A review on functional group chemistry and structure-to-function design for mechanism-centric nanoparticle EOR

A significant challenge in advancing nanoparticle-based enhanced oil recovery (EOR) is the gap between synthesis and application. Many reviews catalog surface modification techniques but fail to explain why specific molecular features lead to success in EOR mechanisms. Our work addresses this gap by providing a mechanism-centric framework focused on structure-to-function relationships. This approach is vital because while nano-EOR promises to overcome the drawbacks of traditional recovery, the base nanoparticles themselves are often ineffective. Their low stability and poor interfacial performance in challenging reservoir environments necessitate surface functionalization. Instead of focusing on modification methods, we analyze how the deliberate addition of chemical groups like sulfonates, carboxylates, hydroxyls, amines, and alkyl chains directly impacts core EOR functions, including reducing interfacial tension (IFT), altering rock wettability, stabilizing emulsions and foams, and enhancing viscoelasticity. By elucidating the underlying molecular interactions (electrostatic, hydrogen bonding, hydrophobic), we build a clear pathway from chemical design to functional outcome. This review extends to advanced applications, including trigger-responsive smart nanoparticles and asphaltene inhibition. Ultimately, we provide a comparative analysis and a selection guide to empower researchers to rationally design nanoparticles for specific reservoir challenges, thereby accelerating the field's transition from empirical testing to predictive engineering.