Silica incorporated MOF for CO2 capture

https://doi.org/10.3390/en15093473

“Aerosil, or fumed silica, is synthetic amorphous silicon dioxide—nonporous 3D material with a high surface area. Like C-containing MOF-composites, SiO₂-containing MOF-composites combine the advantages of two matrices (SiO₂ and MOF), as well as new perspective properties which it can possess due to the synergistic effect. The presence of silica materials can increase the porosity of new materials and provide more active sites, thus promoting the application in adsorption and elsewhere. Moreover, silicas have high stability and can be considered as low-cost materials. Therefore, the combination of MOFs and porous or nonporous silicas can enhance the stability and properties of new composites as well as provide a platform for widespread use [62]. Literature studies indicate that there are several attempts to produce MOF-silica composites, using HKUST-1, MIL-68, MIL-101(Cr), ZIF-8, MOF-5, etc., and SBA-15 [24], MCM-41 [63], MSU, etc., which are described in detail in various reviews [62,64]. Chen et al. have studied HKUST-1 and its composites with different contents of SBA-15 [24] and reported that the interactions between surface silanol groups and metal centers induced structural changes, resulting in an increase in surface area and micropore volume, and inferring from that, the composite with the most optimal SBA-15 content was able to adsorb for almost 16% more CO₂ than pristine HKUST-1. Another study concluded that the adsorbent containing CuBTC and MCM-41 is able to adsorb 20% more CO₂ than MCM-41, and the resulting composite has increased CO₂/CH₄ selectivity [63]. Generally, MOF-silica composites exhibit improved properties that can be attributed to the synergetic effect compared to pristine MOFs and silicas [24,62]. In addition to the already mentioned materials, MOF hybrid sorbents containing various natural materials, such as zeolites, are also being studied. Lestari et al. [65] reported that although the specific surface area of the resulting composite has decreased due to the interaction of Indonesian natural zeolite and CuBTC, it is still able to adsorb 12% more CO₂ than the initial materials.”