High-Efficient removal of mercury in water by the flexible NH2-MIL-53(Al): Exploiting the gate opening effect

Flexible metal-organic frameworks (MOFs) with the gate opening feature can optimize the removal efficiency on the adsorption behavior by accommodating to the specific target molecules. In this study, a flexible MOF denoted as NH2-MIL-53(Al) was investigated to remove Hg(II) from water, in which the adsorption capacities of largepore NH2-MIL-53(Al) (NH2-MIL-53(Al)-LP) for Hg(II) reached 433.20 mg/g, which is about 4 times higher than narrow -pore NH2-MIL-53(Al) (112.75 mg/g). Further, the kinetic experiment also revealed that nearly 90 % Hg(II) can be captured within 60 min for NH2-MIL-53(Al)-LP. Advanced characterizations and density functional theory calculations demonstrated that the strong coordination of the amino and oxygen centers on NH2-MIL-53 (Al) -LP to Hg(II). Importantly, molecular dynamic simulation verified the gate opening effect of NH2-MIL-53(Al)- LP, as the faster diffusivity of Hg(II) ions in NH2-MIL-53(Al)-LP was observed. This work provides another opportunity in designing the pore geometry of porous materials for water remediation.