Stabilizing Redox-Active Hexaazatriphenylene in a 2D Conductive Metal–Organic Framework for Improved Lithium Storage Performance

Organic redox-active materials are promising electrode candidates for lithium-ion batteries by virtue of their designable structure and cost-effectiveness. However, their poor electrical conductivity and high solubility in organic electrolytes limit the device's performance and practical applications. Herein, the π-conjugated nitrogen-containing heteroaromatic molecule hexaazatriphenylene (HATN) is strategically embedded with redox-active centers in the skeleton of a Cu-based 2D conductive metal–organic framework (2D c-MOF) to optimize the lithium (Li) storage performance of organic electrodes, which delivers improved specific capacity (763 mAh g⁻¹ at 300 mA g⁻¹), long-term cycling stability (≈90% capacity retention after 600 cycles at 300 mA g⁻¹), and excellent rate performance. The correlation of experimental and computational results confirms that this high Li storage performance derives from the maximum number of active sites (CN sites in the HATN unit and CO sites in the CuO₄ unit), favorable electrical conductivity, and efficient mass transfer channels. This strategy of integrating multiple redox-active moieties into the 2D c-MOF opens up a new avenue for the design of high-performance electrode materials.     

A Conductive 2D Conjugated Tetrathia[8]circulene-Based Nickel Metal–Organic Framework for Energy Storage

Herein, a novel D₄ symmetrical redox-active ligand tetrathia[8]circulene-2,3,5,6,8,9,11,12-octaol (8OH-TTC) is designed and synthesized, which coordinates with Ni²⁺ ions to construct a 2D conductive metal-organic framework (2D c-MOF) named Ni-TTC. Ni-TTC exhibits typical semiconducting properties with electrical conductivity up to ≈1.0 S m⁻¹ at 298 K. Furthermore, magnetism measurements show the paramagnetic property of Ni-TTC with strong antiferromagnetic coupling due to the presence of semiquinone ligand radicals and Ni²⁺ sites. In virtue of its decent electrical conductivity and good redox activity, the gravimetric capacitance of Ni-TTC is up to 249 F g⁻¹ at a discharge rate of 0.2 A g⁻¹, which demonstrates the potential of tetrathia[8]circulene-based redox-active 2D c-MOFs in energy storage applications.     

Self-Standing Covalent Organic Framework Membranes for H2/CO2 Separation

Covalent organic frameworks (COFs) are proposed as promising candidates for engineering advanced molecular sieving membranes due to their precise pore sizes, modifiable pore environment, and superior stability. However, COFs are insoluble in common solvents and do not melt at high temperatures, which presents a great challenge for the fabrication of COF-based membranes (COFMs). Herein, for the first time, a new synthetic strategy is reported to prepare continuous and intact self-standing COFMs, including 2D N-COF membrane and 3D COF-300 membrane. Both COFMs show excellent selectivity of H₂/CO₂ mixed gas (13.8 for N-COF membrane and 11 for COF-300 membrane), and especially ultrahigh H₂ permeance (4319 GPU for N-COF membrane and 5160 GPU for COF-300 membrane), which is superior to those of COFMs reported so far. It should be noted that the overall separation performance of self-standing COFMs exceeds the Robeson upper bound. Furthermore, a theoretical study based on Grand Canonical Monte Carlo (GCMC) simulation is performed to explain the excellent separation of H₂/CO₂ through COFMs. Thus, this facile preparation method will provide a broad prospect for the development of self-standing COFMs with highly efficient H₂ purification.     

Exploring a Stable and Dense 3D Lead Chloride Hybrid with Emission of Self-Trapped Excitons toward X-Ray Scintillation

The exceptional photophysical properties of 3D organic–inorganic lead halide hybrids (OILHs) endow their significant potential for usage in optoelectronics, which has sparked intense research on novel 3D OILHs and associated applications. However, constructing new 3D OILHs based on large organic cations suffers from tough challenges due to the limitation of the Goldschmidt tolerance factor rule, let alone further explorations of their practical applications. Herein, a brand-new 3D lead chloride hybrid, (1MPZ)Pb₄Cl₁₀·H₂O ( 1 , 1MPZ = 1-methylpiperazine) is reported, featuring a dense 3D lead chloride framework made of the corner-, edge-, and face-shared lead chloride polyhedra. 1 presents a broadband white light emission with a large Stokes shift and a nanosecond photoluminescence lifetime, which originates from radiative recombination of self-trapped excitons (STEs) induced by the highly distorted structure. Such a reabsorption-free and fast-decayed STEs emission coupling with the dense 3D architecture further enables 1 with effective X-ray scintillation with good sensitivity. Impressively, 1 also shows superior environmental and radiation stability. This study provides a new 3D OILH with appealing luminescence, not only expanding the 3D OILH family but also inspiring the exploitation of their optoelectronic applications.     

Biomolecules-Incorporated Metal-Organic Frameworks Gated Light-Sensitive Organic Photoelectrochemical Transistor for Biodetection

Incorporating biomolecules into metal-organic frameworks (MOFs) as exoskeletons to form biomolecules-MOFs biohybrids has attracted great attention as an emerging class of advanced materials. Organic devices have been shown as powerful platforms for next-generation bioelectronics, such as wearable biosensors, tissue engineering constructs, and neural interfaces. Herein, biomolecules-incorporated MOFs as innovative gating module is realized for the first time, which is exemplified by biocatalytic precipitation (BCP)-oriented horseradish peroxidase (HRP)-embedded zeolitic imidazolate framework-90 (HRP@ZIF-90)/CdIn₂S₄ gated organic photoelectrochemical transistor under light illumination. In connection to a sandwich immunocomplexing targeting the model analyte human IgG, the IgG-dependent generation of H₂O₂ and the tandem HRP-triggered BCP reaction can cause the in situ blocking of the pore network of ZIF-90, leading to variant gating effect with corresponding responses of the device. This representative biodetection achieved good analytical performance with a wide linear range and a low detection limit of 100 fg mL⁻¹. In the view of the plentiful biomolecule-MOF complexes and their potential interactions with organic systems, this study provides a proof-of-concept study for the generic development of biomolecules-MOFs-gated electronics and beyond.     

In Situ Deformation Topology of COFs with Shortened Channels and High Redox Properties for Li–S Batteries

Covalent organic frameworks (COFs) with various topologies are typically synthesized by selecting and designing connecting units with rich shapes. However, this process is time-consuming and labour-intensive. Besides, the tight stacking of COFs layers greatly restrict their structural advantages. It is crucial to effectively exploit the high porosity and active sites of COFs by topological design. Herein, for the first time, inducing in situ topological changes in sub-chemometric COFs by adding graphene oxide (GO) without replacing the monomer, is proposed. Surprisingly, GO can slow down the intermolecular stacking and induce rearrangement of COFs nanosheets. The channels of D- [4+3] COFs are significantly altered while the stacking of periodically expanded framework is weakened. This not only maximizes the exposure of pore area and polar groups, but also shortens the channels and increases the redox activity, which enables high loading while enhancing host-guest interactions. This topological transformation to exhibit the structural features of COFs for efficient application is an innovative molecular design strategy.     

Hybrid Catalyst Coupling Zn Single Atoms and CuNx Clusters for Synergetic Catalytic Reduction of CO2

Reverse water-gas shift (RWGS) reaction is the initial and necessary step of CO₂ hydrogenation to high value-added products, and regulating the selectivity of CO is still a fundamental challenge. In the present study, an efficient catalyst (CuZnN_x@C-N) composed by Zn single atoms and Cu clusters stabilized by nitrogen sites is reported. It contains saturated four-coordinate Zn-N₄ sites and low valence CuN_x clusters. Monodisperse Zn induces the aggregation of pyridinic N to form Zn-N₄ and N₄ structures, which show strong Lewis basicity and has strong adsorption for *CO₂ and *COOH intermediates, but weak adsorption for *CO, thus greatly improves the CO₂ conversion and CO selectivity. The catalyst calcined at 700 °C exhibits the highest CO₂ conversion of 43.6% under atmospheric pressure, which is 18.33 times of Cu-ZnO and close to the thermodynamic equilibrium conversion rate (49.9%) of CO₂. In the catalytic process, CuN_x not only adsorbs and activates H₂, but also cooperates with the adjacent Zn-N₄ and N₄ structures to jointly activate CO₂ molecules and further promotes the hydrogenation of CO₂. This synergistic mechanism will provide new insights for developing efficient hydrogenation catalysts.     

Glyphosate Adsorption from Water Using Hierarchically Porous Metal–Organic Frameworks

The selective removal of one ligand in mixed-ligand MOFs upon thermolysis provides a powerful strategy to introduce additional mesopores without affecting the overall MOF structure. By varying the initial ligand ratio, MOFs of the MIL-125-Ti family with two distinct hierarchical pore architectures are synthesized, resembling either large cavities or branching fractures. The performance of the resulting hierarchically porous MOFs is evaluated toward the adsorptive removal of glyphosate (N-(phosphonomethyl)glycine) from water, and the adsorption kinetics and mechanism are examined. Due to their strong affinity for phosphoric groups, the numerous Ti–OH groups resulting from the selective ligand removal act as natural anchor points for effective glyphosate uptake. The relationships between contact duration, glyphosate concentration, and adsorbent dosage are investigated, and the impact of these parameters on the effectiveness of glyphosate removal from contaminated water samples is examined. The introduction of additional mesopores has increased the adsorption capacities by nearly 3 times with record values exceeding 440.9 mg g⁻¹, which ranks these MOFs among the best-reported adsorbents.     

Imaging Solvent-Triggered Gaseous Iodine Uptake on Single Covalent Organic Frameworks

Covalent organic frameworks (COFs) are promising solid absorbents for the treatment of gaseous iodine. However, extensive efforts are still focused on empirical optimizations of specific binding sites and pore structures in COFs, and the chemical control of gaseous iodine uptake on COFs remains challenging. In this study, the chemically triggered sorption properties of COF-300 for I₂ vapors at the single-particle level with the dark-field microscope (DFM) are explored. The present operando single-particle DFM imaging method enables the direct visualization of an adsorption activity transformation from inactive COF-300 to active solvated COF-300 toward gaseous I₂ vapors. Exploiting the useful reaction information from time-lapsed DFM images, the tunable adsorption performance of solvated COF-300 is quantitatively compared by various solvents. The results illustrate that the isopropanol (IPA)-solvated COF-300 achieves the optimum adsorption capacity for I₂ among the absorbents. The reaction mechanism is elucidated to be the channel size enlargement and modification of internal surface chemistry in the IPA-solvated COF-300, producing a stable I₂/IPA-solvated COF-300 complex after the sorption reaction. The present chemical control of the sorption behavior of COF-300 revealed by DFM opens up a new fundamental paradigm for rationally developing high-performance COF-based absorbents for removing I₂ vapors.