Abstract
Paper artifacts are irreplaceable carriers of human history and culture, yet they are inherently vulnerable to degradation through acidification, hydrolysis, and oxidation. Conventional conservation approaches, such as immersion and spraying, introduce liquid media and additives that can disturb fiber microstructure and alter appearance. Here we report a dry, depth‐programable vapor‐phase molecular infiltration strategy for paper‐based cultural heritage conservation. Using diethylzinc as a precursor, we achieve either surface‐confined or depth‐controlled zinc incorporation within cellulose fibers by tuning exposure kinetics, yielding zinc‐modified Xuan paper (Zn‐X). At the molecular level, zinc coordinates with oxygen‐containing functional groups in cellulose, forming Zn–O–cellulose linkages that reinforce the cellulose network. This atomic‐scale modification, in synergy with the hierarchical fiber structure, imparts deacidification, hydrophobicity, improved mechanical strength, and antibacterial activity, while also reducing flame spread with enhanced char formation and post‐burn legibility—all without compromising the original morphology and visual appearance. Furthermore, we demonstrate practical utility on a historical Qing‐dynasty manuscript, achieving increased hydrophobic protection with minimal color change and preserved text legibility. This work establishes a precise, minimally invasive, and multifunctional platform for the sustainable conservation of paper‐based cultural heritage.