Redox-Active Covalent Organic Frameworks with Nickel–Bis(dithiolene) Units as Guiding Layers for High-Performance Lithium Metal Batteries

Abstract

Combining the chemistry of metal−organic frameworks (MOFs) and covalent organic frameworks (COFs) can bring new opportunities for the design of advanced materials with enhanced tunability and functionality. Herein, we constructed two COFs based on Ni−bis(dithiolene) units and imine bonds, representing a bridge between traditional MOFs and COFs. The Ni− bis(dithiolene)tetrabenzaldehyde as the 4-connected linker was initially synthesized, which was further linked by 4-connected tetra(aminophenyl)pyrene (TAP) or 3connected tris(aminophenyl)amine (TAA) linkers into two COFs, namely, Ni-TAP and Ni-TAA. Ni-TAP shows a two-dimensional sql network, while TAA is a twofold interpenetrated framework with an ffc topology. They both exhibit a high Brunauer−Emmett−Teller surface area (324 and 689 m 2 g −1 for Ni-TAP and Ni-TAA, respectively), a fairly good conductivity (1.57 × 10 −6 and 9.75 × 10 −5 S m −1 for Ni-TAP and Ni-TAA, respectively), and high chemical stability (a stable pH window of 1−14 for Ni-TAA). When applied in lithium metal batteries as an intermediate layer for guiding the uniform Li electrodeposition, Ni-TAP and Ni-TAA displayed impressive lithiophilicity and high Li-ion conductivity, enabling the achievement of smooth and dense Li deposition with a clear columnar morphology and stable Li plating/stripping behaviors with high Li utilization, which is anticipated to pave the way to upgrade Li metal anodes for application in high-energy-density battery systems.

Covalent organic frameworks with Ni-Bis(dithiolene) and Co-porphyrin units as bifunctional catalysts for Li-O 2 batteries

“…Design and synthesis of bimetallic co/Ni-COF Ni-bis(dithiolene) can be regarded as an inorganic analog of TTF (32). Therefore, the structures of TTF-COFs provide a blueprint for the design of bimetallic Co/Ni-COFs.…”

Three-dimensional porphyrin-based covalent organic frameworks withstptopology for an efficient electrocatalytic oxygen evolution reaction

“…[20][21][22] For example, metal single-site catalytic arrays can be realized by presetting metal chelation sites on the backbone of COFs via the imine bonds and vicinal functional groups or by using polydentate building units directly. [23][24][25][26][27][28] Particularly, as an attractive planar semiconducting ligand, porphyrins can provide a strict and stable tetracoordinate environment (M-N 4 ) for a variety of transition metals. 29 The exposed axial unoccupied position of the metal atom in metalloporphyrins represents an ideal redox active site for the catalytic process of multiple electron transfer, 30,31 making metalloporphyrin-based materials promising catalysts for a large variety of transformations.…”

Phenanthroimidazole-Based Covalent Organic Frameworks with Enhanced Activity for the Photocatalytic Hydrogen Evolution Reaction

“…The photocatalytic potential of COFs has already been reported. − The highly crystalline nature of COFs and the long-range order in the material not only benefit the light-harvesting capacity and transfer of photogenerated electrons to the surface but also prevent electron–hole pair combination. − The tunability of building blocks allows for linkage diversity in COFs, such as the β-ketoenamine linkage, , triazine linkage, − and olefin linkage, − which also contributes to the development of COF organic semiconductors with excellent optical and electronic properties. COFs have exhibited a high performance as heterogeneous organic photocatalysts, owing to their high porosity as well as good chemical and thermal stability. − Three key factors are required for COFs to qualify as photocatalysts: (i) a broad light absorption range, (ii) the separation and migration of photoexcited electron–hole pairs, and (iii) an appropriate oxidation–reduction potential. − Among them, the generation and migration rate of photogenerated electron–hole pairs determine the progress of the photocatalytic reaction. Therefore, it is essential to rationally design and synthesize COFs with a high capacity for photogenerated electron–hole separation and migration for application in photocatalysis.…”