Curating Metal–Organic Frameworks To Compose Robust Gas Sensor Arrays in Dilute Conditions

Abstract

Metal–organic frameworks (MOFs), tunable, nanoporous materials, are alluring recognition elements for gas sensing. Mimicking human olfaction, an array of cross-sensitive, MOF-based sensors could enable analyte detection in complex, variable gas mixtures containing confounding gas species. Herein, we address the question: given a set of MOF candidates and their adsorption properties, how do we select the optimal subset to compose a sensor array that accurately and robustly predicts the gas composition via monitoring the adsorbed mass in each MOF? We first mathematically formulate the MOF-based sensor array problem under dilute conditions. Instructively, the sensor array can be viewed as a linear map from gas composition space to sensor array response space defined by the matrix H of Henry coefficients of the gases in the MOFs. Characterizing this mapping, the singular value decomposition of H is a useful tool for evaluating MOF subsets for sensor arrays, as it determines the sensitivity of the predicted gas composition to measurement error, quantifies the magnitude of the response to changes in composition, and recovers which direction in gas composition space elicits the largest/smallest response. To illustrate, on the basis of experimental adsorption data, we curate MOFs for a sensor array with the objective of determining the concentration of CO2 and SO2 in the gas phase.

Metal–organic framework thin films as versatile chemical sensing materials

“…The straightforward transduction pathway for QCM, whereby the gas uptake for the partial pressure of a particular gas is directly related to the change in acoustic frequency via the Sauerbrey equation, has allowed for various mathematical investigations into theoretical MOF QCM arrays. 173,174 In one of these mathematical studies, a priori data of the gas adsorption properties for individual MOFs, as determined by molecular modelling and simulation, are used to curate the ideal MOF selection for sensor arrays. 173 One experimental example of a QCM array composed of three different surface-mounted MOF (SURMOF) thin films (CuBTC, Cu-benzene dicarboxylate, and Cubiphenyl dicarboxylate) was applied toward the discrimination of different volatile plant oil odors.…”

“…173,174 In one of these mathematical studies, a priori data of the gas adsorption properties for individual MOFs, as determined by molecular modelling and simulation, are used to curate the ideal MOF selection for sensor arrays. 173 One experimental example of a QCM array composed of three different surface-mounted MOF (SURMOF) thin films (CuBTC, Cu-benzene dicarboxylate, and Cubiphenyl dicarboxylate) was applied toward the discrimination of different volatile plant oil odors. 175 This 3 SURMOF QCM array, in combination with k-nearest neighbour analysis algorithms, was able to discriminate between six VPOs and their binary mixtures with nearly 100% accuracy.…”

Material Screening for Gas Sensing using an Electronic Nose: Gas Sorption Thermodynamic and Kinetic Considerations

“…To this aim, Wilmer and coworkers and Simon and coworkers have recently provided excellent screening frameworks. [37][38][39][40][41][42] The former comprises of computational studies aimed at providing a probabilistic metric to quantify sensing performance of an array and at efficiently screening several materials using an evolutionary optimization algorithm for CH 4 and CO 2 sensing. The latter comprises of computational studies aimed at using elegant mathematical concepts to screen materials under dilute conditions for a two-and three-gas system and to evaluate the fitness of combinations of materials in a sensor array for a two-gas system.…”

Genetic Algorithm Design of MOF-based Gas Sensor Arrays for CO2-in-Air Sensing

“…And at levels of 30% and greater, exposure can lead to a loss of consciousness in only a matter of seconds [8,20]. Clearly, rapid, sensitive, and portable (even wearable) CO 2 sensors would benefit many people.Recently, a number of studies have investigated the use of metal-organic frameworks (MOFs) for improving electronic noses [23][24][25][26][27]. MOFs are promising materials for gas adsorption applications due to their nanoporous nature, high internal surface areas, and ease of tunability [28][29][30][31][32][33][34].…”

“…Similarly, there has been little work on systematically finding the best combinations of MOFs for an array, and with thousands of MOFs to choose from, and thus well over 10 50 possible arrays, determining the top performing arrays is highly non-trivial. A recent paper by Sturluson et al made significant progress in this area by computationally designing MOF-based gas sensing arrays for the detection of CO 2 and SO 2 in dilute conditions [27]. In their paper, they calculated the Henry's coefficients, which are used to predict adsorption of gases in dilute concentrations, for each gas/MOF to design arrays with maximal complementarity, and consequently the best signal.In this paper, we use a computational methodology to find optimal MOF-based gas-sensing arrays for CO 2 detection in ambient air, where the MOFs are assumed to be deposited as thin films on sensors that detect changes in mass, such as surface acoustic wave (SAW) devices, as shown in Figure 1, or quartz crystal microbalances (QCMs).…”