Fig. 4. Metal-based and ionic CHs. (A) Ag-based CHs. Reproduced from ref. 96 with the permission of Elsevier, copyright 2019. (B) PAA-based ionic CHs. Reproduced from ref. 110 with the permission of Elsevier, copyright 2021. (C) Zwitterion-based CHs. Reproduced from ref. 114 with the permission of Wiley-VCH, copyright 2021.