A 2D porous porphyrin-based covalent organic framework for sulfur storage in lithium sulfur batteries

Covalent organic frameworks (COFs) represent an emerging class of porous crystalline materials and have recently shown interesting applications in energy storage. Herein, we report the construction of a cycle stable sulfur electrode by embedding sulfur into a 2D COF. The designed porphyrin-based COF (Por-COF), featuring a relatively large pore volume and narrow pore size distribution, has been employed as a host material for sulfur storage in Li-S batteries. With a 55% sulfur loading in the composite, the thus prepared cathode delivers a capacity of 633 mA h g(-1) after 200 cycles at 0.5C charge/discharge rates. Therefore, embedding sulfur in the nanopores of the Por-COF significantly improves the performance of the sulfur cathode. Considering the flexible design of COFs, we believe that it is possible to synthesize a 2D COF host with a suitable pore environment to produce more stable Li-S batteries, which may help in exploration of the structure -property relationship between the host material and cell performance.