title: Metal-Organic Frameworks for Resonant-Gravimetric Detection of Trace-Level Xylene Molecules.
abstract: As one of typical VOCs, xylene is seriously harmful to human health. Nowadays, however, there is really lack of portable sensing method to directly detect environmental xylene that has chemical inertness. Especially when the concentration of xylene is lower than the human olfactory threshold of 470 ppb, people are indeed hard to be aware of and avoid this harmful vapor. Herein the metal-organic framework (MOF) of HKUST-1 is first explored for sensing to the nonpolar molecule of p-xylene. And the sensing mechanism is identified that is via host-guest interaction of MOF with xylene molecule. By loading MOFs on mass-gravimetric resonant-cantilevers, sensing experiments for four MOFs of MOF-5, HKUST-1, ZIF-8, and MOF-177 approve that HKUST-1 has the highest sensitivity to p-xylene. The resonant-gravimetric sensing experiments with our HKUST-1 based sensors have demonstrated that trace-level p-xylene of 400 ppb can be detected that is lower than the human olfactory threshold of 470 ppb. We analyze that the specificity of HKUST-1 to xylene comes from Cu2+-induced moderate Lewis acidity and the "like dissolves like" interaction of the benzene ring. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is used to elucidate the adsorbing/sensing mechanism of HKUST-1 to p-xylene, where p-xylene adsorbing induced blue-shift phenomenon is observed that confirms the sensing mechanism. Our study also indicates that the sensor shows good selectivity to various kinds of common interfering gases. And the long-term repeatability and stability of the sensing material are also approved for the usage/storage period of two months. This research approves that the MOF materials exhibit potential usages for high performance chemical sensors applications.
authors.affiliation: School of Chemical and Environmental Engineering, Shanghai Institute of Technology , 100 Haiquan Road, Shanghai 201418, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.affiliation: State Key Lab of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences , 865 Changning Road, Shanghai 200050, China.
authors.forename: Pengcheng
authors.identifier: 0000-0001-8651-208X
authors.initials: P
authors.lastname: Xu
authors.affiliation: School of Chemical and Environmental Engineering, Shanghai Institute of Technology , 100 Haiquan Road, Shanghai 201418, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Zheng
authors.affiliation: State Key Lab of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences , 865 Changning Road, Shanghai 200050, China.
authors.forename: Haitao
authors.initials: H
authors.lastname: Yu
authors.affiliation: State Key Lab of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences , 865 Changning Road, Shanghai 200050, China.
authors.forename: Xinxin
authors.identifier: 0000-0001-6760-0957
authors.initials: X
authors.lastname: Li