Atomic anchoring and friction-induced graphitization in nitrilotriacetate esters for customizable lubrication

The rational design of lubricants that exploit robust interfacial adsorption and friction-induced tribofilm formation is crucial for achieving tailored performance. Conventional ester lubricants often suffer from weak adsorption and the formation of inferior metal soap films. Herein, we report a molecular engineering strategy to synthesize a series of nitrilotriacetate esters with customizable structures by regulating alkyl chain length, branching, and ester group count. The optimized tridecyl 2,2′,2″-nitrilotriacetate (TDNA) exhibits superlative lubrication performance. Its trigonal pyramidal geometry, featuring three ester groups coordinated with a central nitrogen atom, facilitates a stable five-membered chelate structure that acts as a powerful “atomic anchor” to the metal surface, ensuring strong interfacial adhesion. The three linear alkyl chains further self-assemble via intensive van der Waals interactions, forming a dense and highly ordered molecular film. Under rubbing incitation, this robust adsorbed layer acts as a sacrificial precursor, undergoing in-situ degradation and metal-catalyzed reorganization into a protective graphene-like carbon tribofilm, rather than conventional metal soaps. This synergistic mechanism of atomic anchoring and controllable graphitization establishes a self-renewing lubrication system, resulting in significantly reduced friction and wear. This work provides profound insights into the molecular-level design of high-performance, sustainable lubricants.