Boosted capture of volatile organic compounds in adsorption capacity and selectivity by rationally exploiting defect-engineering of UiO-66(Zr)

Abstract The great challenge in capturing harmful volatile organic compounds (VOCs) using Metal-Organic-Frameworks (MOFs) materials still rely on rationally modifying its appreciable microporous character in hydrostable structure. Defected structure in MOFs might be very beneficial for creating expected engineering adsorbent. In this study, defect-engineering UiO-66 via imparting acetic acid (HAc) as an interfering agent was successfully fabricated by a simple hydrothermal method. The physicochemical properties of the obtained materials were intensively ascertained and identified through a series of applicable characterizations. By the proper participation of tuning concentration of HAc (HAc/TAc=24, molar ratio), the obtained adsorbent UiO-66-1.0HAc was endowed with the highest adsorption capacity for benzene (367.13 mg g-1, 25 °C) in the known UiO-66 materials, which was 41.9% higher than that of the non-defected UiO-66. With a higher optimized added amount of HAc (HAc/TAc=48, molar ratio), the adsorption capacity of UiO-66-2.0HAc to toluene achieved the highest capture values (410.21 mg g-1, 25 °C), which boosted 93% compared with the original counterpart. This demonstrated improvement was ascribable to the imparted structural defect-engineering derived from the missing-linkers of MOFs increasing the unsaturated adsorption site and concomitant enlarged structural properties of the resultant material. By identifying the DIH (Difference in adsorption heat), the obtained maximum adsorption selectivity of UiO-66-1.0HAc to toluene/water was further enhanced to 64.4, which was 3.7 times the original UiO-66, owing to the existed defect-engineering in adsorbents, indicating the potential differential competitive adsorption effect for benzene and toluene under humid conditions.