Mass transfer of toluene in a series of metal–organic frameworks: molecular clusters inside the nanopores cause slow and step-like release

Chun, Li; Zhang, Zejun; Heinke, Lars

doi:10.1039/d1cp05560g

Cited by 8 publications

(10 citation statements)

References 60 publications

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“…67,68 The orientation of the molecules inside the lozenge-shaped pores avoids clustering phenomena, reported to increase desorption times for aromatic molecules. 69 This supports the high mobility of toluene in the porosity of DUT-4, in line with the fast response of the DUT-4@QCM sensor. Finally, the stability of the MOF@QCM was investigated.…”

Section: Dut-4 As a Toluenesupporting

confidence: 76%

“…The simulated values of the D self for toluene are ranging from 3.40 × 10 –9 (300 K) to 1.03 × 10 –8 m 2 /s (450 K) corresponding to a relatively fast transport as compared to the scenario encountered for the same guest in some typical zeolites like ZSM-5 . The activation energy of 8.5 kJ/mol determined from the Arrhenius plot (i.e., in D self = f (1000/ T ) as depicted in Figure S15) is relatively small than that reported for other porous sorbents, e.g., E a = 20 kJ/mol for Na–X zeolite. , The orientation of the molecules inside the lozenge-shaped pores avoids clustering phenomena, reported to increase desorption times for aromatic molecules . This supports the high mobility of toluene in the porosity of DUT-4, in line with the fast response of the DUT-4@QCM sensor.…”

Section: Resultsmentioning

confidence: 78%

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Airborne Toluene Detection Using Metal–Organic Frameworks

Gulcay-Ozcan

Iacomi

Rioland

et al. 2022

ACS Appl. Mater. Interfaces

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The pollution of indoor air is a major worldwide concern in our modern society for people's comfort, health, and safety. In particular, toluene, present in many substances including paints, thinners, candles, leathers, cosmetics, inks, and glues, affects the human health even at very low concentrations throughout its action on the central nervous system. Its prevalence in many workplace environments can fluctuate considerably, which led to firm regulation with exposure limits varying between 50 and 400 ppm depending on exposure time. This therefore requires the development of technologies for an accurate detection of this contaminant. Metal−organic frameworks have been proposed as promising candidates to detect and monitor a series of molecules at even extremely low concentrations owing to the high tunability of their functionality. Herein, a high-throughput Monte Carlo screening approach was devised to identify the best MOFs from the computation-ready, experimental (CoRE) metal−organic framework (MOF) density-derived electrostatic and chemical (DDEC) database for the selective capture of toluene from air at room temperature, with the consideration of a ternary mixture composed of extremely low-level concentration of toluene (10 ppm) in oxygen and nitrogen to mimic the composition of air. An aluminum MOF, DUT-4, with channel-like micropores was identified as an excellent candidate for the selective adsorption of toluene from air with a predicted adsorption uptake of 0.5 g/g at 10 ppm concentration and room temperature. The toluene adsorption behavior of DUT-4 at low equivalent concentrations, alongside its sensing performance, was further experimentally investigated by its incorporation in a quartz crystal microbalance sensor, confirming the promises of DUT-4. Decisively, the resulting high sensitivity and fast kinetics of our developed sensor highlight the applicability of this hand-in-hand computational−experimental methodology to porous material screening for sensing applications.

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Section: Dut-4 As a Toluenesupporting

confidence: 76%

Section: Resultsmentioning

confidence: 78%

Airborne Toluene Detection Using Metal–Organic Frameworks

Gulcay-Ozcan

Iacomi

Rioland

et al. 2022

ACS Appl. Mater. Interfaces

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“…By vapor uptake experiments using toluene and methanol as probe molecules, the photoresponsive properties of the Fulg@UiO-68 material were explored, especially with respect to the guest mass transfer and host–guest interaction. The amount of the guest uptake was quantified with a quartz crystal microbalance (QCM) . The uptake experiments were performed for the sample upon UV light irradiation, resulting in the C -form (i.e., 60% C and 40% E ), and upon green light irradiation, resulting in the E -form (100% E ).…”

Section: Resultsmentioning

confidence: 99%

“…The amount of the guest uptake was quantified with a quartz crystal microbalance (QCM). 37 The uptake experiments were performed for the sample upon UV light irradiation, resulting in the C-form (i.e., 60% C and 40% E), and upon green light irradiation, resulting in the E-form (100% E). Each uptake experiment was performed six times (see Figure S3), and representative toluene uptake curves are shown in Figure 5a.…”

Section: Resultsmentioning

confidence: 99%

Nanoporous Metal–Organic Framework Thin Films with Embedded Fulgide for Light-Modulated Guest Adsorption and Diffusion

Zhang

Heinke

2022

Langmuir

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Smart and photoresponsive materials and thin films allow the dynamic remote control of their central properties. By incorporation of photochromic molecules in nanoporous metal–organic frameworks (MOFs), the interaction between the MOF host and the guest molecules in the pores can be modified. Here, a MOF film of type UiO-68 is presented in which the photoswitchable feature is added by embedment of photochromic fulgide molecules of type Aberchrome 670 in the pores. The photoisomerization in the pores is explored by UV–vis and infrared spectroscopy, and the transient uptake of toluene and methanol probe molecules is explored using a quartz crystal microbalance. For the first time, a fulgide-based nanoporous material is used to remote-control the adsorption and diffusion properties. We find that the toluene uptake amount can be increased by 37% and the toluene diffusion coefficient can be increased by 40% when reversibly photoswitching the embedded fulgide from its E-form to C-form. In this way, this study aims to contribute to the field of light-responsive nanoporous materials and thus expands the range of smart coatings.

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“…(Previous dew-point experiments with the gas flow setup showed that the resulting vapor pressure is only slightly smaller than the saturated vapor pressure. 46,54 ) The other stream is pure nitrogen. Then, both streams are merged and the VOC concentration can be controlled by adjusting the flow rates.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

VOC Mixture Sensing with a MOF Film Sensor Array: Detection and Discrimination of Xylene Isomers and Their Ternary Blends

et al. 2022

Self Cite

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Detection and recognition of volatile organic compounds (VOCs) are crucial in many applications. While pure VOCs can be detected by various sensors, the discrimination of VOCs in mixtures, especially of similar molecules, is hindered by crosssensitivities. Isomer identification in mixtures is even harder. Metal−organic frameworks (MOFs) with their well-defined, nanoporous, and versatile structures have the potential to improve the VOC sensing performance by tailoring the adsorption affinities. Here, we detect and identify ternary xylene isomer mixtures by using an array of six gravimetric, quartz crystal microbalance (QCM)-based sensors coated with selected MOF films with different isomer affinities. We use classical molecular simulations to provide insights into the sensing mechanism. In addition to the attractive interaction between the analytes and the MOF film, the isomer discrimination is caused by the rigid crystalline framework sterically controlling the access of the isomers to different adsorption sites in the MOFs. The sensor array has a very low limit of detection of 1 ppm for each pure isomer and allows the isomer discrimination in mixtures. At 100 ppm, 16 different ternary o−p−m-xylene mixtures were identified with high classification accuracy (96.5%). This work shows the unprecedented performance of MOF-sensor arrays, also referred to as MOF-electronic nose (MOF-enose), for sensing VOC mixtures. Based on the study, guidelines for detecting and discriminating complex mixtures of volatile molecules are also provided.

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Mass transfer of toluene in a series of metal–organic frameworks: molecular clusters inside the nanopores cause slow and step-like release

Abstract: Toluene forms dimers in sufficiently large pores of MOFs of UiO-type. During the release process, the dimer break-up rather than the diffusion is rate limiting, causing a step-like desorption kinetics with a local maximum of the release rate.

Cited by 8 publications

References 60 publications

Airborne Toluene Detection Using Metal–Organic Frameworks

Airborne Toluene Detection Using Metal–Organic Frameworks

Nanoporous Metal–Organic Framework Thin Films with Embedded Fulgide for Light-Modulated Guest Adsorption and Diffusion

VOC Mixture Sensing with a MOF Film Sensor Array: Detection and Discrimination of Xylene Isomers and Their Ternary Blends

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