Low-Loading f-MXene/Fluorosilicone Hybrid Highly Hydrophobic Coatings: Anti-Photoaging Mechanism and Application in Durable Protection of Stone and Brick Cultural Heritage

In the surface protection of stone and brick cultural heritage, a primary challenge is that traditional polymeric coatings are prone to photooxidative degradation under ultraviolet (UV) irradiation, and the resulting aged fragments readily block the substrate micropores, leading to a loss of “breathability”. To address the performance conflict among waterproofing, breathability, and weather resistance, this study prepared few-layer Ti3C2TX MXene using a minimally intensive layer delamination (MILD) method. The poor compatibility between MXene and the fluorosilicone (FPS) resin matrix was effectively resolved through covalent modification with a silane coupling agent (KH-550). Results demonstrate that at an ultralow loading (0.5 wt%), the functionalized f-MXene is uniformly dispersed within the resin. This structure not only spontaneously constructs a hierarchical rough architecture on the surface that imparts high hydrophobicity (water contact angle of 131.6°), but its internal “labyrinth effect” also effectively blocks corrosive media. Simultaneously, the intrinsic water vapor transmission rate of the substrate is effectively maintained (with a reduction of less than 3%), and no visually perceptible color difference is generated (∆E = 1.2). Mechanically, f-MXene relies on interfacial interactions to act as a “nano-skeleton” for stress transfer, thereby increasing the uniaxial compressive strength of fragile limestone by 32.4%. Optical and spectroscopic characterizations further elucidate its anti-aging mechanism: f-MXene not only provides broadband UV shielding but also exhibits highly efficient radical scavenging activity during long-term UV aging. After 400 h of aging, the concentrations of hydroxyl and superoxide anion radicals within the system are significantly reduced, blocking the photooxidative chain reaction from the source. This work develops a composite protective material system for stone cultural heritage that simultaneously integrates high moisture permeability, minimal visual intervention, and long-term antioxidant performance.