# Nanomaterials in Photocatalysis: An In-Depth Analysis of Their Role in Enhancing Indoor Air Quality
## 12 Applications  
Photocatalytic nanomaterials are actively finding roles in practical applications for VOC removal, especially in air purification systems that target pollutants in both indoor and outdoor environments. Titanium dioxide (TiO\({}_{2}\)) is widely applied in consumer-grade air purifiers, HVAC systems, and surface coatings due to its ability to break down VOCs like formaldehyde, benzene, and toluene under light exposure. TiO\({}_{2}\)-coated surfaces are increasingly used in hospitals, schools, and public spaces to maintain clean air quality, as these coatings can continuously degrade airborne VOCs in the presence of light. Advances in TiO\({}_{2}\) modification, including doping with metals or integrating with visible-light-responsive semiconductors, have expanded its use indoors where natural light is limited. This has led to the commercialization of visible-light active TiO\({}_{2}\) products, such as wall and ceiling panels, that actively reduce VOC concentrations in residential and office spaces, directly addressing air quality issues without requiring complex machinery.  
Carbon-based materials, such as graphene and carbon nanotubes (CNTs), are used to enhance the performance of air purification devices and VOC capture systems. These materials, when combined with other photocatalysts, improve charge separation and increase the surface area available for VOC adsorption and degradation. Carbon-TiO\({}_{2}\) composites are now featured in advanced air purifier filters, providing a dual-function system that captures VOCs effectively while degrading them through photocatalysis. Graphene-based photocatalytic filters are also gaining traction in HVAC systems for commercial buildings, airports, and malls, where large volumes of air need to be processed continuously. This application is especially valuable for reducing indoor pollution levels in high-traffic areas where VOC levels can accumulate due to limited ventilation. Additionally, CdS-based composites, while less common due to stability issues, have found niche applications in industrial VOC treatment, such as air scrubbers for chemical processing plants where CdS's visible-light activation can be efficiently used under controlled conditions.  
More advanced materials like metal-organic frameworks (MOFs), perovskites, and transition metal dichalcogenides (TMDs) are pushing the boundaries of photocatalytic air purification technology. MOFs, with their high porosity and tunability, are being developed into filters and adsorbents tailored for high-performance VOC removal, especially in environments with sensitive air quality requirements like museums, archives, or pharmaceutical facilities. MOF-coated air filters can target specific VOCs based on the framework's design, offering highly selective purification for applications where traditional filters may fall short. Perovskites, known for their excellent light absorption, are being tested in photocatalytic coatings for outdoor building facades and public infrastructure to combat urban pollution by degrading VOCs emitted from traffic and industry. Although their practical application is still limited due to stability challenges, perovskite-based photocatalysts could soon contribute significantly to air quality management in urban areas. TMDs, such as MoS\({}_{2}\), are also being explored for industrial VOC treatment applications, where their strong visible-light absorption can be applied in large-scale photoreactors for factories or waste treatment facilities. By leveraging their high catalytic efficiency, TMD-based systems offer promising solutions for settings with high VOC emissions, providing cleaner air through enhanced photocatalytic degradation.