Luminescent and Conductive Hybrid Materials based on Nanoscale Metal-Organic Frameworks and (Bio)Polymers

Abstract

This PhD thesis is centred around a unifying theme: the design and fabrication of hybrid materials that integrate nanoscale metal-organic frameworks (nanoMOFs) with (bio)polymers, targeting advancements in materials science and greener chemistry. A multi-faceted research approach has been applied to address this topic, with three main objectives: first, to synthesise nanoscale versions of bulk MOFs known from the literature; second, to develop nanoMOF@polymer hybrid materials with multi-level anti-counterfeiting mechanisms; and third, to synthesise environmentally friendly nanoMOF@biopolymer materials according to green chemistry principles. During the elaboration of the set scientific scope, all key objectives were successfully achieved, leading to notable achievements in the areas studied. A surfactant-assisted bottom-up synthesis route has successfully produced nanoMOFs with enhanced photophysical and morphological properties compared to their bulk versions. Mixed-matrix-membranes (MMMs) and powders composed of lanthanide-containing nanoMOFs (nLn³⁺-MOFs) and anthropogenic polymers (APs) have been developed, exhibiting multi-level anti-counterfeiting with interconnected properties, making them highly secure and difficult to replicate, thereby suitable for security-related applications. Aiming towards sustainability, developed nLn³⁺-MOFs were combined successfully with biopolymers yielding biodegradable and recyclable MMMs, hydrogels and cryogels. These bio-based materials demonstrating high regeneration capacity and stability over multiple recycling steps, align with green chemistry principles. Dispersibility and particle distribution benefit from the nanocharacter of nLn³⁺-MOF particles, which is a critical requirement for stable and resilient hybrid materials. The visible (Vis= Eu³⁺, Tb³⁺) and invisible (NIR= Yb³⁺) photoluminescence of developed nLn³⁺-BDC (BD^C2−= benzene-1,4-dicarboxylate), together with the conductivity of the APs polystyrene sulfonate (PSS) and pyrolysed resorcinol-formaldehyde (pRF) were used to create an additive multi-level anti-counterfeiting. Each feature (Vis-light, NIRlight, conductivity) represents a certain level of security, while they are interconnected by optical and physical properties – changing one will inevitably change another of the levels. The materials developed are designed to be difficult to replicate for unambiguous marking of valuable goods. As materials science has to address sustainability to overcome environmentally relevant challenges in the future, APs have been replaced by biodegradable nature-based biopolymers agar and gelatine. Luminescent MMMs made from nEu³⁺-BDC@biopolymers have been successfully recycled ten-times, while the red luminescence allows for the monitoring of the material’s condition. Resilient nEu³⁺-BDC in boiling water and freezing temperatures as well as water-based synthesis routes, render these materials suitable alternatives for AP-based hybrid materials. Altogether: improved synthesis techniques, application-driven approaches and biodegradable alternatives enable the creation of advanced nanoMOF@(bio)polymer hybrid materials supporting anti-counterfeiting, sustainability and circular economy.