Durable and High-Efficiency Air Filtration by Superamphiphobic Silica Composite Aerogel

Abstract

The escalating industrial emissions have dramatically increased airborne particulate matter (PM), particularly submicron particles (PM0.3), creating substantial health risks through respiratory system penetration. Current fiber-based filtration systems predominantly relying on electrostatic adsorption mechanisms suffer from critical limitations, including insufficient efficiency, potential secondary contamination, and performance degradation in humid environments. We develop a flexible silica composite aerogel to overcome these challenges with customizable and exceptional superamphiphobicity. This composite aerogel exhibits high porosity of ~95% and robust compression Young’s modulus that reaches ~220 kPa at 50% strain even after 1000 cycles. These features enable it to maintain a high filtration efficiency of ~98.52% for PM0.3, even after 50 cycles under traditional artificial simulation conditions. Significantly, a competitive filtration efficiency of ~97.9% is still performed in our composite aerogel at high humidity (water mist), high temperatures (50–250 °C), and corrosive solutions or atmospheres environments, revealing potential industrial applications. This work is expected to replace conventional air filtration materials and pave the way for various human protection and industrial production applications.

1. Introduction

Air pollution directly causes over 6.3 million deaths annually [1]. Among pollutants, particulate matter (PM) is the primary culprit, often termed the “No. 1 killer” of human health. PM0.3, with a diameter of less than 0.3 μm, is particularly dangerous as it can penetrate lung tissues and enter the bloodstream directly [2,3,4,5]. It significantly increases the incidence of high-risk diseases, including cancer, cardiovascular disease, diabetes, and Alzheimer’s disease [6,7,8,9]. Given these threats, fabric filters such as masks and filter cotton are in high demand to prevent air pollutants from entering the respiratory system and to protect human health [10,11]. However, achieving highly precise and sustainable filtration remains a significant challenge due to several limitations of these materials: moisture absorption, low porosity, and large fiber diameters and pore sizes [12,13,14]. The enhancement of electrostatic adsorption of fibers is a feasible strategy to slow down the loss of filtration precision, it is inherently limited and often exacerbates the problem by making it more challenging to remove adhered pollutants. This leads to unsustainable use and secondary pollution [15,16].

Moreover, PM0.3 primarily originates from high-temperature sources such as automobile exhaust (70–80 °C), factory emissions (120–200 °C), and fossil fuel combustion (70–200 °C), which also release large amounts of corrosive particles [17,18,19,20]. These sources impose stringent requirements on filtration materials, as most existing filters are only effective in one environment. For instance, fiber-based filters are prone to cracking or melting at high temperatures [21]. In contrast glass-, ceramic-, and metal-based filters, despite their excellent thermal stability, are vulnerable to corrosion by acids or alkalis [22]. Therefore, there is an urgent need for a filtration material that combines high filtration efficiency, sustainability, and recyclability, and can operate effectively across diverse and harsh environments.

Aerogels are emerging as promising candidates for air filtration materials due to their large porosity, low density, high specific surface area, and excellent multi-environment serviceability [23,24]. For instance, a nanofiber aerogel filter assembled from natural silk nanofibers (SNFs) and polyvinyl alcohol (PVA) via freeze-drying achieved a filtration efficiency of 98% for PM10 [25]. Another example is a metal-organic framework (MOF)-decorated polyimide nanofiber aerogel, which demonstrated a filtration efficiency of 96.2% for PM0.3 at 300 °C, with a pressure drop of only 88.5 Pa [26]. Additionally, an aerogel filter combining hydrophobic Si-O-Si binders with electrostatically spun silica nanofibers and bacterial cellulose nanofibers achieved a filtration efficiency of 97% for PM0.3, with a pressure drop of 189 Pa [27]. These examples highlight the potential of aerogels to achieve high filtration efficiency while maintaining low-pressure drop and multi-environment serviceability. However, developing aerogel filters with even higher efficiency, sustainability, mild preparation conditions, and robust performance across diverse environments remains a critical challenge and an important future direction infiltration.

Herein, we introduce a novel, customizable, flexible, superamphiphobic, and reusable silica composite aerogel filter named SAMS, prepared via simple atmospheric pressure drying followed by fluorination. The near-zero shrinkage of the silica aerogel from sol to fluorination ensures its customizability and high porosity, enabling it to fill confined spaces fully. The synergistic combination of silica aerogel and melamine sponge endows the filter with excellent flexibility and, most importantly, long-lasting compressive properties. These unique features enable the SAMS filter to achieve a high filtration efficiency of ~98.52% for PM0.3, even after 50 cycles. Moreover, it performs well in complex environments, such as high humidity, high temperature, and corrosive solutions. Following these advantages, the SAMS filter is supposed to be a strong competitor for traditional commercial filters, including N95 filter cotton, N95 masks, surgical masks, and filter paper, and to lead the development trend of the next generation of filtration products.

2. Materials and Methods

2.1. Materials

The melamine sponge was purchased from Anyin Acoustic Materials Factory. Methyltrimethoxysilane (MTMS) was supplied by Shanghai Aladdin Biochemical Technology Co., Ltd, Shanghai, China. Cetyltrimethylammonium bromide (CTAB), anhydrous ethanol (EtOH), ammonia (NH₄OH), and acetic acid (HAc) were obtained from Chengdu Cologne Chemical Co. 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (PFDTES) was procured from Quanzhou Sikang New Material Development Co. All chemicals were used as received without further purification. Deionized water, produced in-house, was utilized throughout the experiments. The filter paper was provided by Donaldson Filter Paper Co., Ltd, Hongkong, China. Commercially available products, including N95 masks, surgical masks, N95 filter cotton, edible oil, vinegar, tea, and coffee, were sourced from local markets.

The silica aerogel was prepared as follows. First, 0.05 g of CTAB was dissolved in 35 mL of deionized water and stirred in a constant-temperature water bath at 35 °C for 5 min. Subsequently, 10 mL of MTMS was added, and the mixture was stirred for 30 min until complete hydrolysis occurred. The pH value was adjusted to 10–11 using a 0.5 mol/L NH₄OH solution to obtain the sol. The sol was immediately filled into the melamine sponge and aged at 35 °C for 24 h. The excess water was replaced with anhydrous ethanol at 60 °C for 24 h and then at 80 °C for 12 h. Finally, the sample was dried at 90 °C for 24 h to obtain the silica composite aerogel. The aerogel was treated with a PFDTES/NH₄OH/EtOH solution in a volume ratio of 1:1:100 and dried at 60 °C for 3 h to prepare the SAMS filter.

2.2. Characterization

The morphology was characterized by scanning electron microscopy (SEM, ZEISS Sigma 300, Oberkochen, Germany) under an accelerating voltage of 3 kV. The pore structure was assessed using a physical adsorption analyzer (BJH, Quantachrome Nova 4000e, Florida, USA). The specific surface area was obtained by the Brunauer–Emmett–Teller (BET) method. The mechanical properties of the materials were tested using an electronic universal testing machine (CMT6103, China). The surface chemistry was analyzed by X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha, Waltham, MA, USA). The chemical structure of the fluorine-modified aerogel was characterized via FT-IR spectroscopy (Thermo Fisher Scientific Nicolet iS20, USA). The apparent contact angle of water and oil (≈6 μL) was measured using a DSA 30 contact angle meter in a laboratory environment with a relative humidity of ≈ 50%. The material’s thermal stability was evaluated using a simultaneous thermal analyzer (TG-DSC, TA SDT 600, (TA Instruments, New Castle, DE, USA) with a ramp rate of 10 °C/min from 30 to 800 °C under N₂ protection. Time-lapse photographs and video portions were captured using a Photron FASTCAM Mini UX 100 high-speed camera equipped with a Navitar 6000 zoom lens. The video’s other optical photographs and portions were captured using a Nikon D3400 digital camera equipped (Nikon Corporation, Tokyo, Japan) with a Navitar 6000 zoom lens (Navitar, Inc., Rochester, NY, USA).

2.3. Test Method

The droplet impact test was performed at room temperature on an optical platform and was recorded by a high-speed video camera. Then, 6 μL of water/oil droplets were extruded through a syringe and were allowed to fall freely from a height of 5 mm. The high-humidity environment was created by mixing water vapor from humidifiers with smoke. The acidic and alkaline environment was established by leveraging the volatile properties of ammonia and acetic acid. These were introduced into a sealed chamber with filtration devices to simulate atmospheric pollutant interactions. The experimental platform for filtration performance was constructed using three special borosilicate glass bottles (Figure S14). The PM in the experiment was generated by burning the aromatherapy because burning produced a large amount of particulate matter and oily substances, which could simulate the composition of air pollutants. The PM concentration was measured by two dust particle counters (NK-800). The filtration efficiency was calculated as follows:

$$\begin{array}{c}\mathsf{\eta }={\displaystyle \frac{{\mathrm{C}}_1{-\mathrm{C}}_0}{{\mathrm{C}}_0}}\times 100\%\end{array}$$

(1)

where C₀ and C₁ were the concentrations of particles before and after they passed through the filter material, respectively. The pressure drop was measured using a differential pressure gauge (Testo-510 Dettol). Quality factor (QF) was an essential index for evaluating the performance of filter materials. QF was related to the filtration efficiency and pressure drop of the material; the higher the QF, the better the comprehensive filtration performance of the material. The quality factor was calculated as follows:

$$\begin{array}{c}\mathrm{Q}\mathrm{F}={\displaystyle \frac{-\ln \left(1-\mathsf{\eta }\right)}{∆\mathrm{P}}}\end{array}$$

(2)

where η represents the filtration efficiency, ∆P represents the pressure drop.

3. Results

3.1. Fabrication and Key Characteristics of SAMS

Figure 1a demonstrates the evolution process for preparing customizable and superamphiphobic silica composite aerogel. This process was accompanied by hydrolyzation of methyltrimethoxysilane (MTMS), pouring sol, gel, seal aging, solvent replacement, ambient pressure drying, and fluorination (Figure S1). Notably, the silica composite aerogels exhibited near-zero shrinkage (<1%), primarily attributed to the nonpolar nature of the nonhydrolyzable methyl groups in the MTMS precursors. These nonpolar methyl groups significantly reduce the affinity of polar molecules such as alcohols and water for the gel pores, resulting in a negligible effect of capillary pressure on gel shrinkage during solvent evaporation [28]. The nonpolar and nonhydrolyzable methyl groups also impart hydrophobicity to the gel network, producing a rebound effect that effectively inhibits gel shrinkage [29]. As the seal aging time increased from 0 to 24 h, the particle size gradually decreased, and the main chain structure became more robust, further contributing to the near-zero shrinkage (Figures S2 and S3) [30].

Silica composite aerogel was treated with a mixed PFDTES/ammonia/EtOH solution to confer oil resistance, transitioning the aerogels to superoleophobic. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses confirmed the successful grafting of PFDTES onto the silica particles (Figure S4). The synergistic effect of MTMS and the successful grafting of PFDTES gives the aerogel superamphiphobicity properties, which is a critical factor for the filtering essential prerequisite for the durable use of the filtration material in humid environments and the filtration of oily particles. Results showed that water and oil droplets rapidly rebound from the SAMS surface without spreading or wetting, maintaining repellency even for liquids with varying surface tensions (Figure S5). Notably, no liquid droplets remained on the surface after immersion in water and oil, and no wetting was observed (Movie S1). These excellent performances give SAMS excellent self-cleaning and antifouling properties. Notably, owing to the near-zero shrinkage of the prepared silica aerogel, large filter materials with dimensions of 32 cm × 22 cm × 0.1 cm were successfully fabricated by simply scaling up the dimensions of the molding molds (Figure 1b and Movie S2). This demonstrates the material’s significant potential for large-scale production.

To investigate the effect of the fluorination strategy on the structural properties, we compared and analyzed the scanning electron microscopy (SEM) images of SAMS before and after fluorination (Figure S6 and Figure 1c). Results show that, due to the high porosity of the melamine sponge (Figure S7), silica aerogel can completely fill its interior. We found that both the silica aerogel and the melamine sponge are tightly encapsulated, with the silica aerogel evenly distributed around the melamine sponge skeleton. This indicates that the fluorination strategy did not affect the structure of SAMS. By enlarging the SEM image of SAMS (Figure S8), it can be seen that the filled silica aerogel was composed of nanoparticles of different sizes, forming many uniform and irregular nanoporous structures. This open and mutually supporting structure provides sufficient channels for airflow, ensuring good air permeability for SAMS (Movie S3).

Additionally, the air filter material’s specific surface area and pore size were critical determinants of filtration performance. SAMS exhibited a low pore size and a specific surface area of 118.75 m²/g, which enhanced its particulate matter capture efficiency (Figure 1d). The adsorption-desorption curve corresponded to the type IV adsorption-desorption isotherm in the IUPAC classification, indicating favorable characteristics and uniformity for the surface and pore structure [31]. Figure 1e illustrates that the SAMS filter significantly outperforms commercial filter materials in key performance metrics, including filtration efficiency, thickness, durability, quality factor (10th cycle), temperature resistance, and usage environment. For more details, please refer to Figure S9. Additionally, the SAMS filter benefited from its low bulk density (0.14 g/cm³), resulting in a piece of the same size as N95 filter cotton weighing 0.1907 g less, enhancing wear comfort (Figure 1f). Further, due to its high material utilization rate, the SAMS filter exhibited significantly lower production costs than N95 filter cotton (Table S1).

3.2. Mechanical Properties and Thermomechanical Stability of SAMS

In practical applications, excellent mechanical properties are essential for filter materials. The synergistic effect of the melamine foam skeleton and silica aerogel significantly enhances the mechanical properties of SAMS, mainly due to the increase in energy dissipation pathways of fine network structure. Figure 2a illustrates that the compression stress–strain (σ–ε) curve of SAMS exhibited a closed loop and three typical compression stages. In the initial stage, when the strain was less than 20%, elastic deformation occurred, indicating elastic bending of the SAMS skeleton. The platform stage persisted until the strain reached 65%, which could be attributed to the compression of the spaces between the SAMS pores. When the strain exceeds 65%, a nonlinear region with a sharp increase in stress is observed, indicating the densification of the SAMS structure. A maximum strain of 80% was achieved under an applied stress of 1.9 MPa, demonstrating the high compressibility of SAMS. Meanwhile, the fatigue resistance of SAMS was evaluated by performing 1000 load–unload cycles at 50% of the maximum radial strain (Figure 2b and Figure S10). During the compression process, the relative height, Young’s modulus, and maximum stress only decreased sharply during the first 30 cycles and then stabilized, which proved its sturdy structure and high compressive strength (Figure 2c). Additionally, after cyclic testing, localized deformation of the aerogel skeleton resulted in partial detachment from the scaffold, thereby reducing the relative height and compressive stresses (Figure S11). The above results indicate that SAMS has good resilience and fatigue resistance.

In industrial filtration applications, the temperature resistance of the filter material is a critical parameter, as it is subjected to prolonged exposure to high-temperature particles. Figure 2d illustrates that SAMS retains excellent mechanical properties and compression resilience after heating at 150 °C and 250 °C for 120 min. Thermogravimetric (TG) analysis further confirmed that SAMS exhibits excellent thermal stability. For more details, please refer to Figure S12. Compared to other aerogels, SAMS withstood significantly higher compressive stress under identical compression conditions (Figure 2e) [27,32,33,34,35,36]. The flexibility of materials also plays a crucial role in enhancing their usability across diverse environments. Figure 2f illustrates that the curved SAMS surface exhibited no cracks and immediately reverted to its original shape upon unfolding. After 1000 folding cycles, its tensile strength and elongation at break remained superior to melamine foam’s (Figure 2g and Figure S13). Similarly, SAMS retained excellent tensile strength and significant elongation at break after being heated at 150 °C and 250 °C for 120 min (Figure 2h). The above results show that the combination of rigidity and flexibility of silica aerogel and melamine sponge gives SAMS excellent compression resistance, flexibility, and environmental adaptability.

3.3. Filtration Performance of SAMS in Traditional Artificial Simulation Environments

We initially evaluated the filtration performance of SAMS at room temperature and a humidity of 35 ± 5% (with a test duration of typically 3 min). This study was conducted on a custom-built test bench in the laboratory (Figure S14). Smoke was drawn into the filter bottle from a smoke bottle using a vacuum pump. At the same time, a gas flowmeter regulated the airflow velocity through the filter (Figure 3a). Additionally, to gain a more comprehensive understanding of the filtration performance of SAMS, we incorporated widely used commercial filter materials, specifically N95 filter cotton and N95 masks, into our comparative analysis. First, the correlation between filtration performance and airflow velocity was examined. Figure S15a illustrates that as airflow velocity increases, the filtration efficiency of SAMS−3mm exhibited minor fluctuations but consistently remained above 97.94%, comparable to that of N95 filter cotton and N95 mask. The filtration efficiency of SAMS−1mm also remained above 85%. For PM2.5, SAMS−3mm and SAMS−1mm achieved filtration efficiencies of 99.36% and 98.97%, respectively (Figure S15b).

Meanwhile, the pressure drop increased linearly with increased airflow velocity (Figure S15c), and the negative effect of airflow velocity on filtration efficiency and pressure drop resulted in a significant decrease in quality factor (Figure S15d,e), a phenomenon consistent with Darcy’s law. SAMS exhibit excellent filtration performance for both PM0.3 and PM2.5 at various airflow velocities, primarily due to their unique nanoporous structure. This structure not only provides abundant pathways for airflow, significantly reducing airflow resistance but also increases the contact rate between particles and the material, thereby enhancing the likelihood of particle capture. Additionally, its nanoscale pore size ensures high filtration precision, enabling it to capture PM0.3 and PM2.5 particles efficiently. The low filtration efficiency of SAMS−1mm is due to the small thickness, which results in a shorter residence time of the particles inside, reducing the chance of inertial collision of the particles and, therefore, the chance of particle trapping. Meanwhile, a long-term filtration test was conducted for over 60 min to investigate the stability of SAMS’s filtration performance. Figure 3b and Figure S16 illustrate that after long-term filtration, the filtering efficiency for PM0.3 and PM2.5 of SAMS−3mm (92.10%, 98.66%) and SAMS−1mm (68.34%, 92.49%) was significantly higher than that of N95 filter cotton (42.76%, 88.09%) and N95 mask (11.47%, 59.99%), demonstrating the excellent durability of SAMS materials. This excellent durability is mainly due to the inclusion of melamine sponge, which improves the brittleness of silica aerogel, giving SAMS the flexibility to withstand the constant impact of airflow and particles during long-term filtration. Meanwhile, optical photographs (Figure S17) and SEM images (Figure S18) revealed that N95 filter cotton and N95 mask were wholly penetrated by oily particles, with their fibers entirely coated with particulate matter, explaining the reduced filtration efficiency. In contrast, SAMS−3mm and SAMS−1mm surfaces were covered with captured particulate matter but retained open pores for airflow and further particle capture (Figure S19). Consequently, SAMS demonstrates a more stable filtration performance compared to N95 filter cotton and N95 mask.

Most commercially available filter materials, such as N95 filter cotton and N95 masks, are disposable and cannot be reused, posing a significant environmental burden. Therefore, the development of reusable filter materials represents a promising future direction. As a filter material with excellent self-cleaning properties, SAMS enables water droplets to roll off its surface, effectively carrying away captured dust particles (Figure S20). Figure 3c illustrates that washing with water significantly weakened the electrostatic effect of the N95 filter cotton and the N95 mask, sharply reducing their filtration efficiency until they became ineffective [37]. In contrast, the filtration efficiency, pressure drop, and quality factor of SAMS−3mm (99.58%, 60 Pa, 0.091 Pa⁻¹) and SAMS−1mm (82%, 18 Pa, 0.095 Pa⁻¹) for PM03 remained stable after 10 filtration cycles (each lasting 10 min). Notably, the filtration efficiency of the SAMS−3mm still reached 98.52% after 50 cycles. Meanwhile, SAMS−3mm and SAMS−1mm also showed good stability in filtration efficiency for PM2.5 after multiple filter cycles (Figure S21). Optical photographs showed that even after prolonged filtration, no fine oil droplets remain on the surface of SAMS−3mm and SAMS−1mm after long-term filtration (Figure S22), which proves that water cleaning not only effectively removes particulate matter from the surface but also reduces the aggregation of oil-containing particles and ensures that their orifices are transparent, thus guaranteeing reusability.

Compared with most aerogel filter materials reported in recent literature, SAMS−3mm and SAMS−1mm exhibited lower pressure drops and higher quality factors for PM0.3 (Figure 3d) [26,27,38,39,40,41,42,43]. Additionally, we utilized the Tyndall effect to evaluate the filtration efficacy of SAMS−3mm, N95 filter cotton, and N95 mask. Figure 3e illustrates significant Tyndall phenomena observed at 21 and 18 min for N95 filter cotton and N95 mask, respectively, indicating successful particulate penetration. In stark contrast, SAMS showed no signs of particulate penetration even after 90 min filtration testing, which is another strong indication of its superior stability. For more details, please refer to Movie S4. These results collectively indicate that SAMS possesses superior structural stability, durability, and reusability.

Benefiting from the excellent machinability of SAMS, we customized a replaceable filter unit for a commercial purifier as a proof-of-concept to explore potential commercial applications (Figure 4a). Figure 4b illustrates that a smoke cake was lit inside a sealed chamber to simulate the release of many air pollutants. Subsequently, the commercial purifier equipped with the SAMS replacement filter was activated, achieving a PM2.5 removal rate of 99% within 6 min (Figure 4c). Meanwhile, SAMS reduced the PM2.5 concentration to 0.04 μg/L within 10 min, demonstrating its superior purification performance (Figure 4d and Movie S5). Additionally, to evaluate the antimicrobial properties of SAMS, we conducted an antibacterial test using Escherichia coli. After 18 h of incubation, the removal rate of E. coli by SAMS reached 90%, indicating its excellent antimicrobial efficacy. For more details, please refer to Figure S23. These results collectively demonstrate that SAMS has broad commercial prospects.

3.4. Filtration Performance of SAMS in Extreme Environments

Considering the practicality of the application, SAMS was exposed to outdoor conditions for 240 days. During this period, no significant changes in its appearance were observed, and it retains its excellent superhydrophobicity (Figure 5a) and filtration performance (Figure 5b). These findings demonstrate the remarkable weather resistance of SAMS.

Its performance in high-humidity environments (water mist) was assessed to further evaluate the stability and durability of SAMS filtration under varying application scenarios. Figure S24 illustrates that SAMS retains its excellent superamphiphobic properties even in high-humidity environments, thereby supporting efficient filtration. First, the stability of SAMS in high-humidity environments was evaluated. Figure S25a illustrates that the filtration efficiency of SAMS−3mm remained at 97.03% at a 1.25 LPM airflow velocity, surpassing that of SAMS−1mm (82.4%), N95 filter cotton (96.82%), and N95 mask (94.01%). For PM2.5, SAMS−3mm and SAMS−1mm achieved filtration efficiencies of 98.91% and 98.38%, respectively (Figure S25b). Additionally, the pressure drop does not change significantly compared to traditional artificial simulation environments (Figure S25c). The quality factor results are illustrated in Figure S25d,e. SMAS exhibits excellent filtration efficiency in high-humidity environments, mainly due to its superamphiphobic properties. On the one hand, the material is not affected by moisture intrusion, which could cause wetting failure. On the other hand, it can capture particulate matter contained in water droplets, thereby improving filtration efficiency.

Meanwhile, the durability of the filter in high-humidity environments was also evaluated. Figure 5c illustrates that after long-term filtration, the filtration efficiency of SAMS−3mm (92.48%) and SAMS−1mm (72.51%) was significantly higher than that of N95 filter cotton (46.77%) and N95 mask (19.16%). For PM2.5 (Figure S26), SAMS−3mm (98.77%) and SAMS−1mm (93.74%) also outperformed N95 filter cotton (91.23%) and N95 mask (22.08%). Optical photographs taken after filtration revealed that the N95 filter cotton and N95 mask were thoroughly permeated by oil-water particulate matter, further explaining the decrease in filtration efficiency (Figure S27). In contrast, the surfaces of SAMS−3mm and SAMS−1mm retained a significant number of liquid droplets on the front side, with no permeation observed on the back side, demonstrating their effectiveness in capturing water-rich particulate matter. Results showed that the filtration efficiencies of all filter materials in the high humidity environment were improved over the traditional artificial simulation, which could be attributed to the fact that some of the particles combined with water to form larger particle clusters, increasing the interception rate of the particulate matter. These experimental results show that SAMS exhibits excellent stability and durability under high-humidity conditions, with its filtration efficiency and pressure drop remaining almost unaffected by humidity. This underscores the significant advantages of SAMS as a high-performance filter material.

As previously mentioned, most particulate matter (PM) originates from factory exhaust, vehicle emissions, and fossil fuel combustion, which contain high-temperature particulate matter. These particles are typically filtered using bag filters. The filter materials for bag filters commonly consist of polyester, nylon, and polypropylene chemical fibers, with a service temperature range of 120–150 °C, making them suitable only for general flue gas treatment [44]. To investigate the high-temperature resistance of filter materials, samples were subjected to temperatures of 50 °C, 100 °C, 150 °C, 200 °C, and 250 °C in a muffle furnace for 120 min each. Under these conditions, N95 filter cotton and N95 mask exhibited noticeable deformation after heat treatment at 150 °C (Figure S28). In contrast, SAMS showed no significant changes in appearance, compressive strength (Figure 2d), tensile strength (Figure 2h), and water/oil contact angle (Figure S29) even after heat treatment at 250 °C, demonstrating its excellent thermal stability. These results support the high filtration efficiency of SAMS under high-temperature conditions. As illustrated in Figure 5d, N95 filter cotton and N95 mask exhibited significant deformation after exposure to 150 °C, leading to a sharp decline in filtration efficiency (<50%). In contrast, even at a heat treatment temperature of 250 °C, SAMS−3mm, and SAMS−1mm filtration efficiencies remained at 98.13% and 80.39%, respectively. For PM2.5, SAMS−3mm, and SAMS−1mm filtration efficiencies remained at 99.6% and 98.13%, respectively (Figure S30).

In practical applications, the corrosion resistance of the material is also critical. As illustrated in Figure S31, after immersion in corrosive solutions of varying pH for 168 h, some fibers in the N95 filter cotton and N95 mask exhibited bending, while SAMS remained unchanged. Furthermore, SAMS retains its superamphiphobic properties (Figure S32). After immersion in corrosive solutions, the filtration efficiency of SAMS−3mm remained above 98.69%, which is superior to that of SAMS−1mm (87.42%), N95 filter cotton (<98.58%), and N95 mask (<41.83%), as illustrated in Figure 5e. For PM2.5, SAMS−3mm and SAMS−1mm also exhibited excellent filtration performance (Figure S33). To evaluate the filtration performance of SAMS in corrosive environments, we conducted a long-term filtration test over 60 min in an acidic/alkaline environment simulated by acetic acid/ammonia. After prolonged filtration in these environments, the filtration efficiencies of SAMS−3mm (93.98% in acidic, 94.41% in alkaline) and SAMS−1mm (78.51% in acidic, 73.42% in alkaline) were significantly higher than those of N95 filter cotton (22.10% in acidic, 54.53% in alkaline) and N95 mask (18.18% in acidic, 16.32% in alkaline), as illustrated in Figure 5f. Similarly, SAMS−3mm and SAMS−1mm also maintained excellent filtration performance for PM2.5 (Figure S34). Optical photographs taken after the filtration test revealed that the reverse side of the N95 filter cotton and the N95 mask was penetrated by smoke particles, while no penetration was observed on the reverse side of SAMS−3mm and SAMS−1mm (Figures S35 and S36). These results fully demonstrate the stability and durability of the SAMS filter in a corrosive environment.

4. Conclusions

We have successfully developed a customizable, flexible, superamphiphobic, and reusable silica composite aerogel. Theoretical and experimental results demonstrate that its high porosity (~95%) and three-dimensional structure provide ample airflow passages, minimizing the trade-off between pressure drop and filtration efficiency. Furthermore, nano-sized pores further enhance filtration performance. These attributes enable the aerogel to maintain high PM0.3 filtration efficiency (~98.52%) even after 50 cycles in a traditional artificial simulation environment, highlighting its sustainability and cost-effectiveness. Moreover, the aerogel exhibits robust performance in complex environments, including high humidity (water mist), high temperature (50–250 °C), and corrosive solutions or atmospheres, demonstrating its reliability and broad applicability. Air purifiers utilizing this silica composite aerogel have shown excellent filtration performance in real-world applications, validating its potential for broader use.