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

Figure 1. Three basic routes (post-combustion capture, pre-combustion capture, and oxy-fuel combustion) of CO capture in industry.
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on burning fossil fuels in oxygen-rich gases to obtain high concentrations of CO , which is direct
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sequestration and utilization. Due to the removal of N in the air, the volume of combustion gas is reduced,
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so the volume of flue gas produced after combustion is reduced to 1/5-1/3 of that of conventional coal-fired
boilers. Meanwhile, the concentration of CO in the flue gas is high, making the cost of capturing CO
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lower. However, this technology is not ideal for CO capture due to its high energy consumption and
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investment costs [30,31] . Post-combustion capture means capturing CO in the flue gas from the combustion
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emissions. Since the partial pressure of CO after capture is low, it is necessary to pressurize the CO before
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storage, which increases the operating cost. Even so, post-combustion capture has the following advantages
over other capture techniques: (1) A wide range of applications. Post-combustion capture technology can
not only separate CO from flue gas but also capture NO and SO to achieve the purpose of denitrification
X
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X
and desulfurization; (2) Strong applicability. The trapping device is installed in the flue gas tail of the power
plant, which has no influence on the existing power generation equipment and; (3) Relatively mature
development and flexible operation [32-34] . Therefore, post-combustion capture is a common CO capture
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technology.
In addition, CO capture technology can be classified based on different capture methods, including
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chemical absorption , membrane separation [36-38] , biological immobilization , adsorption [40-43] , and other
[35]
[39]
approaches. Among them, the adsorption method is the most competitive CO capture technique.
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CO capture adsorbent
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Adsorption is the uptake of molecules or ions from the surrounding liquid or gas by the surface of a solid
substance. The adsorption method has been widely studied by scholars for its advantages of low cost and
simple operation . However, its practical application requires the design and synthesis of an easily
[44]
regenerated and durable adsorbent material. Generally speaking, a suitable CO adsorbent needs to have
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high selectivity and adsorption capacity, adequate adsorption/desorption kinetics, stability after several
adsorption/desorption cycles, and good chemical and mechanical stability.

Among many CO adsorbents, porous solid adsorbents have good application prospects because of their low
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adsorption enthalpy and easy recycling. The traditional porous adsorbents for CO capture mainly include
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activated carbon, zeolite, silica gel, activated alumina, and so on [45-48] . Zeolite, a common solid adsorbent, is a