The application of high surface area silica (fumed silica) in VOC capture, leveraging its unique nanoporous structure and tunable surface chemical properties, has become an important direction for high-efficiency adsorption materials. Its core advantages lie in adsorption capacity, selectivity, and long-term stability, particularly excelling in the treatment of small-molecule VOCs such as formaldehyde.

Material Characteristics and Structural Advantages
Ultra-high specific surface area: High surface area silica can have a specific surface area of 500–1000 m²/g, and some modified products (such as "Ruishi") can reach more than 30 times the specific surface area of activated carbon after activation, significantly increasing the density of contact points for VOC molecules.
Precise pore size matching: Its pore size distribution is concentrated in the 0.4–0.6 nm micropore range, which highly matches the kinetic diameter of formaldehyde molecules (approximately 0.45 nm), conforming to the size exclusion effect and achieving selective capture.
Surface hydroxyl functionalization: The abundant Si–OH groups on the surface can undergo weak chemical interactions with polar VOCs (such as formaldehyde and acetaldehyde) through hydrogen bonding, enhancing adsorption affinity, distinguishing it from the purely physical adsorption mechanism of activated carbon.
Thermal stability and regenerability: Silica materials are structurally stable below 300°C, and can recover more than 90% of their adsorption capacity after vacuum degassing or low-temperature thermal regeneration (<150°C), making them suitable for long-term low-concentration pollution scenarios.
VOC Adsorption Mechanism
The adsorption process is predominantly physical adsorption, relying on van der Waals forces to capture VOC molecules within the pores, and its kinetics are controlled by pore diffusion. The mesoporous structure can act as a transport channel, accelerating the diffusion of small molecules into the micropores and improving the adsorption rate.
Surface functionalization can introduce chemical adsorption mechanisms:

Amination modification (–NH₂): Reacts with formaldehyde through nucleophilic addition, forming stable imine bonds, achieving irreversible capture, and significantly improving selectivity and capacity. Silane Coupling Agent Modification: Introducing hydrophobic groups can enhance the adsorption of non-polar VOCs (such as benzene and toluene), expanding the application range.
Composite Structure Design:  Combining with MOFs (such as ZIF-8) or graphene can create a "microporous-mesoporous" gradient structure, balancing high capacity and rapid mass transfer.
Performance Comparison with Mainstream Adsorption Materials
Performance Indicator | High Specific Surface Area Silica | Activated Carbon | MOFs (e.g., ZIF-8) | Zeolite
Specific Surface Area (m²/g) | 500–1000 | 800–1500 | 1000–7000 | 300–800
Formaldehyde Adsorption Capacity (mg/g) | 80–150 (after functionalization) | 50–120 | 120–200 | 30–80
Humidity Tolerance | Excellent (hydrophilic surface) | Poor (water competitive adsorption) | Medium (partially easily hydrolyzed) | Excellent (hydrophobic type available)
Regeneration Cycles | >15 times | 5–10 times | 3–8 times (prone to structural collapse) | >20 times
Toxicity and Environmental Friendliness | Non-toxic, inert | May contain heavy metal impurities | Metal-organic frameworks may contain toxic metals | Non-toxic
Cost | Medium | Low | High | Medium
Note: Although silica has a lower absolute adsorption capacity than some MOFs, its overall stability, regenerability, and safety offer greater engineering advantages in the field of civil air purification.

Latest Research Progress (2023–2025)
Functionalized Nanoscale Silica: Research in 2023 confirmed that green nanoscale silica (GNs) synthesized through biomimetic methods can be prepared within 15 minutes, with formaldehyde adsorption efficiency comparable to traditional mesoporous materials, and without secondary pollution. Silicon-based MOF composite materials: A silica-supported ZIF-8 composite adsorbent developed in 2024 combines the ultra-high porosity of MOFs with the mechanical stability of silica, achieving a 40% increase in dynamic formaldehyde adsorption capacity, suitable for continuous flow purification systems.
Smart responsive materials: Aminated silica nanoparticles enable colorimetric sensing of formaldehyde with a detection limit as low as 36 ppb, combining adsorption and real-time monitoring functions.
Practical Application Cases
Industrial waste gas treatment: Used as an auxiliary adsorption unit in combination with cyclone dust collectors and bag filters for the synergistic treatment of dust and trace VOCs in carbon black production, achieving stable outlet concentrations below 10 mg/m³.
Indoor air purification:
Products such as "Ruishi" use high specific surface area silica as the core adsorbent, applied in children's rooms and nurseries, achieving a formaldehyde removal rate of over 90% in 72 hours in actual tests.
Combined with activated carbon fibers to form filter elements for in-car air purifiers, effectively reducing the concentration of benzene compounds released from leather and PVC.
Building integrated materials: Functionalized carbon black is incorporated into coatings and wallpaper substrates to achieve "passive" continuous VOC adsorption, extending the purification cycle.