Synthesis of novel core-shell structured solid amine adsorbents and their CO₂ capture performance

In recent years, immense attention is attracted by the implementation of amine functionalized solid adsorbents for direct air capture (DAC) of CO₂. However, a great reduction of pore volume and specific surface area within the adsorbents is led to by the amine functionalization of traditional supports (such as SBA-15). In the context of DAC, the CO₂ adsorption dynamics is significantly limited by the extremely low partial pressure of CO₂ (400×10⁻⁶), thus with lower CO₂ adsorption capacity. To address this issue, silica hollow spheres (RHMS-4) with large pore aperture and high structural tunability are prepared by using phenolic resin microspheres as templates and adjusting the mass fraction of tetraethyl orthosilicate (TEOS) with the introduction of a reaming agent. The amine functionalization is achieved by impregnating silica support in tetraethylenepentamine (TEPA) solution. The structure-performance relationship of RHMS-4-TEPA series adsorbents is investigated by XRD, FT-IR, and other characterization techniques. The effect of amine content, adsorption temperature and ambient humidity on the CO₂ adsorption capacity are also investigated. The experimental results show that: Under dry condition (50 ℃ and 400×10⁻⁶ CO₂), the adsorption capacity of RHMS-4-TEPA₇₀ reach to about 2.400 mmol/g, while the CO₂ uptake is improved by about 42% with the presence of moisture. After 10 sorption-desorption cycles, relatively high CO₂ adsorption capacity and excellent cycling stability are still maintained by RHMS-4-TEPA₇₀.