Effect of Functional Groups of Metal–Organic Frameworks, Coated on Cotton, on Removal of Particulate Matters via Selective Interactions

Abstract

Currently, the contamination of air with particulate matters (PMs such as PM2.5 and PM10) is very severe, especially in Asian countries. Metal–organic frameworks (MOFs), with or without extra functional groups such as −NH2 and −NH-SO3H, were coated on conventional cotton to improve the efficiency of filters (composed of cotton fabric) in the removal of PMs from air. More importantly, the effect of the functional group of MOFs on the effective PM removal was analyzed quantitatively for the first time and could be interpreted via selective interactions. The removal efficiency was increased on the order: cotton < UiO-66/cotton < UiO-66-NH2/cotton < UiO-66-NH-SO3H/cotton, and the efficiency of the UiO-66-NH-SO3H-coated cotton was more than three times that of the pristine cotton. Moreover, the quality factor of cotton was more than doubled (or, 2.5–3 times) by UiO-66-NH-SO3H (only 20%) coating. The plausible mechanism for PM removal could be suggested based on the characterization of captured PM and introduced functional groups on MOFs. Based on the removal efficiency, pressure drop, and quality factor, coating of MOFs with functional groups, especially that are effective for charge separations (such as −SO3H), is one of the promising ways to improve the performance of PM filters. Moreover, the suggested strategy might be applied in capturing most of PMs composed of oxides, ammonium species, and carbons with polar outside.

Removal of Particulate Matters by Using Zeolitic Imidazolate Framework-8s (ZIF-8s) Coated onto Cotton: Effect of the Pore Size of ZIF-8s on Removal

“…This means that there might be small interaction sites on large PMs that can be intruded onto the pore of MOFs for interaction. To understand the characteristics of PMs, FT-IR was applied to check the properties of the captured PM, after filtration for 12 h. As presented in Figure , the PMs have a few polar bonds like CO, CO, and NH, which is agreeable with earlier reports. , Moreover, PMs, derived from burned incense, are composed of carbonaceous materials with polar outside (and nonpolar inside), as has been reported earlier. ,,, Therefore, the structure of the captured PM in this study can be described as carbons with polar outside (because of CO, CO, and NH bonds) (Scheme a).…”

“…In brief, DEA-ZIF-8/EC showed the best performances in the removal of PMs in view of RE and QF. Additionally, EC had quite a high RE and PD, compared with an ordinary cotton, 30,31 because the thickness of EC is larger than that of a simple cotton that was used so far. 30,31 The QF of EC is similar to that of the conventional cotton, 30,31 since QF relies on both the RE and the PD.…”

“…Additionally, EC had quite a high RE and PD, compared with an ordinary cotton, 30,31 because the thickness of EC is larger than that of a simple cotton that was used so far. 30,31 The QF of EC is similar to that of the conventional cotton, 30,31 since QF relies on both the RE and the PD. 1,2 The removal of PMs was carried out with the best DEA-ZIF-8/EC and the worst EC filters at various initial (before filtration) concentrations of PMs.…”

“…Although there are several results on PM removal with MOFs to increase the performances or to perfectly remove PMs from air, there is little result on understanding the basics of PM removal with MOFs . A few important parameters like charge separation (with polar functional groups), , high porosity, voidage, special structure, − and open metal site/defect − of MOFs have been suggested as the reason to increase their performances in PM removal. Although MOFs have an advantage of huge porosity and possible loading of functionality for effective PM removal, detailed research is necessary to know the basics of PM removal with MOFs for further development or industrialization.…”

“…Although there are several results on PM removal with MOFs to increase the performances or to perfectly remove PMs from air, there is little result on understanding the basics of PM removal with MOFs. 29 A few important parameters like charge separation (with polar functional groups), 30,31 high porosity, 32 voidage, 33 special structure, 34−37 In this work, we studied PM removal by using zeolitic imidazolate framework-8s (ZIF-8s) with pore sizes in different dimensions. ZIF-8, 41,42 with a sodalite (SOD) structure, is one of the widely studied ZIFs, a subclass of MOFs.…”