Currently, air contamination, especially with particulate matters (PMs), is severe in several countries. To increase the efficiency of air filters in PM removal, metal−organic frameworks (MOFs, here, Zr-MOFs, especially with functional groups (FGs) such as −NO 2 ) were coated, after synthesis, onto cotton using covalent bonding for the first time. The removal efficiencies (REs) and quality factors (QFs) of cottons with or without MOFs were in the order: cotton < Zr-MOF/cotton < Zr-MOF-NH 2 /cotton < Zr-MOF-NH-SO 3 H/cotton < Zr-MOF-NH 3 + Cl − /cotton < Zr-MOF-NO 2 /cotton. This monotonic increase in the PM removal efficiency or QF could be explained with the order of charge separation or developed charges (total, in absolute value: ∼0 to 2.0) on FGs of MOFs. Importantly, Zr-MOF-NO 2 coating on cotton showed a very high increase in the performance of cotton in PM removal. QF and RE of Zr-MOF-NO 2 /cotton were 4.6 times and 6.2 times of the bare cotton, respectively, for PM2.5 removal, even with a very small increase in pressure drop (3 Pa or less) with MOF coating. Based on the research, it can be suggested that coating MOFs on substrates is a promising way to improve the performances of air filters for PM removal, especially when MOFs have FGs that can have large charge separation such as −NO 2 . This work may pave a way to utilize a functionalized MOF in the effective removal of PMs from air.
Effective removal
of particulate matters (PMs) from air is very
important for our safe environment, health, and sustainability. In
this study, isostructural (with the same topology of fcu) Zr-metal–organic frameworks (Zr-MOFs) such as UiO-66, UiO-67,
and DUT-52 (with different porosity) were coated onto cotton and utilized
in PM removal from air to understand the contribution of MOFs in improving
the performances of air filters. Moreover, UiO-66s with different
porosities were also prepared under different conditions from the
same reaction mixture. Experiments to remove PMs such as PM2.5 and
PM10 showed a critical role of porosity of coated MOFs in the PM removal.
Or, the removal efficiency or quality factor increased linearly with
the increasing surface area of all the studied MOFs, irrespective
of the applied linkers (for synthesizing different MOFs) and synthesis
conditions (for different porosities of UiO-66s). Therefore, this
work confirms, for the first time, that the porosity of MOF is one
of the most important parameters to improve the performance of air
filter (to remove PMs) that is modified with coated MOFs. Moreover,
we could suggest why porous materials with small pores were effective
in capturing PMs (larger in size than pores of porous materials) from
air.
Removal of particulate matter (PM)
like PM2.5 and PM10 from air
was carried out with cotton coated with metal–organic frameworks
(MOFs) having various pore sizes to understand the effect of the pore
size of MOFs (here, ZIF-8s) on the performances in PM elimination.
Both removal efficiency and quality factor, based on the unit surface
area of ZIF-8s, in the filtration of PMs with ZIF-8/cotton did not
rely considerably on the pore size of ZIF-8s. More importantly, small
pores (even less than 0.5 nm) of conventional MOFs like ZIF-8 are
more than enough in the elimination of large PMs like PM10 with a
size of microns probably because small active sites (such as polar
functional groups) on PMs can interact with porous materials having
polarity. Additionally, electrostatic interactions between PMs and
porous materials could be confirmed as a plausible mechanism for PM
removal with ZIF-8/cotton.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.