Synergistic effects between –NO2 groups and open metal sites lead to optimal binding of CO2 molecules within MFM-102-NO2via hydrogen bonding to C–H groups.
The development of efficient sorbent materials for sulfur
dioxide
(SO
2
) is of key industrial interest. However, due to the
corrosive nature of SO
2
, conventional porous materials
often exhibit poor reversibility and limited uptake toward SO
2
sorption. Here, we report high adsorption of SO
2
in a series of Cu(II)-carboxylate-based metal–organic framework
materials. We describe the impact of ligand functionalization and
open metal sites on the uptake and reversibility of SO
2
adsorption. Specifically, MFM-101 and MFM-190(F) show fully reversible
SO
2
adsorption with remarkable capacities of 18.7 and 18.3
mmol g
–1
, respectively, at 298 K and 1 bar; the
former represents the highest reversible uptake of SO
2
under
ambient conditions among all porous solids reported to date.
In situ
neutron powder diffraction and synchrotron infrared
microspectroscopy enable the direct visualization of binding domains
of adsorbed SO
2
molecules as well as host–guest
binding dynamics. We have found that the combination of open Cu(II)
sites and ligand functionalization, together with the size and geometry
of metal–ligand cages, plays an integral role in the enhancement
of SO
2
binding.
We
report the first example of crystallographic observation of
acetylene binding to −NO2 groups in a metal–organic
framework (MOF). Functionalization of MFM-102 with −NO2 groups on phenyl groups leads to a 15% reduction in BET surface
area in MFM-102-NO2. However, this is coupled to a 28%
increase in acetylene adsorption to 192 cm3 g–1 at 298 K and 1 bar, comparable to other leading porous materials.
Neutron diffraction and inelastic scattering experiments reveal the
role of −NO2 groups, in cooperation with open metal
sites, in the binding of acetylene in MFM-102-NO2.
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