3300 cm^?1 due to the ν(-OH) of the coordinated water; therefore, the location of the two water molecules was assumed to be inside the complex structure. Remarkably, the synthesized bi-metallic MOFs had unique and distinct colors depending on the amounts of metal ions used in the feed, implying that these bi-metallic MOFs with tunable M1(II) and M2(II) ratios offer great potential in the design of color-coded materials for use as sensors.     

Dual Sub-Cells Modification Enables High-Efficiency n–i–p Type Monolithic Perovskite/Organic Tandem Solar Cells

Monolithic perovskite/organic tandem solar cells (POTSCs) have attracted increasing attention owing to ability to overcome the Shockley–Queisser limit. However, compromised sub-cells performance limits the tandem device performance, and the power conversion efficiency (PCE) of POTSCs is still lower than their single-junction counterparts. Therefore, optimized sub-cells with minimal energy loss are desired for producing high-efficiency POTSCs. In this study, an ionic liquid, methylammonium acetate (MAAc), is used to modify wide-bandgap perovskite sub-cells (WPSCs), and bathocuproine (BCP) is used to modify small-bandgap organic solar cells. The Ac⁻ group of MAAc can effectively heal the Pb defects in the all-inorganic perovskite film, which enables a high PCE of 17.16% and an open-circuit voltage (V_oc) of 1.31 V for CsPbI_2.2Br_0.8-based WPSCs. Meanwhile, the BCP film, inserted at the ZnO/organic bulk-heterojunction (BHJ) interface, acts as a space layer to prevent direct contact between ZnO and the BHJ while passivating the surface defects of ZnO, thereby mitigating ZnO defect-induced efficiency loss. As a result, PM6:CH1007-based SOSCs exhibit a PCE of 15.46%. Integrating these modified sub-cells enable the fabrication of monolithic n–i–p structured POTSCs with a maximum PCE of 22.43% (21.42% certified), which is one of the highest efficiencies in such type of POTSCs.     

Phthalocyanine‐Based 2D Conjugated Metal‐Organic Framework Nanosheets for High‐Performance Micro‐Supercapacitors

2D conjugated metal‐organic frameworks (2D c‐MOFs) are emerging as a novel class of conductive redox‐active materials for electrochemical energy storage. However, developing 2D c‐MOFs as flexible thin‐film electrodes have been largely limited, due to the lack of capability of solution‐processing and integration into nanodevices arising from the rigid powder samples by solvothermal synthesis. Here, the synthesis of phthalocyanine‐based 2D c‐MOF (Ni₂[CuPc(NH)₈]) nanosheets through ball milling mechanical exfoliation method are reported. The nanosheets feature with average lateral size of ≈160 nm and mean thickness of ≈7 nm (≈10 layers), and exhibit high crystallinity and chemical stability as well as a p‐type semiconducting behavior with mobility of ≈1.5 cm² V^?1 s^?1 at room temperature. Benefiting from the ultrathin feature, the nanosheets allow high utilization of active sites and facile solution‐processability. Thus, micro‐supercapacitor (MSC) devices are fabricated mixing Ni₂[CuPc(NH)₈] nanosheets with exfoliated graphene, which display outstanding cycling stability and a high areal capacitance up to 18.9 mF cm^?2; the performance surpasses most of the reported conducting polymers‐based and 2D materials‐based MSCs.     

Efficient Electron Transfer from an Electron-Reservoir Polyoxometalate to Dual-Metal-Site Metal-Organic Frameworks for Highly Efficient Electroreduction of Nitrogen

Precise design and construction of catalysts with satisfied performance for ambient electrolytic nitrogen reduction reaction (e-NRR) is extremely challenging. By in situ integrating an electron-rich polyoxometalates (POMs) into stable metal organic frameworks (MOFs), five POMs-based MOFs formulated as [Fe_xCo_y(Pbpy)₉(ox)₆(H₂O)₆][P₂W₁₈O₆₂]·3H₂O (abbreviated as Fe_xCo_yMOF-P₂W₁₈) are created and directly used as catalysts for e-NRR. Their electrocatalytic performances are remarkably improved thanks to complementary advantages and promising possibilities of MOFs and POMs. In particular, NH₃ yield rates of 47.04 µg h⁻¹ mg_cat.⁻¹ and Faradaic efficiency of 31.56% by FeCoMOF-P₂W₁₈ for e-NRR are significantly enhanced by a factor of 4 and 3, respectively, compared to the [Fe_0.5Co_0.5(Pbpy)(ox)]₂·(Pbpy)_0.5. The cyclic voltammetry curves, density functional theory calculations and in situ Fourier-transform infrared spectroscopy confirm that there is a directional electron channel from P₂W₁₈ to the MOFs unit to accelerate the transfer of electrons. And the introduction of bimetals Fe and Co in the P₂W₁₈-based MOFs can reduce the energy of the *N₂ to *N₂H step, thereby increasing the production of NH₃. More importantly, this POM in situ embedding strategy can be extended to create other e-NRR catalysts with enhanced performances, which opens a new avenue for future NH₃ production for breakthrough in the bottleneck of e-NRR.     

Novel cathode buffer layer of Ag-doped bathocuproine for small molecule organic solar cell with inverted structure

2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (C₂₆H₂₀N₂), known as bathocuproine (BCP), is a commonly used cathode buffer layer in conventional structure organic solar cells (OSCs). We demonstrated that BCP layer can also be used as a buffer layer in inverted structure OSCs. Unfortunately, the device exhibited an anomalous kink in the current density–voltage (J–V) characteristics, namely, an S-shaped J–V curve, leading to a low fill factor and low power conversion efficiency (PCE). To improve device performance, Ag-doped BCP layer (Ag:BCP) was used to replace the BCP layer. The results showed that the Ag:BCP layer can eliminate the S-kink in the J–V curve, resulting in a large improvement of fill factor and PCE. The origin of the S-shaped J–V curve was demonstrated to originate from the charge accumulation at the fullerene (C₆₀)/BCP interface. On the contrary, the C₆₀/Ag:BCP interface has favorable electronic properties with beneficial gap states for the transport of free carriers. Together with the good conductivity of Ag:BCP layer and the smooth morphology properties, the device performance was greatly improved by Ag:BCP buffer layer.     

Optimization for tandem organic light-emitting diodes based on Firpic

A series of single-unit and tandem blue phosphorescent organic light-emitting diodes (OLEDs) were prepared by adjusting the concentration of dopant based on the structure of ITO/NPB/EL unit/Alq₃/Cs₂CO₃/Al. The results show that tandem device with doping concentration of 10 wt% has appropriate energy transfer, which achieves the best performance with a maximum current efficiency of 3.4 cd·A^?1. Further study found that current efficiency and power efficiency of the tandem OLED adding BCP as hole blocking layer (HBL) can achieve 7.85 cd·A^?1 and 0.72 lm·W^?1, respectively. It is 2.88 times and 1.57 times larger than those of sing-unit devices, and green peak is restrained effectively.     

Mixed-Metal MOF-74 Templated Catalysts for Efficient Carbon Dioxide Capture and Methanation

The vast chemical and structural tunability of metal–organic frameworks (MOFs) are beginning to be harnessed as functional supports for catalytic nanoparticles spanning a range of applications. However, a lack of straightforward methods for producing nanoparticle-encapsulated MOFs as efficient heterogeneous catalysts limits their usage. Herein, a mixed-metal MOF, NiMg-MOF-74, is utilized as a template to disperse small Ni nanoclusters throughout the parent MOF. By exploiting the difference in Ni O and Mg O coordination bond strength, Ni²⁺ is selectively reduced to form highly dispersed Ni nanoclusters constrained by the parent MOF pore diameter, while Mg²⁺ remains coordinated in the framework. By varying the ratio of Ni to Mg in the parent MOF, accessible surface area and crystallinity can be tuned upon thermal treatment, influencing CO₂ adsorption capacity and hydrogenation selectivity. The resulting Ni nanoclusters prove to be an active catalyst for CO₂ methanation and are examined using extended X-ray absorption fine structure and X-ray photoelectron spectroscopy. By preserving a segment of the Mg²⁺-containing MOF framework, the composite system retains a portion of its CO₂ adsorption capacity while continuing to deliver catalytic activity. The approach is thus critical for designing materials that can bridge the gap between carbon capture and CO₂ utilization.     

Disclosing the Role of Defect-Engineered Metal–Organic Frameworks in Mixed Matrix Membranes for Efficient CO2 Separation: A Joint Experimental-Computational Exploration

Incorporation of defects in metal–organic frameworks (MOFs) offers new opportunities for manipulating their microporosity and functionalities. The so-called “defect engineering” has great potential to tailor the mass transport properties in MOF/polymer mixed matrix membranes (MMMs) for challenging separation applications, for example, CO₂ capture. This study first investigates the impact of MOF defects on the membrane properties of the resultant MOF/polymer MMMs for CO₂ separation. Highly porous defect-engineered UiO-66 nanoparticles are successfully synthesized and incorporated into a CO₂-philic crosslinked poly(ethylene glycol) diacrylate (PEGDA) matrix. A thorough joint experimental/simulation characterization reveals that defect-engineered UiO-66/PEGDA MMMs exhibit nearly identical filler–matrix interfacial properties regardless of the defect concentrations of their parental UiO-66 filler. In addition, non-equilibrium molecular dynamics simulations in tandem with gas transport studies disclose that the defects in MOFs provide the MMMs with ultrafast transport pathways mainly governed by diffusivity selectivity. Ultimately, MMMs containing the most defective UiO-66 show the most enhanced CO₂/N₂ separation performance—CO₂ permeability = 470 Barrer (four times higher than pure PEGDA) and maintains CO₂/N₂ selectivity = 41—which overcomes the trade-off limitation in pure polymers. The results emphasize that defect engineering in MOFs would mark a new milestone for the future development of optimized MMMs.     

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

Metal–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 H₂ economy. In this review, we mainly introduce design strategies for the enhancement of electro-/photochemical behaviors or adsorption performance of porous MOF materials for H₂ production, 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 H₂ economy are provided.     

Composite Salt in Porous Metal‐Organic Frameworks for Adsorption Heat Transformation

Adsorptive heat transformation systems such as adsorption thermal batteries and chillers can provide space heating and cooling in a more environmental friendly way. However, their use is still hindered by their relatively poor performances and large sizes due to the limited properties of solid adsorbents. Here, the spray‐drying continuous‐flow synthesis of a new type of solid adsorbents that results from combining metal‐organic frameworks (MOFs), such as UiO‐66, and hygroscopic salts, such as CaCl₂ has been reported. These adsorbents, commonly named as composite salt in porous matrix (CSPM) materials, allow improving the water uptake capabilities of MOFs while preventing their dissolution in the water adsorbed; a common characteristic of these salts due to the deliquescence effect. It is anticipated that MOF‐based CSPMs, in which the percentage of salt can be tuned, are promising candidates for thermal batteries and chillers. In these applications, it is showed that a CSPM made of UiO‐66 and CaCl₂ (38% w/w) exhibits a heat storage capacity of 367 kJ kg^?1 , whereas a second CSPM made of UiO‐66 and CaCl₂ (53% w/w) shows a specific cooling power of 631 W kg^?1 and a coefficient of performance of 0.83, comparable to the best solid adsorbents reported so far.     

A High‐Performance Sodium‐Ion Hybrid Capacitor Constructed by Metal–Organic Framework–Derived Anode and Cathode Materials

Sodium‐ion hybrid capacitors (SIHCs) can potentially combine the virtues of high‐energy density of batteries and high‐power output as well as long cycle life of capacitors in one device. The key point of constructing a high‐performance SIHC is to couple appropriate anode and cathode materials, which can well match in capacity and kinetics behavior simultaneously. In this work, a novel SIHC, coupling a titanium dioxide/carbon nanocomposite (TiO₂/C) anode with a 3D nanoporous carbon cathode, which are both prepared from metal–organic frameworks (MOFs, MIL‐125 (Ti) and ZIF‐8, respectively), is designed and fabricated. The robust architecture and extrinsic pseudocapacitance of TiO₂/C nanocomposite contribute to the excellent cyclic stability and rate capability in half‐cell. Hierarchical 3D nanoporous carbon displays superior capacity and rate performance. Benefiting from the merits of structures and performances of anode and cathode materials, the as‐built SIHC achieves a high energy density of 142.7 W h kg^?1 and a high power output of 25 kW kg^?1 within 1–4 V, as well as an outstanding life span of 10 000 cycles with over 90% of the capacity retention. The results make it competitive in high energy and power–required electricity storage applications.     

New-Generation Anion-Pillared Metal–Organic Frameworks with Customized Cages for Highly Efficient CO2 Capture

The rational design of porous materials for CO₂ capture under realistic process conditions is highly desirable. However, trade-offs exist among a nanopore's capacity, selectivity, adsorption heat, and stability. In this study, a new generation of anion-pillared metal-organic frameworks (MOFs) are reported with customizable cages for benchmark CO₂ capture from flue gas. The optimally designed TIFSIX-Cu-TPA exhibits a high CO₂ capacity, excellent CO₂/N₂ selectivity, high thermal stability, and chemical stability in acid solution and acidic atmosphere, as well as modest adsorption heat for facile regeneration. Additionally, the practical separation performance of the synthesized MOFs is demonstrated by breakthrough experiments under various process conditions. A highly selective separation is achieved at 298–348 K with the impressive CO₂ capacity of 2.1–1.4 mmol g⁻¹. Importantly, the outstanding performance is sustained under high humidity and over ten repeat process cycles. The molecular mechanism of MOF's CO₂ adsorption is further investigated in situ by CO₂ dosed single crystal structure and theoretical calculations, highlighting two separate binding sites for CO₂ in small and large cages featured with high CO₂ selectivity and loading, respectively. The simultaneous adsorption of CO₂ inside these two types of interconnected cages accounts for the high performance of these newly designed anionic pillar-caged MOFs.     

Engineering Fe–Fe3C@Fe–N–C Active Sites and Hybrid Structures from Dual Metal–Organic Frameworks for Oxygen Reduction Reaction in H2–O2 Fuel Cell and Li–O2 Battery

Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe₃C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction reaction (ORR) electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe₃C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm^?2 in peak power density) and an aprotic Li–O₂ battery (8749 mAh g^?1 in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe₃C contribution to the catalyst performance, suggesting Fe₃C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.