İki boyutlu yariiletken pniktojenler (Bi, Sb ve BiSb): görünür/nir işik tetiklemeli fotoredoks C-H i̇şlevselleştirilmesinde yeni nesil fotokatalizörler

Two-dimensional (2D) nanomaterials, especially structures based on group 15 (pnictogen) elements (P, As, Sb, Bi), have become an important research topic in latest years due to their superior electronic, optical, tunable band gap and catalytic properties. However, the controlled and scalable synthesis of 2D heavy pnictogens such as Bi and Sb is very limited in the literature. The current studies have generally focused on single-element systems, and the effects of functionalization (covalent & non-covalent) and especially the formation of binary systems (e.g. BiSb) on the resulting materials have not been sufficiently investigated. Moreover, comprehensive studies systematically applying functionalization strategies such as covalent and non-covalent surface modification on such 2D heavy pnictogens and studying their catalysis in organic transformations are also lacking in the literature. On the other hand, photoredox C-H arylations under photoredox conditions have been played a significant role in modern organic synthesis as they allow the synthesis of complex molecules in an efficient, selective and green ways. They allow the direct activation of C-H bonds without the need for pre-activation steps and offer great advantages in a wide range of fields such as pharmaceuticals, materials and natural products synthesis. However, to catalyze such reactions efficiently, there is still a need for next generation photocatalytic materials with large surface area, suitable band structure and high chemical stability. The design and functionalization of 2D pnictogen semiconductors have the potential to create a powerful and innovative way for photoredox direct C-H activation processes. In this context, this thesis focuses on the controllable layered synthesis, covalent and non-covalent surface functionalization of 2D pnictogen nanostructures (Bi, Bi-B, Sb and BiSb) and systematic investigation of their photocatalytic performances in the photoredox C-H arylations of heteroarenes with diazonium salts under visible-light conditions. In the first part of the thesis, 3D layered Bi structures with an average lateral dimension of 300-500 nm were synthesized using a newly developed one-pot surfactant-assisted solvothermal synthesis method and subsequently 2D Bi nanostructures with about 3 atomic layers with a thickness of approximately 1.27 nm were obtained by separating it into layers with using the liquid phase exfoliation (LPE) method. The morphological, structural and electronic properties of the structures were investigated in detail by advanced characterization techniques such as Raman, TEM, SEM, AFM, XRD, XPS and Mott-Schottky. The optical band gap valence band of 2D Bi nanostructures was determined as 1.41 eV by XPS and Mott-Schottky analysis. Both covalent and non-covalent functionalization studies were carried out on the obtained 2D Bi nanostructures. It was determined that the material obtained with B after heteroatom doping within the scope of non-covalent functionalization increased the band gap from 1.41 eV to 1.51 eV compared to 2D Bi, while surface modifications significantly increased the stability and dispersion ability. The 2D Bi-B nanostructure was found to have approximately 5 atomic layers with a thickness of 2.635 nm by advanced technical analysis. Experiments carried out on a model photoredox direct C-H arylation reaction ( for each experiment, 0.25 mmol of furan and 0.25 mmol of 4-chlorobenzenediazonium salt are used, with optimization conditions applied throughout. ), 2D Bi provided 87% yield while B-doped 2D Bi exhibited 97% yield, and it was also demonstrated that the material can be effectively reused up to three times with a low amount of usage. In the second part of the thesis, 3D layered Sb structures with an average size of 200 nm were synthesized using a one-pot surfactant-assisted solvothermal synthesis method and 2D Sb nanostructures consisting of approximately 3 atomic layers with an average thickness of 1.06 nm were obtained by the LPE method. The optical band gap of 2D Sb nanostructures was determined as 0.96 eV by valence band XPS and Mott-Schottky analysis. In addition, the 2D Sb nanostructures were modified by both covalent and non-covalent functionalization. Furthermore, model photoredox direct C-H arylation reaction tests showed that the 2D Sb nanostructure showed a product with the yield of 90%. This reaction was carried out on a wide range of substrates, with yields ranging from 48% to 100%, demonstrating a broad application potential. Reusability tests showed that 2D Sb retains its structural and functional integrity for up to five cycles. In the third part of the study, which is the most exciting and unique in literature, the synthesis of 3D layered BiSb binary compound was carried out by a one-pot surfactant-assisted solvothermal synthesis method as in 3D layered Bi and Sb.The 3D layered BiSb that was obtained exhibited an average particle size of 50-70 nm. Furthermore, the LPE method was utilized to obtain few layered 2D BiSb nanostructures, which possessed approximately 3 atomic layers and an average thickness of 5.01 nm. Further technical analysis revealed that these structures have a smooth surface morphology and lateral size in the range of 20-50 nm. Analyses also showed that this binary structure with the composition Bi48Sb52 creates a novel synergistic effect compared to Bi or Sb monoelemental derivatives. In particular, the co-presence of Bi and Sb atoms resulted in a 1.32 eV band gap, providing a difference in the optical band gap compared to monoelemental structures, and thus the efficiency of the model photoredox in direct C-H arylation reactions increased up to 97%. In the wide range of substrates, high yields between 77% and 99% were achieved, thus demonstrating the material's broad application potential. Furthermore, the 2D BiSb nanostructure was found to exhibit high reusability and stability, maintaining its activity for up to five cycles. In summary, this thesis work fills important gaps in the literature by taking a holistic approach to the controlled synthesis of 2D pnictogen nanostructures by developed novel wet chemistry methods, covalent/non-covalent functionalization of the obtained 2D materials and synthesis of BiSb binary compound by wet chemistry method. This thesis makes an important contribution to the integration of pnictogen-based 2D nanostructures and functionalized binary compounds into photoredox catalysis applications. At the same time, we believe that the detailed characterization of all materials obtained in this thesis with advanced analytical techniques will be pioneering in terms of revealing the structure-catalytic performance relationship in detail and providing innovative contributions to the existing literature in the field. The obtained 2D Bi, Bi-B, Sb and BiSb nanostructures are promising for advanced catalytic applications and 2D materials engineering with their high photocatalytic performance, chemical stability and reusability. In the future, the potential use of these materials in different photoredox conversion reactions and catalytic processes can be investigated in detail in different fields.