aromatic groups, which via columnar π-π stacking order into a periodic 3D structure (Scheme S1, Supporting Information). Their modular construct and ordered porosity makes them find use in diverse applications Here we are seeking application of 2D COFs in metal-ion batteries, which are typically made of electrodes with layered structures, for example, graphite as anode and LiCoO 2 as cathode. Owing to their graphite resembling structure, COF can serve as anode. Since their initial discovery, many 2D materials with comparable layered structures have been explored as lithium insertion-deinsertion materials. [28][29][30][31][32][33][34][35][36][37][38][39] Some of the highly desirable characteristics of a superior anode material include moderate to high surface accessibility to ensure maximum charge storage per unit area, and the other is the hierarchical porosity for favorable kinetics. Exfoliation enhances surface accessibility and active site creation in such 2D materials. [40][41][42][43][44][45][46][47][48] In this regard, COFs could have much more to offer. [49][50][51] Exfoliation in any 2D material is largely dependent on the interlayer forces holding them. Typically, the COF layers are held together by interlayer π-π interactions or in some cases via additional hydrogen bonding. [52,53] However, unlike graphite, the layers of COF are not built from fused aromatic rings. In their optimized Covalent organic framework (COF) can grow into self-exfoliated nanosheets. Their graphene/graphite resembling microtexture and nanostructure suits electrochemical applications. Here, covalent organic nanosheets (CON) with nanopores lined with triazole and phloroglucinol units, neither of which binds lithium strongly, and its potential as an anode in Li-ion battery are presented. Their fibrous texture enables facile amalgamation as a coin-cell anode, which exhibits exceptionally high specific capacity of ≈720 mA h g −1 (@100 mA g −1 ). Its capacity is retained even after 1000 cycles. Increasing the current density from 100 mA g −1 to 1 A g −1 causes the specific capacity to drop only by 20%, which is the lowest among all high-performing anodic COFs. The majority of the lithium insertion follows an ultrafast diffusion-controlled intercalation (diffusion coefficient, D Li + = 5.48 × 10 −11 cm 2 s −1 ). The absence of strong Liframework bonds in the density functional theory (DFT) optimized structure supports this reversible intercalation. The discrete monomer of the CON shows a specific capacity of only 140 mA h g −1 @50 mA g −1 and no sign of lithium intercalation reveals the crucial role played by the polymeric structure of the CON in this intercalation-assisted conductivity. The potentials mapped using DFT suggest a substantial electronic driving-force for the lithium intercalation. The findings underscore the potential of the designer CON as anode material for Li-ion batteries. Lithium Storage

The ordered modular structure of a covalent organic framework (COF) facilitates the selective incorporation of electronically active segments that can be tuned to function cooperatively. This designability inspires developing COFbased single-source white light emitters, required in nextgeneration solid-state lighting. Here, we present a new anthracene-resorcinol-based COF exhibiting white light emission. The keto−enol tautomers present in the COF give rise to dual emission, which can be tuned by the O-donor and Ndonor solvents. Importantly, when suspended in a solid polymer matrix, this dual emission is retained as both tautomers coexist. A mere 0.32 wt % loading of the COF in poly(methyl methacrylate) (PMMA) gives a solvent-free film with intense white light emission (CIE coordinates (0.35, 0.36)). From steady-state and time-resolved studies, the mechanism of the white light emission has been unambiguously assigned to fluorescence, with the blue emission originating from the π-stacked columns of anthracene, and the mixture of red and green from the keto−enol tautomerized resorcinol units. The study introduces the COF as a new class of readily processable, single-source white light emitter.

Dithiine linkage formation via a dynamic and self-correcting nucleophilic aromatic substitution reaction enables the de novo synthesis of a porous thianthrene-based two-dimensional covalent organic framework (COF). For the first time, this organo-sulfur moiety is integrated as a structural building block into a crystalline layered COF. The structure of the new material deviates from the typical planar interlayer π-stacking of the COF to form undulated layers caused by bending along the C–S–C bridge, without loss of aromaticity and crystallinity of the overall COF structure. Comprehensive experimental and theoretical investigations of the COF and a model compound, featuring the thianthrene moiety, suggest partial delocalization of sulfur lone pair electrons over the aromatic backbone of the COF decreasing the band gap and promoting redox activity. Postsynthetic sulfurization allows for direct covalent attachment of polysulfides to the carbon backbone of the framework to afford a molecular-designed cathode material for lithium–sulfur (Li–S) batteries with a minimized polysulfide shuttle. The fabricated coin cell delivers nearly 77% of the initial capacity even after 500 charge–discharge cycles at 500 mA/g current density. This novel sulfur linkage in COF chemistry is an ideal structural motif for designing model materials for studying advanced electrode materials for Li–S batteries on a molecular level.

A covalent organic framework (COF), built from light atoms with a graphitic structure, could be an excellent anodic candidate for lightweight batteries, which can be of use in portable devices. But to replace the commercial graphite anode, they need more Li‐interactive sites/unit‐cell and all such sites should be made to participate. The compromise made in the volumetric density to gain the gravimetric advantage should be minimal. Exfoliation enhances surface/functional group accessibility yielding high capacity and rapid charge storage. A chemical strategy for simultaneous exfoliation and increase of Li‐loving active‐pockets can deliver a lightweight Li‐ion battery (LIB). Here, anthracene‐based COFs are chemically exfoliated into few‐layer‐thick nanosheets using maleic anhydride as a functionalizing exfoliation agent. It not only exfoliates but also introduces multiple Li‐interactive carbonyl groups, leading to a loading of 30 Li/unit‐cell (vs one Li per C6). The exfoliation enhances the specific capacity by ≈4 times (200–790 mAh g−1 @100 mA g−1). A realistic full‐cell, made using the exfoliated COF against a LiCoO2 cathode, delivers a specific capacity of 220 mAh g−1 over 200 cycles. The observed capacity stands highest among all organic polymers. For the first report of a COF derived full‐cell LIB, this is a windfall.

Covalent organic frameworks (COFs), because of their ordered pores and crystalline structure, become designable polymers for charge storage applications. Supercapacitors are critical in developing hybrid energy devices. Amalgamating these high-surface-area frameworks in the capacitor assembly can aid develop robust solid-state supercapacitors. Here, we present supercapacitors drawn on three closely related pyridyl-hydroxyl functionalized COFs. The keto-enol tautomerism and the hydrogen bonding ability of the hydroxyl units promise added chemical stability in this potentially hydrolyzable Schiff-bonded COF. Meanwhile, the pyridyl and triazine groups ensure rapid charge storage by reversibly interacting with protons from the acidic electrolyte. The COF with the highest surface area, as expected, yields an excellent specific capacitance of 546 F/g at 500 mA/g in acidic solution and ∼92 mF/cm2 at 0.5 mA/cm2 in the solid-state device, which is the highest among all the COF-derived solid-state capacitors, which is reflected by a high power density of 98 μW/cm2 at 0.5 mA/cm2, most of which is retained even after 10 000 cycles. This high activity comes from a smooth electrical-double-layer-capacitance favored by an ordered-porous structure and some pseudo-capacitance assisted by the participation of redox-active functional groups. The study highlights the by-design development of COFs for superior energy/charge devices.

Lowering the LUMO levels of an anodic COF through the incorporation of N-rich modules favors electron accumulation on it, which sets up an electronic drive for the Na⁺ ions to enter the anode from the electrolyte. The optimal framework⋯Na⁺ interactions delivers excellent rate-performance.

Covalent organic frameworks (COFs) are a new class of porous crystalline polymers with a modular construct that favors functionalization. COF pores can be used to grow nanoparticles (nPs) with dramatic size reduction, stabilize them as dispersions, and provide excellent nP access. Embedding substrate binding sites in COFs can generate host–guest synergy, leading to enhanced catalytic activity. In this report, Cu/Cu2O nPs (2–3 nm) are grown on a COF, which is built by linking a phenolic trialdehyde and a triamine through Schiff bonds. Their micropores restrict the nP to exceptionally small sizes (∼2–3 nm), and the pore walls decorated with strategically positioned hydrogen-bonding phenolic groups anchor the substrates via hydrogen-bonding, whereas the basic pyridyl sites serve as cationic species to stabilize the [CuclusterCl2]2– type reactive intermediates. This composite catalyst shows high activity for Glaser–Hay heterocoupling reactions, an essential 1,3-diyne yielding reaction with widespread applicability in organic synthesis and material science. Despite their broad successes in homocoupled products, preparation of unsymmetrical 1,3-diynes is challenging due to poor selectivity. Here, our COF-based Cu catalyst shows elevated selectivity toward heterocoupling product(s) (Cu nP loading 0.0992 mol %; turn over frequency: ∼45–50; turn over number: ∼175–190). The reversible redox activity at the Cu centers has been demonstrated by carrying out X-ray photoelectron spectroscopy on the frozen reactions, whereas the crucial interactions between the substrates and the binding sites in their optimized configurations have been modeled using density functional theory methods. This report emphasizes the utility of COFs in developing a heterogeneous catalyst for a truly challenging organic heterocoupling reaction.

Redox‐active covalent organic frameworks (COFs) store charges but possess inadequate electronic conductivity. Their capacitive action works by storing H+ ions in an acidic electrolyte and is typically confined to a small voltage window (0–1 V). Increasing this window means higher energy and power density, but this risks COF stability. Advantageously, COF's large pores allow the storage of polarizable bulky ions under a wider voltage thus reaching higher energy density. Here, a COF–electrode–electrolyte system operating at a high voltage regime without any conducting carbon or redox active oxides is presented. Conducting polypyrrole (Ppy) chains are synthesized within a polyimide COF to gain electronic conductivity (≈10 000‐fold). A carbon‐free quasi‐solid‐state capacitor assembled using this composite showcases high pseudo‐capacitance (358 mF cm−2@1 mA cm−2) in an aqueous gel electrolyte. The synergy among the redox‐active polyimide COF, polypyrrole and organic electrolytes allows a wide‐voltage window (0–2.5 V) leading to high energy (145 μWh cm−2) and power densities (4509 μW cm−2). Amalgamating the polyimide‐COF and the polypyrrole as one material minimizes the charge and mass transport resistances. Computation and experiments reveal that even a partial translation of the modules/monomers intrinsic electronics to the COF imparts excellent electrochemical activity. The findings unveil COF‐confined polymers as carbon‐free energy storage materials.