Abstract
Alkali metal-based silicate sorbents are attracting increasing attention as promising materials for hightemperature CO₂ capture from industrial sources. This review systematizes recent advances in the development and application of lithium (Li₄SiO₄), sodium (Na₂SiO₃, Na₄SiO₄), and potassium silicates for direct CO₂ capture at temperatures of 500-750 °C. Lithium silicates exhibit the highest sorption capacity (theoretical value of 367 mg CO₂ g⁻¹ and practical values of 30-35 wt.%), with an optimal operating temperature range of 550-650 °C and lower regeneration temperatures (700-850 °C) compared to calcium-based analogues. Sorption proceeds via a two-step mechanism: a rapid surface reaction forming Li₂CO₃ and Li₂SiO₃, followed by a diffusion-controlled stage limited by ion transport through the product layer. Nanostructuring and doping with alkali carbonates (K₂CO₃, Na₂CO₃) effectively accelerate diffusion and improve cyclic stability to up to 200 cycles without capacity loss. Doping with transition metals (Ti, Ca) and co-doping with potassium suppress sintering and broaden the temperature window for efficient sorption. The use of industrial wastes (fly ash, metallurgical slags, spent batteries) as precursor sources reduces production costs by 3-20 times. Promising research directions include the development of bifunctional sorbent-catalysts, the application of computational design and machine learning for composition optimization, demonstration of the technology under real industrial conditions, and integration with renewable energy sources. If current challenges are addressed, silicate sorbents may become a key technology for deep decarbonization of energy-intensive sectors and for achieving carbon neutrality.