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Sun et al. Microstructures 2023;3:2023032 https://dx.doi.org/10.20517/microstructures.2023.32 Page 9 of 21

Figure 5. Structure of MOF-808-AA and structural schemes of the coordinatively loaded amino acids. Reproduced with permission
from Lyu et al. [101] . Copyright 2022 American Chemical Society.

dichotomy isotherms, and dynamic breakthrough measurements. This study enhances our comprehension
of CO capture in MOFs by uncovering the mechanism in which amine groups, firmly attached to the MOF
2
structure, generate molecules within the pores that facilitate the adsorption and desorption of CO at
2
[101]
relatively low temperatures without requiring any heating .
Among physisorption materials, anion-functionalized MOFs are novel porous materials composed of metal
moieties, organic linkers, and inorganic anions [102,103] . In recent years, anionic-functionalized MOFs have
gradually made their presence felt in the field of CO capture. The reticular design approach can effectively
2
regulate the pore chemistry of anionic-functionalized MOFs by utilizing molecular building units. As
previously reported by Bhatt et al., NbOFFIVE-1-Ni and SIFSIX-3-Cu exhibit CO adsorption capacities of
2
1.3 and 1.2 mmol g at a low concentration of 400 ppm and 298 K, respectively . Their study also shows
[104]
-1
that reducing the pore size of the porous adsorbent facilitates enhanced interaction between the CO
2
molecules and the main framework, resulting in high CO uptake at lower pressures.
2
ZU-16-Co is an anion-functionalized MOF with fine-tuned pore chemistry featuring one-dimensional (1D)
pores modified by enriched F atoms that can effectively trap CO at concentrations of 400-10,000 ppm.
2
Highly organized Lewis basic sites of anions limited to the ultramicroporous pores substantially enhance the
ability to bind CO [Figure 6]. This work clarifies the structure-function relationship of ZU-16-Co in
2
capturing CO and demonstrates its suitability for decarbonization at low concentrations .
[105]
2
Two polar sulfonated oxygen-rich 3D MOFs, {[Zn (TPOM)(3,7-DBTDC) ] 7H O·DMA} (1) and
2
2
2
n
{[Cd (TPOM)(3,7-DBTDC) ]·6H O·3DMF} (2) (TPOM = tetrakis(4-pyridyloxymethylene)-methane), were
n
2
2
2
synthesized by a solvothermal approach by Chakraborty et al. . Structural diversity was achieved by
[106]
changing the metal centers. Due to the strong quadrupole interaction between the sulfone moiety and CO
2
molecules, the adsorption of CO on 1 and 2 is highly selective over the adsorption of N and CH 4 [106,107] .
2
2
Furthermore, both frameworks exhibit high chemical and water stability and cyclic regeneration [Figure 7].
This work provides an effective route for the development of functionalized MOFs with high selectivity for
CO capture.
2
The pore windows and pore sizes of MOFs are made up of both organic and inorganic structural blocks.
Therefore, the pore size of MOFs can be adjusted by changing the type of organic and inorganic structural
blocks, allowing the pore structure of MOFs to vary considerably in size, which is one of the key reasons for