The Importance of Precursors and Modification Groups of Aerogels in CO2 Capture

Abstract

The rapid growth of CO2 emissions in the atmosphere has attracted great attention due to the influence of the greenhouse effect. Aerogels’ application for capturing CO2 is quite promising owing to their numerous advantages, such as high porosity (~95%); these are predominantly mesoporous (20–50 nm) materials with very high surface area (>800 m2∙g−1). To increase the CO2 level of aerogels’ uptake capacity and selectivity, active materials have been investigated, such as potassium carbonate, K2CO3, amines, and ionic-liquid amino-acid moieties loaded onto the surface of aerogels. The flexibility of the composition and surface chemistry of aerogels can be modified intentionally—indeed, manipulated—for CO2 capture. Up to now, most research has focused mainly on the synthesis of amine-modified silica aerogels and the evaluation of their CO2-sorption properties. However, there is no comprehensive study focusing on the effect of different types of aerogels and modification groups on the adsorption of CO2. In this review, we present, in broad terms, the use of different precursors, as well as modification of synthesis parameters. The present review aims to consider which kind of precursors and modification groups can serve as potentially attractive molecular-design characteristics in promising materials for capturing CO2.

Valorization of Starch to Biobased Materials: A Review

“…Aerogel is a solid, ultra-lightweight substance with high porosity and other exceptional features [ 180 ]. It consists of a three-dimensional and very porous network created from organic, inorganic, or mixed precursors utilizing a sol-gel approach paired with quick-drying technology to extract the liquid in an alcogel and replace it with another liquid [ 181 , 182 ]. However, in a more generic term, any non-fluid colloidal network or polymer network that is enlarged across its entire volume by a fluid could be referred to as aerogels.…”

“…The purpose of drying solid materials is to remove moisture from their pores, which would otherwise cause the silica framework to cave in and succumb, causing the gel structure to collapse completely [ 204 ]. Among the numerous drying methods, such as supercritical drying, ambient-pressure drying, freeze-drying, vacuum drying, and microwave drying, as reported in the literature [ 181 ], only three drying methods (freeze-drying, ambient air (pressure) drying, and supercritical carbon dioxide) have been used for the drying of gel-like materials [ 205 ]. Nevertheless, freeze-drying and supercritical carbon dioxide are preferred because they do not harm the underlying microstructure of aerogels [ 181 ].…”

“…Among the numerous drying methods, such as supercritical drying, ambient-pressure drying, freeze-drying, vacuum drying, and microwave drying, as reported in the literature [ 181 ], only three drying methods (freeze-drying, ambient air (pressure) drying, and supercritical carbon dioxide) have been used for the drying of gel-like materials [ 205 ]. Nevertheless, freeze-drying and supercritical carbon dioxide are preferred because they do not harm the underlying microstructure of aerogels [ 181 ]. Meanwhile, evaporation could also be regarded as a drying process for gels [ 204 ].…”

Manufacturing silica aerogel and cryogel through ambient pressure and freeze drying

“…The freeze-drying (FD) method could potentially avoid damage to the 3D solid network that is formed during condensation. 11 The fundamental reason for this is the absence of the phase boundary between liquid and gas phase that typically occurs when ambient pressure drying (APD) is used, hence resulting in no capillary forces being present within the pores. Cryogels are produced using the FD methodology, during which the liquid within the pores of the wet gel is initially frozen and subsequently removed by sublimation under vacuum conditions.…”

The AEROPILs Generation: Novel Poly(Ionic Liquid)-Based Aerogels for CO2 Capture

“…Aerogels have low density, high specific surface area, high porosity, a tailorable surface functionality, and good sorption capacity [ 10 , 11 , 12 , 13 , 14 , 15 ]. They are currently in the market and under research for multiple applications such as thermal insulation, metal-ion sorption, filtration and separation, oil-water separation, drug delivery, catalysis, and CC [ 12 , 16 , 17 , 18 ]. Recent research on aerogels for CC focused on tailoring their physicochemical properties, which is exemplified by amine modified SiO 2 aerogels using (3-aminopropyl)triethoxysilane (APTES), polyethyleneimine (PEI), and tetraethylenepentamine (TEPA) [ 19 , 20 , 21 , 22 ].…”