So far, analogous MOFs [34] with different central metals have been reported to influence gas-phase (CO2, methane, ammonia, etc.) and non-aqueous–liquid-phase adsorptions [34]. However, Tong et al. reported the influence of framework metal ions in dyes adsorption over MIL-100-Fe/Cr. MIL-100-Fe and MIL-100-Cr have similar surface areas (1770 and 1760 m2/g) and pore volumes (0.76 and 0.75 cm3/g); however they behave very differently during adsorption of MO and MB from water [126]. In the adsorption of MO, MIL-100-Fe showed very high adsorption (1045.2 mg/g) compared with MIL-100-Cr (211.8 mg/g). Because of the higher binding energy (in absolute value) of water molecules with metal sites of MIL-100-Cr (the binding energies of water with MIL-100-Cr and MIL-100-Fe are −94.7 and −75.5 kJ/mol, respectively), the competitive adsorption of MO and water is more prominent at the surface of MIL-100-Cr, and adsorption of water molecules generally takes place at the apertures of pentagonal and hexagonal windows; this tends to limit the accessibility of the cages of MIL-100-Cr for the MO to a large extent. However, in the case of MB, both the MOFs showed very good adsorption (736.2 and 645.3 mg/g for MIL-100-Fe and MIL-100-Cr, respectively), because, in this case, electrostatic interactions between the cationic dye and negatively charged MOF surface become dominant. Moreover, the huge difference between the adsorption behaviors of anionic and cationic dyes (MO and MB) with MIL-100-Fe/Cr becomes important for selective separation of dyes (see Fig. 7). From a 50:50 mixture of MO and MB, MIL-100-Cr selectively adsorbs MB over MO, showing its advantage in MO–MB mixture separation. The effects of the central metal ions on the ADS of model fuels have been reported [75] and [83], although in non-aqueous phase adsorptions.