Silica materials are used in a wide range of applications such as catalysis, photocatalysis, CO₂ capture, and environmental remediation. These nanomaterials (NMs) have been extensively investigated since the advent of Stöber silica. However, the absence of pores and small surface area of Stöber silica limited its applications. Later, the discovery of MCM-41 type mesoporous silica using surfactants as structural directing agents became revolutionary in the field of silica NMs. This review focuses on the methods used for synthesizing mesoporous silica nanoparticles and their applications in various fields including catalysis (i.e., support for nanoparticle catalysts) and environmental remediation (CO to CO₂ conversion, volatile organic compound (VOC) removal, and CO₂ capture). The current issues/challenges in realizing the practical applications of these conventional materials are also highlighted. This review also compares the characteristics and applications of MCM-41, SBA-15, and KCC-1 to demonstrate the effect of the morphology and pore architecture of silica on the properties of silica-based NMs. The scope for future developments in the synthesis and applications of silica materials with different pore sizes and morphologies is discussed.

We report a facile protocol for the synthesis of fibrous nano-silica (KCC-1) with controllable size and fiber density. In this work, we have shown that the particle size, fiber density, surface area and pore volume of KCC-1 can be effectively controlled and tuned by changing various reaction parameters, such as the concentrations of urea, CTAB, 1-pentanol, reaction time, temperature, solvent ratio and even outside stirring time. For the first time, we were able to control the particle size ranging from as small as 170 nm to as large as 1120 nm. We were also able to control the fiber density from low to medium to very dense, which consequently allowed the tuning of the pore volume. We were able to achieve a pore volume of 2.18 cm³/g, which is the highest reported for such a fibrous material. Notably we were even able to increase the surface area up to 1244 m²/g, nearly double the previously reported surface area of KCC-1. Thus, one can now synthesize KCC-1 with various degrees of size, surface area, pore volume and fiber density.

Hybrid materials by functionalization of fibrous nanosilica (KCC-1) were synthesized for efficient CO₂ capture, using various amine molecules by physisorption (ads.) as well as covalent attachment.

Point source CO₂ capture (PSCC) is crucial for decarbonizing various industrial sectors, while direct air capture (DAC) holds promise for removing CO₂ directly from the air. Sorbents play a critical role in both technologies, with their performances, efficiency, cost, etc., largely depending on which type is used (physical or chemical). Solid amine sorbents (SAS) employed in the chemical adsorption of CO₂ are suitable for both PSCC and DAC. SAS offer significant advantages over liquid amines such as monoethanolamine (MEA), due to their ability to perform cyclic adsorption–desorption with much lower energy requirement. The environmental concern associated with MEA can be mitigated by SAS. Support materials have a significantly important role in stabilizing amine and enhancing stability and kinetics; varieties of support materials have been screened at a laboratory scale. One promising support material is a silica gel (SG), which is commercially available and attractive for designing cost‐effective sorbents for large‐scale CO₂ capture. Various impregnation methods such as physical adsorption and covalent functionalization have been employed to functionalize silica surfaces with amines. This review provided a comprehensive critical analysis of SG‐based SAS for CO₂ capture. We discussed and evaluated them in terms of their adsorption capacity, adsorption, and desorption conditions, and the kinetics involved in these processes. Finally, we proposed a few recommendations for further development of low‐cost, lower carbon footprint SAS for large‐scale deployment of CO₂ capture technology.