Conjugated polymeric molecules have been heralded as promising electrode materials for the next-generation energy-storage technologies owing to their chemical flexibility at the molecular level, environmental benefit, and cost advantage. However, before any practical implementation takes place, the low capacity, poor structural stability, and sluggish ion/electron diffusion kinetics remain the obstacles that have to be overcome. Here, we report the synthesis of a few-layered two-dimensional covalent organic framework trapped by carbon nanotubes as the anode of lithium-ion batteries. Remarkably, upon activation, this organic electrode delivers a large reversible capacity of 1536 mAh g −1 and can sustain 500 cycles at 100 mA g −1 . Aided by theoretical calculations and electrochemical probing of the electrochemical behavior at different stages of cycling, the storage mechanism is revealed to be governed by 14-electron redox chemistry for a covalent organic framework monomer with one lithium ion per C=N group and six lithium ions per benzene ring. This work may pave the way to the development of high-capacity electrodes for organic rechargeable batteries.

Covalent organic frameworks (COFs) with reversible redox behaviors are potential electrode materials for lithium‐ion batteries (LIBs). However, the sluggish lithium diffusion kinetics, poor electronic conductivity, low reversible capacities, and poor rate performance for most reported COF materials limit their further application. Herein, a new 2D COF (TFPB‐COF) with six unsaturated benzene rings per repeating unit and ordered mesoporous pores (≈2.1 nm) is designed. A chemical stripping strategy is developed to obtain exfoliated few‐layered COF nanosheets (E‐TFPB‐COF), whose restacking is prevented by the in situ formed MnO2 nanoparticles. Compared with the bulk TFPB‐COF, the exfoliated TFPB‐COF exhibits new active Li‐storage sites associated with conjugated aromatic π electrons by facilitating faster ion/electron kinetics. The E‐TFPB‐COF/MnO2 and E‐TFPB‐COF electrodes exhibit large reversible capacities of 1359 and 968 mAh g−1 after 300 cycles with good high‐rate capability.

Organic electrodes for low-cost potassium ion batteries (PIBs) are attracting more interest by virtue of their molecular diversity, environmental friendliness, and operation safety. But the sluggish potassium diffusion kinetics, dissolution in organic electrolyte, poor electronic conductivity, and low reversible capacities are several drawbacks compared with inorganic counterparts. Herein, the boronic ester based covalent organic framework (COF) material is successfully prepared on the exterior surface of carbon nanotubes (CNTs) via rational design of the organic condensation reaction and used as an anode material for PIBs. The few-layered structure of COF-10@CNT can provide more exposed active sites and fast K + kinetics. It exhibits ultrahigh potassium storage performances (large reversible capacities of 288 mAh g −1 after 500 cycles at 0.1 A g −1 and 161 mAh g −1 after 4000 cycles at 1 A g −1 ), which is superior to previous organic electrodes and most inorganic electrodes. Moreover, the K-storage mechanism is proposed to be π-cation interaction between K + and conjugated πelectrons of benzene rings.

A unique CuO@NiO microsphere with three-layer ball-in-ball hollow morphology is successfully synthesized by Cu-Ni bimetallic organic frameworks. The beforehand facile microwave-assisted production of the Ni organic framework sphere is used as the template to induce the morphology control of bimetallic oxides. Designed by the controlled surface cationic exchange reactions between Cu and Ni ions, there is an elemental gradient (decreased amount of CuO but increased amount of NiO) from the shell to the core of the microsphere product. This ternary metal oxide hollow structure is found to be very suitable for solving the critical volume expansion problem, which is critical for all high-capacity metal oxide electrodes for lithium ion batteries. A reversible larger-than-theoretical capacity of 1061 mAh·g(-1) can be retained after a repetitive 200 cycles without capacity fading compared to the initial cycle. These excellent electrochemical properties are ascribed to the step-by-step lithium insertion reactions induced by the matched CuO@NiO composition from the shell to the core and facilitated lithium/electron diffusion and accommodated volume change in the porous bimetallic oxides microsphere with a multiple-layer yolk-shell nanostructure.

In order to fulfill the increasing demand for renewable energy, besides the lithium-ion batteries, other alkali (Na, K)-ion batteries are extensively investigated. However, the difficulty to find universal and environmentally benign electrodes for these alkali (Na, K)-ion batteries still severely restricts their development. Promising characteristics, including molecular diversity, low cost, and operation safety, endow the organic electrodes more advantages for applications in alkali-ion batteries. However, organic electrodes usually deliver a reversible capacity smaller than that of their inorganic counterparts due to sluggish ion/electron diffusion and possible dissolution in organic electrolytes. This work introduces fluorine atoms into the covalent triazine frameworks (CTF) to obtain two-dimensional layered fluorinated CTF (FCTF) and its exfoliated few-layered product (E-FCTF) and uses them as anodes of Li, Na, and K organic batteries. Exfoliated E-FCTF electrode delivers high reversible capacities, as well as excellent cycle life for alkali organic batteries (1035 mAh g −1 at 100 mA g −1 after 300 cycles and 581 mAh g −1 at 2 A g −1 after 1000 cycles for lithium organic batteries). In view of the experimental probing and the theoretical calculation, the Li storage mechanism for the E-FCTF can be determined to be an intriguing multielectronic redox reaction originated from lithium storage on the benzene ring and triazine ring units.

The development of the next‐generation lithium ion battery requires environmental‐friendly electrode materials with long cycle life and high energy density. Organic compounds are a promising potential source of electrode materials for lithium ion batteries due to their advantages of chemical richness at the molecular level, cost benefit, and environmental friendliness, but they suffer from low capacity and dissatisfactory cycle life mainly due to hydrophobic dissolution in organic electrolytes and poor electronic conductivity. In this work, two types of triazine‐based covalent organic nanosheets (CONs) are exfoliated and composited with carbon nanotubes. The thin‐layered 2D structure for the exfoliated CONs can activate more functional groups for lithium storage and boost the utilization efficiency of redox sites compared to its bulk counterpart. Large reversible capacities of above 1000 mAh g−1 can be achieved after 250 cycles, which is comparable to high‐capacity inorganic electrodes. Moreover, the lithium‐storage mechanism is determined to be an intriguing 11 and 16 electron redox reaction, associated with the organic groups (unusual triazine ring, piperazine ring, and benzene ring, and common CN, NH groups).

The metal-organic-framework (MOF) approach is demonstrated as an effective strategy for the morphology evolution control of MIL-53(Fe) with assistance of microwave irradiation. Owing to the homogeneous nucleation offered by microwave irradiation and confined porosity and skeleton by MOF templates, various porous FeO nanostructures including spindle, concave octahedron, solid octahedron, yolk-shell octahedron, and nanorod with porosity control are derived by simply adjusting the irradiation time. The formation mechanism for the MOF precursors and their derived iron oxides with morphology control is investigated. The main product of the mesoporous yolk-shell octahedron-in-octahedron FeO nanostructure is also found to be a promising anode material for lithium-ion batteries due to its excellent Li-storage performance. It can deliver a reversible larger-than-theoretical capacity of 1176 mAh g after 200 cycles at 100 mA g and good high-rate performance (744 mAh g after 500 cycles at 1 A g).

units, SBUs) and coordinated organic ligands via the more flexible coordination bonds, which results in the controllable morphology and pore characteristic. [1f,g] Induced by these structural merits, COF and MOF have been widely applied in gas storage/separation, catalysis, and photoelectric conversion, and even the field of energy storage including Li-ion batteries, supercapacitors, and hydrogen storage. [2] In order to effectively combine the merits of COF and MOF and acquire the maximized performances, there are few recent reports regarding the hybridization of COF and MOF. [3] By introducing the as-prepared MOF into the synthetic process of COF, MOF@COF core-shell [3a,b] or MOF-coated COF [3c] hybrids were obtained. All these hybrids have been demonstrated with excellent photocatalytic performances as the effective photocatalysts/photocatalysis platforms for degradation of rhodamine B, [3a] dehydrogenation of ammonia borane, [3b] and H 2 evolution, [3c] respectively. This kind of approach (introducing the as-prepared MOF into the synthetic process of COF) would result in the comparatively simple combination of COF and MOF with core-shell or coating composite mode (no principal morphology change), and the molecular-level interlinked hybridization between COF and MOF remains unexplored.For the purpose of property optimization, intimate hybridization between two components is highly desirable, which may lead to further morphology adjustment, and consequent performance improvement. Considering the fact that organic groups from COF may also coordinate with metal ions of MOF, we design a COF/Mn-MOF hybrid structure with flower-like morphology, which is different from pristine COF or Mn-MOF. A strong synergistic effect relative to new active sites from MOF and COF for lithium storage is observed in the composite. Hollow or coreshell microspheres of MnS@N/S codoped carbon can also be derived with superior electrochemical properties.The COF/Mn-MOF composite with benchmarked pristine COF or Mn-MOF ( Figure S1a,b, Supporting Information) was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman and 13 C nuclear magnetism measurements in Figure S2a-d (Supporting Information). All characteristic diffraction peaks for Mn-MOF [4] can be detected for COF/ Mn-MOF with clear shift to small angle for its two main peaks (2θ ≈ 10.5° and ≈21.7°), which is probably originated from the Covalent organic frameworks (COF) or metal-organic frameworks have attracted significant attention for various applications due to their intriguing tunable micro/mesopores and composition/functionality control. Herein, a coordination-induced interlinked hybrid of imine-based covalent organic frameworks and Mn-based metal-organic frameworks (COF/Mn-MOF) based on the MnN bond is reported. The effective molecular-level coordinationinduced compositing of COF and MOF endows the hybrid with unique flower-like microsphere morphology and superior lithium-storage performances that originate from activated Mn centers an...