Thermocatalytic CO2 conversion by siliceous matter: a review

Abstract

Solid siliceous (silica/silicate) materials can substantially contribute to the strategic decarbonization and defossilization efforts based on carbon capture and utilization (CCU), where CO₂ footprint is mitigated by its capture and conversion into a wide variety of value-added chemical commodities. Targeting CO₂ utilization in particular, siliceous catalysts are widely utilized for thermal conversion of CO₂ due to their tunable porosity and morphology, ideal physiochemical properties such as high thermal resistivity, and ease of preparation by green protocols. In terms of catalytic performance and reactivity (activity, selectivity, and stability), thermocatalytic CO₂ conversion using siliceous-based catalysts is comparable to that with non-precious and precious pure metal–metal oxide catalysts, considering the inert nature of siliceous materials. Hence, in the current review, we focus on the recent advances in CO₂ conversion facilitated by conventional and advanced silica/silicate-based catalysts by reviewing and comparing proof-of-principle experiments on catalyst activity and stability for thermocatalytic CO₂ transformations. From this perspective, initially, we summarize the gas-phase thermocatalytic CO₂ reduction pathways (mainly reforming and hydrogenation) to produce C₁ and C₂₊ chemicals. Thereafter, we specifically outline the advanced design and synthesis techniques for silica/silicate-based catalysts having diverse focal, compositional, and structural features for these reactions. The categorized CO₂ reactions are then examined with respect to different subdivisions including conventional, morphology-defined, structurally-defined, and atomically-defined siliceous-based catalysts. Furthermore, after highlighting their hierarchical and porosity merits for CO₂ transformations, three important routes including CO₂ conversion to hydrocarbons, alcohols, and fine/specialty organic substances using siliceous-based catalysts are exclusively emphasized. Finally, based on our personal perspective, potential areas for improvement and further research opportunities will be proposed.