Abstract

Recently, effective removal of toxic gases from humid streams has been an urgent global issue, especially at low concentrations due to increase in air pollutant emission standards. In this work, a series of selectively modified MIL-101 s was prepared by blocking coordinatively unsaturated sites (CUSs) with hydrophobic amine compounds containing –F or long alkyl groups. The nucleophilic quinuclidine (QN) was consecutively encapsulated into the pores of hydrophobic MIL-101 s to remove CH3I by alkylation. The direct correlation between the hydrophobic index (HI) of adsorbents and the CH3I removal performance in a humid environment was systematically investigated for the first time by progressively blocking the CUSs with different amounts of hydrophobic amines including 4-(trifluoromethyl) benzylamine (TFM-BA). Among them, QN@MIL-101-TFM-BA exhibited the unprecedented removal efficiency exceeding 99.999% at 303 K and RH 95% for 11 days, outperforming over 280 times compared to the conventional adsorbents. The strong affinity between QN and CH3I is thoroughly investigated by X-ray photoelectron spectroscopy (XPS) and elemental mapping. MIL-101-TFM-BA showed outstanding removal performance even for HCHO, proving the versatile use of the prepared hydrophobic metal–organic frameworks adsorbents in realistic condition.

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