A metal-OH group modification strategy to prepare highly-hydrophobic MIL-53-Al for efficient acetone capture under humid conditions

A series of highly-hydrophobic MIL-53-Al(MIL = Materials of Institut Lavoisier) frameworks synthesized via decoration of the Al-OH groups by alkyl phosphonic acid were developed as adsorbents for removing acetone from humid gas streams.The newly prepared materials were characterized by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), scanning electron microscope(SEM), N_(2) adsorption-desorption and thermogravimetric analysis(TGA).Their adsorption behaviors toward acetone vapor under dry and wet conditions were studied subsequently.Results showed that alkyl phosphonic acid was successfully grafted into MIL-53-Al skeleton through coordinating interaction with Al3+generating MIL-53-Al@C_(x)(x = 12, 14, 18).The MIL-53-Al@C_(x) exhibited similar crystal structure and thermal stability to parent MIL-53-Al.Furthermore, the modified materials showed significantly enhanced hydrophobicity.The water vapor uptake of MIL-53-Al@C_(14) decreased by 72.55%at 75% relative humidity(RH).Dynamic adsorption experiments demonstrated that water vapor had almost no effect on the acetone adsorption performance of MIL-53-Al@C_(14).Under the condition of 90% RH, the acetone adsorption capacity of MIL-53-Al@C_(14) was 102.98% higher than that of MIL-53-Al.Notably, MIL-53-Al@C_(14) presented excellent adsorption reversibility and regeneration performance in 10 adsorption-desorption cycles.Taken together, the strategy of metal-OH group modification is an attractive way to improve the acetone adsorption performance over metal-organic frameworks(MOFs) under humid conditions.Besides, MIL-53-Al@C_(14) would be deemed as a promising candidate for capturing acetone in high moisture environment.