Carbon Materials Derived from an Array of Zeolitic-Imidazolate Frameworks and Their Applications in Capacitive Deionization

Abstract

Capacitive deionization (CDI) represents one of the most thermodynamically efficient technologies for brackish water desalination, and its performance is highly dependent on the intrinsic properties of carbon materials. Ideally, CDI carbons should have high ion-accessible surface area, high porosity for ion mobility, great hydrophilic properties, excellent corrosion tolerance and good processability. Pyrolysis of precursory zeolitic-imidazolate frameworks (ZIFs) serves as a promising way to produce carbonaceous materials with great compositional and structural tunability.In this work, we systematically prepared an array of ZIFs (Zn(ligand)2) with different side-chain substitutions, which upon pyrolysis gave rise to carbon materials with variable elemental compositions, surface properties, wettability and graphitization levels; all are impacting the CDI performance. Zn(4abIm)2-C afforded the best salt adsorption capacity, while Zn(mIm)2-C showed the best overall salt adsorption capacity and rate; both exceeded the performance of the commercial carbon blacks.After careful correlation between the structures and the electrochemical results, it has been demonstrated that the CDI salt adsorption capacity increases with the carbon’s double layer capacitance. Additionally, graphitization level is significantly correlated with the CDI charge efficiency and energy consumption with more electronic conductive higher charge efficiency and lower energy consumption, which provides new insights to the field.