A series of quaternary ammonium salt-type gelators were designed, and two gelators with different self-assembly modes were obtained only by modulating the length of quaternary alkyl side chains. The self-assembly patterns of the xerogels were investigated by FTIR and XRD. This two xerogels had opposite surface zeta potentials and achieved selective adsorption of anionic and cationic dyes through electrostatic interaction. In binary anionic-cationic mixed dyes, xerogel with negatively charged surfaces preferentially captured cationic dyes, while xerogel with positively charged surfaces captured anionic dyes. Particularly, the xerogel with a negative surface charge showed excellent adsorption performance on crystal violet, with the equilibrium adsorption amount up to 1313.16 mg/g in 60 min. By loading the xerogel on the surface of melamine sponge skeleton, and the obtained modified sponge adsorbed the same kinds of dyes as the xerogel modified on it. And the adsorption capacities of the dyes were all significantly higher than those xerogels, especially the adsorption capacity for crystal violet reached 2488.22 mg/g.