Conjugated Phthalocyanine-Based Mesoporous Covalent Organic Frameworks for Efficient Anodic Lithium Storage

Abstract

Organic anode materials have been recognized as promising candidates for low-cost and sustainable lithium-ion batteries (LIBs), which however suffer from the inferior cycling stability and low conductivity with unsatisfactory LIBs performance. Herein, two conjugated phthalocyanine-based covalent organic frameworks (COFs), namely CoPc-Ph-COF and CoPc-3Ph-COF, are synthesized by the nucleophilic substitution reaction of hexafluorophthalocyanine cobalt (II) (CoPcF₁₆) with 1,2,4,5-tetrahydroxybenzene and 9,10-dimethyl-2,3,6,7-tetrahydroxyanthracene, respectively. Powder X-ray diffraction and electron microscopy analysis reveal the crystalline porous structure of both COFs with a pore size of 1.6-2.4 nm, enabling facile ion transportation. Immersion experiments demonstrate the excellent stability of both COFs. I–V curve measurement discloses the superb conductivity of both COFs due to their fully π-conjugated frameworks. These merits, in combination with their N-rich skeleton, endow the two COFs with excellent anodic Li⁺ storage performance in terms of high specific capacities, superb rate performance, and good cycling stability. In particular, CoPc-3Ph-COF suggests a large reversible capacity of 1086 mA h g⁻¹ at 100 mA g⁻¹, superior to most reported organic LIBs anodes, exhibiting its promising application in high-performance LIBs.