Mesoporous Silica-Supported MOF Composites for CO₂ Capture: Fabrication, Synergistic Effects, and Limitations

The continuous rise in atmospheric carbon dioxide (CO₂) concentration poses a severe challenge to the global climate, creating an urgent need for the development of efficient, stable, and economically viable carbon-capture technologies. Metal-organic frameworks (MOFs), with their ultra-high specific surface area and tunable pore architecture, have demonstrated significant potential for CO₂ adsorption. However, single MOF materials are typically constrained by limitations such as high mass transfer resistance, poor hydrothermal stability, and difficulties in processing their powdered form. Coupling MOF with ordered mesoporous silica (MS) to construct hierarchical MOF@MS composite materials has been proven to be an effective strategy for overcoming these shortcomings. This review systematically summarizes the recent research progress on mesoporous silica-supported MOF composite materials for CO₂ capture. First, an architecture-based taxonomy is established in which every composite is assigned according to five decision rules-nucleation site, synthesis sequence, spatial arrangement of the two phases, interfacial bonding, and the intended role of the mesoporous silica-and six architecture classes are distinguished; systems that lack either a crystalline MOF phase or a siliceous mesoporous phase (MOF-on-MOF hybrids, wood-supported MOF, and amine-loaded silica) are explicitly excluded from the comparative analysis. Second, the principles, advantages, and drawbacks of the individual preparation routes, including in situ growth, confined growth, layer-by-layer assembly, post-synthetic assembly, selective etching, physical mixing, and macroscopic shaping, are discussed in detail and mapped onto that taxonomy. Third, the multiple synergistic adsorption mechanisms between mesoporous silica and MOF are deeply analyzed, encompassing the optimization of mass transfer by hierarchical pore structures, the enhancement of active site accessibility and stability through interfacial bonding, and the improvement of CO₂ selectivity via functional group modification. On this basis, this review objectively examines the core challenges and limitations currently faced in this field, such as pore blockage, weak interfacial interactions, performance degradation under realistic flue-gas conditions (containing moisture and impurities), and high costs associated with large-scale preparation. Finally, to address these issues, future research directions are proposed from five perspectives: developing novel stable composite materials, optimizing green scalable synthesis processes, deepening multi-scale theoretical simulations, establishing standardized evaluation systems oriented toward realistic operating conditions, and exploring multifunctional integrated and stimuli-responsive materials. This review aims to provide focused and systematic guidance for the rational design of next-generation MOF@MS adsorbents for CO₂ capture with high performance, low cost, and enhanced stability by elucidating the specific structure-performance mechanisms and practical limitations that are frequently overlooked in general surveys.