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Chem Sci

Title:		A photoprogrammable electronic nose with switchable selectivity for VOCs using MOF films
Author(s):		Qin P; Okur S; Li C; Chandresh A; Mutruc D; Hecht S; Heinke L;
Address:		"Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG) Hermann-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen Germany Lars.Heinke@kit.edu. Humboldt-Universitat zu Berlin, Department of Chemistry & IRIS Adlershof Brook-Taylor-Strasse 2 12489 Berlin Germany. DWI - Leibniz Institute for Interactive Materials Forckenbeckstr. 50 52074 Aachen Germany. RWTH Aachen University, Institute of Technical and Macromolecular Chemistry Worringer Weg 2 52074 Aachen Germany"
Journal Title:		Chem Sci
Year:		2021
Volume:		20211122
Issue:		47
Page Number:		15700 - 15709
DOI:		10.1039/d1sc05249g
ISSN/ISBN:		2041-6520 (Print) 2041-6539 (Electronic) 2041-6520 (Linking)
Abstract:		"Advanced analytical applications require smart materials and sensor systems that are able to adapt or be configured to specific tasks. Based on reversible photochemistry in nanoporous materials, we present a sensor array with a selectivity that is reversibly controlled by light irradiation. The active material of the sensor array, or electronic nose (e-nose), is based on metal-organic frameworks (MOFs) with photoresponsive fluorinated azobenzene groups that can be optically switched between their trans and cis state. By irradiation with light of different wavelengths, the trans-cis ratio can be modulated. Here we use four trans-cis values as defined states and employ a four-channel quartz-crystal microbalance for gravimetrically monitoring the molecular uptake by the MOF films. We apply the photoprogrammable e-nose to the sensing of different volatile organic compounds (VOCs) and analyze the sensor array data with simple machine-learning algorithms. When the sensor array is in a state with all sensors either in the same trans- or cis-rich state, cross-sensitivity between the analytes occurs and the classification accuracy is not ideal. Remarkably, the VOC molecules between which the sensor array shows cross-sensitivity vary by switching the entire sensor array from trans to cis. By selectively programming the e-nose with light of different colors, each sensor exhibits a different isomer ratio and thus a different VOC affinity, based on the polarity difference between the trans- and cis-azobenzenes. In such photoprogrammed state, the cross-sensitivity is reduced and the selectivity is enhanced, so that the e-nose can perfectly identify the tested VOCs. This work demonstrates for the first time the potential of photoswitchable and thus optically configurable materials as active sensing material in an e-nose for intelligent molecular sensing. The concept is not limited to QCM-based azobenzene-MOF sensors and can also be applied to diverse sensing materials and photoswitches"
Keywords:
Notes:		"PubMed-not-MEDLINEQin, Peng Okur, Salih Li, Chun Chandresh, Abhinav Mutruc, Dragos Hecht, Stefan Heinke, Lars eng England 2022/01/11 Chem Sci. 2021 Nov 22; 12(47):15700-15709. doi: 10.1039/d1sc05249g. eCollection 2021 Dec 8"