Development of coordination polymer and/or nanocrystal based smart materials as sensor and micropollutant removal agent

Abstract

The increasing presence of organic micropollutants in water systems poses a critical threat to environmental and human health due to their persistence, toxicity, and potential for bioaccumulation. Simultaneously, the growing demand for sensitive, selective, and cost-effective sensing platforms in environmental monitoring and biomedical applications has driven the search for multifunctional materials that can address both detection and remediation challenges. Coordination polymers, quantum dots, and metal–organic frameworks (MOFs) have emerged as promising candidates owing to their tunable optical properties, high surface area, and versatile structural designs. Through precise control of composition, morphology, and surface chemistry, these materials can be engineered to exhibit tailored photophysical responses while maintaining strong adsorption capacities toward target contaminants. Recent advances have demonstrated that heteroatom doping, solid-state embedding, and macrocyclic functionalization can significantly enhance both sensing performance and pollutant removal efficiency. The pursuit of advanced functional materials capable of addressing both environmental and sensing challenges has driven extensive research into coordination polymers, quantum dots, and hybrid nanostructures. These materials offer unique opportunities for integrating high surface area, tunable porosity, and customizable optical properties into multifunctional platforms. This thesis focuses on the rational design, synthesis, and application of coordination polymer and nanocrystal-based systems with dual capabilities in selective sensing and efficient micropollutant removal. By employing targeted doping strategies, solid-state embedding, and macrocyclic surface modification, the optical responses and adsorption efficiencies of these materials were systematically optimized. The work encompasses the development of doped carbon dots for wavelength-selective biosensing, indium-based quantum dots with thermo-responsive fluorescence for thermal sensing and water decontamination, and macrocycle-modified metal–organic frameworks with enhanced pollutant adsorption. Collectively, these efforts demonstrate a coherent approach to engineering environmentally sustainable smart materials that bridge the gap between advanced sensor technologies and practical remediation solutions. The aim of this thesis is to develop coordination polymer and/or nanocrystal-based smart materials that can serve as high-performance, environmentally sustainable platforms for both sensor applications and the removal of organic micropollutants. Three research articles have been published in connection with this doctoral study, and each work is presented in a separate chapter. The first study is mentioned in chapter 2 the synthesis of nitrogen- and boron-doped carbon dots (CDs) via a microwave-assisted method for selective metal ion and ATP xxiv detection. Structural analysis confirmed distinct surface functionalities for each dopant type, influencing photophysical behavior through surface- and core-state interactions. Optical studies revealed excitation-dependent emissions, with Cu²⁺ inducing strong fluorescence quenching at shorter wavelengths (300 nm) due to surface-state effects, and Ag⁺ causing quenching at longer wavelengths (450 nm) via core-state mechanisms. Boron-doped CDs exhibited up to 20-fold fluorescence enhancement in the presence of Mg²⁺, Zn²⁺, and Cd²⁺, attributed to surface passivation. The strong affinity between Cu²⁺ and ATP enabled a label-free sensing platform using absorption and fluorescence spectroscopy. These results demonstrate that excitation wavelength control can modulate sensor selectivity, highlighting doped CDs as cost-effective, eco-friendly platforms with tunable optical responses for environmental and biological sensing applications. The second study mentioned in chapter 3 presents a one-pot synthesis of In₂S₃, ZnIn₂S₄, and Cu:ZnIn₂S₄ quantum dots embedded in oleic acid-based solid-state matrices, producing insoluble, thermally stable nanomaterials with bright orange fluorescence and quantum yields up to 31%. The solid-state format ensured uniform dispersion, solvent resistance, and stability up to 160 °C. ZnIn₂S₄ quantum dots exhibited reversible thermo-responsive fluorescence, while all materials showed high removal efficiency for cationic dyes, with In₂S₃ also effective against anionic dyes. These results demonstrate the potential of solid-state indium-based QDs for multifunctional applications in thermal sensing and water purification. The third study mentioned in chapter 4 the synthesis of fluorescent zeolitic imidazolate framework-8 (ZIF-8) nanocrystals functionalized with bis-carboxylate calix[4]pyrrole (BCCP), enabling both emission tunability and size control. Increasing BCCP concentration reduced particle size from ~270 nm to ~65 nm and altered crystallographic growth, while transforming the porosity from microporous to mesoporous behavior. The modified ZIF-8 exhibited bright whitish-blue fluorescence with a quantum yield of ~7.3% and enhanced micropollutant adsorption performance, attributed to synergistic effects of reduced size, altered porosity, and surface functionalization. These results demonstrate a versatile approach for integrating optical activity into MOF structures for sensing and environmental remediation applications.