Zeolite Loaded-C3N4 Composite as an Intelligent Self-Cleaning Material for Simultaneous Enhanced Formaldehyde Removal and Concrete Reinforcement

The integration of indoor air purification and structural enhancement in cementitious materials remains a significant challenge. Formaldehyde, a predominant volatile organic compound in indoor environments, poses substantial health risks, while the inherent brittleness of cement-based materials adversely affects their structural integrity and long-term performance. Conventional solutions often address these issues separately, resulting in a lack of multifunctionality. Herein, we report a zeolite-loaded graphitic carbon nitride (g-C3N4) composite (ZSM-5/g-C3N4) that simultaneously enhances the mechanical properties of cement and degrades indoor formaldehyde under visible light. The composite was synthesized via an in situ growth strategy, enabling uniform loading of g-C3N4 onto the zeolite framework to create a synergistic interface for dual functionality. Structural characterization, including X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller, and ultraviolet-visible diffuse reflectance spectroscopy, was performed to confirm the successful formation and physical-chemical properties of ZSM-5/g-C3N4. The photocatalytic activity for gaseous formaldehyde degradation along with compressive strength and workability were evaluated. At a dosage of 0.9 wt% in cement, the composite enhanced compressive strength by 24.4% after 28 days of hydration, which is attributed to its role as a nanofiller and hydration accelerator. Concurrently, the modified cement exhibited exceptional formaldehyde removal efficiency, achieving a 69.9% degradation rate of gaseous formaldehyde (∼1.0 mg/m3) within 18 h under visible light (λ>420 nm), owing to the outstanding photocatalytic activity of the ZSM-5/g-C3N4. However, further investigations are needed regarding long-term durability (e.g., sulfate resistance, carbonation resistance) and the scalability of the synthesis process. This work pioneers a multifunctional cement additive strategy that simultaneously addresses indoor air purification and structural serviceability through sustainable material design.