title: Probing the adsorption characteristic of metal-organic framework MIL-101 for volatile organic compounds by quartz crystal microbalance.
abstract: As volatile organic compounds (VOCs) are a major group of air pollutants, development of materials for efficient adsorption and removal of VOCs is of great significance in both environmental and analytical sciences. Here we report metal-organic frameworks (MOFs) MIL-101 for the effective adsorption of VOCs at atmospheric pressure. A simple device was designed for quartz crystal microbalance (QCM), and six VOCs with various functional groups and polarities, i.e., n-hexane, toluene, methanol, butanone, dichloromethane, and n-butylamine, were chosen as targets to probe the adsorption properties of MIL-101. The developed device allows measurement of the adsorption isotherms and monitoring of the dynamic process for the adsorption of VOCs on MOFs, and also provides a useful tool for characterization of MOFs. The adsorption isotherms of the VOCs on MIL-101 followed the Dubinin-Astakhov equation with the characteristic energy from 5.70 (methanol) to 9.13 kJ mol(-1) (n-butylamine), Astakhov exponent from 0.50 (n-butylamine) to 3.03 (n-hexane), and the limiting adsorption capacity from 0.08 (n-hexane) to 12.8 (n-butylamine) mmol g(-1). MIL-101 exhibited the strongest affinity to n-butylamine, but the weakest affinity to n-hexane. The determined Astakhov exponents and the isosteric heats of adsorption revealed the energetic heterogeneity of MIL-101. MIL-101 showed the most energetically homogeneous for n-hexane, but the most energetically heterogeneous for n-butylamine. The dynamic process of adsorption monitored by the QCM system demonstrated the distribution of the sorption sites within MIL-101. The metal sites within the MIL-101 were vital in adsorption process. MIL-101 gave much higher affinity and bigger adsorption capacity to VOCs than activated carbon, offering great potential for real applications in the adsorption and removal of VOCs.
authors.affiliation: Research Center for Analytical Sciences, and Key Laboratory of Functional Polymer Materials, Ministry of Education, College of Chemistry, Nankai University, Tianjin 300071, China.
authors.forename: Chan-Yuan
authors.initials: CY
authors.lastname: Huang
authors.forename: Ming
authors.initials: M
authors.lastname: Song
authors.forename: Zhi-Yuan
authors.initials: ZY
authors.lastname: Gu
authors.forename: He-Fang
authors.initials: HF
authors.lastname: Wang
authors.forename: Xiu-Ping
authors.initials: XP
authors.lastname: Yan
mesh_terms: D000327:Adsorption; D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry*; D001274:Atmospheric Pressure; D002606:Charcoal / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry*; D003460:Crystallization; D006858:Hydrofluoric Acid / Q000737:chemistry; D058525:Quartz Crystal Microbalance Techniques; D055549:Volatile Organic Compounds / Q000032:analysis / Q000737:chemistry*
chemical_list: D000393:Air Pollutants; D056831:Coordination Complexes; D055549:Volatile Organic Compounds; D002606:Charcoal; D006858:Hydrofluoric Acid