NanoMOF-Based Multilevel Anti-Counterfeiting by a Combination of Visible and Invisible Photoluminescence and Conductivity

This study presents nanosized metal-organic framwork (nanoMOF)-based multifunctional mixed-matrix-membranes (MMMs) and composite powders as extremely sensitive responder materials for a responder-stimulus based multilevel anti-counterfeiting. The physicochemical properties of nanoMOF-based composites offer a wide operational range as anti-counterfeiting tags. Nine responder materials are presented, constituted of trivalent lanthanide-containing nanoMOFs ([Ln<inf>3</inf>(bdc)<inf>4.5</inf>(H<inf>2</inf>O)<inf>3</inf>(dmf)<inf>2</inf>] (nLn-bdc); bdc²⁻═benzene-1,4-dicarboxylate; Ln═Eu, Tb, Yb) and polystyrene sulfonate, pyrolyzed resorcinol-formaldehyde and polysulfone as matrices. These materials inherit distinct properties, and their combination provides visible and near-infrared light emission and specific conductivity for multiple security level anti-counterfeiting. The additive and interdependent nature of security features in the developed anti-counterfeiting materials ensures that altering one feature will invariably affect others, thereby reinforcing the overall integrity and resilience of the security mechanism. Even the pitch-black composites of nLn-bdc and pyrolyzed resorcinol-formaldehyde show bright light emission to the near-infrared range, when stimulated by UV-light being suitable for black materials. This work also describes a matrix-based active contribution as security feature to an anti-counterfeiting tag, instead of being solely used as a carrier for the security feature-bearing nanoMOFs. The combination of multiple levels of security by different properties marks these multifunctional composites as anti-counterfeiting materials being complicated to copy including a proof-of-principle experiment.