Architectural Design of Cu-MOF Based and its Derived Bimetal- Based Nanocomposites for Sensing of Toxic Chemicals and Harmful Gases

Abstract

Metal-organic framework (MOF) structures are crucial in numerous fields of materials science owing to their high tunability, formed by combining different metal and organic moieties, which can be utilized for different applications. Specifically, Cu-MOFs are promising materials for gas and electrochemical sensing applications due to their unique combination of high surface area, tunable structure, redox properties, and catalytic activity. These features make them ideal candidates for use in sensors for environmental monitoring. The sensing activity as well as the stability of these materials, can be enhanced by decorating with bimetallic nanoparticles, modifying with reduced graphene oxides (rGO) supports. Additionally, another effective approach for enhancing these activities is to derive morphology and composition-tuned bimetal oxides. This consequently facilitates the development of innovative materials with encouraging properties. Keeping this in mind, the PhD thesis is focused on the architectural design of Cu-MOF-based and its derived bimetal-based nanocomposites for sensing toxic chemicals and harmful gases through the alteration in their shape, size, morphology, and the replacement of cations, achieved through various synthetic methods, leads to significant variations. Briefly, the thesis focused on two major parts. The first part includes the synthesis of Cu-based MOF and modifying it with bimetallic nanoparticles, forming its bimetallic MOF structure, deriving bimetal oxides, and finally forming composite with reduced graphene oxide for the potential electrochemical sensor of triclosan, atrazine, and clioquinol. The other part involves the synthesis of MOF-derived alloy and core-shell bimetal oxides with changes in the cation of the shell and morphology of the core for the gas-sensing application of toxic gases (NO2, CH4, and NH3). In the first project, I have demonstrated the synthesis of NiCo bimetallic nanoparticle decorated Cu-MOF modified rGO nanocomposite for electrochemical sensing of triclosan (Chapter 2, J. Electroanal. Chem. 2023, 943, 117589). After that, reducing complexity in synthesis, a one-step synthesis of CuNi- bimetallic MOF wrapped N-3DrGO was done for atrazine sensing. (Chapter 3, Manuscript Submitted). Lastly, to overcome the moisture instability and thermal stability by retaining the structure, morphology, and properties of MOF, in this chapter cation substituted Cu-based bimetallic MOF derived bimetallic oxides (CuO/NiO, CuO/ZnO, CuO/Mn2O3) modified 3DrGO nanocomposite was developed for the sensing of clioquinol. (Chapter 4, Manuscript to be submitted). The gas sensing part also includes three major chapters. In the first chapter of gas sensing, a comparison study was conducted between traditional and MOF-mediated synthesis of CuO/NiO bimetal alloy oxides decorated on rGO for NO2 sensing. (Chapter 5, ACS Appl. Electron. Mater. 2024, 6, 2349). Later, the efficiency of the core-shell structure with the varying metal ions of the shell (Zn, Ni, Co) modified with N-3DrGO was carried out for room temperature methane sensing. (Chapter 6, ACS Appl. Electron. Mater. 2025). Finally, after concluding the MOF-derived method with CuO@Co3O4 morphology showed the highest sensing performance, in the last chapter, interest was given to the synthesis of morphology varied core of CuO@Co3O4 oxides (cube, sphere, and octahedron) modified with N-3DrGO flexible sensor for room temperature ultralow level ammonia sensing. (Chapter 7, Manuscript to be Submitted). The materials discussed in this thesis have demonstrated exceptional sensitivity, selectivity, stability, efficiency, and recyclability, making them a valuable system for the aforementioned applications that hold considerable environmental importance.