## 3 Experimental Approach
### \(\gamma\)-Graphyne
Without a particular substrate or template, the reaction conditions are simple to manage and inexpensive. Compared to previously discussed mechanical ball milling or ultrasonic-assisted synthesis methods, it could obtain \(\gamma\)-graphyne in high yield with minimum equipment requirements, successfully meeting mass production needs. Later, Pd nanoparticle clusters were decorated over the synthesized \(\gamma\)-graphyne sheets, which exhibit excellent catalytic activity towards the reduction of 4-nitrophenol (4-NP) because of the synergistic effect of Pd nanoparticles with the high surface area of \(\gamma\)-graphyne. In another work, using 1,3,5-tribromo-2,4,6-triethynylbenzene (TBTEB), Tetrakis (triphenylphosphine) palladium(0) [Pd(PdPh\({}_{3}\))\({}_{4}\)], and pyridine as the monomer, catalyst, and solvent, respectively, Desyatkin et al. [107] synthesised multilayer \(\gamma\)-graphyne through the Sonogashira coupling reaction. TBTEB broke down in heated pyridine without the need for catalysts, producing an amorphous carbonaceous substance. The TBTEB in hot pyridine was treated to a stoichiometric quantity of Pd(PdPh\({}_{3}\))\({}_{4}\) and a Cu foil, resulting in a black, glossy material with submicron-sized crystalline domains oriented randomly. Figure 10: Catalyzed coupling reaction route for \(\gamma\)-graphyne preparation using hexabromobenzene and acetylenedicarboxylic acid in a Pd-catalyzed one-pot reaction. Reproduced from reference [106]. Figure 9: Proposed reaction mechanism for the sonochemical synthesis of \(\gamma\)-graphyne, highlighting the acoustic cavitation-driven activation and enhanced molecular interaction. Reproduced with permission from reference [104] © 2020 Elsevier. Upon utilizing Pd(PdPh\({}_{3}\))\({}_{4}\) and copper iodide (CuI), the reaction produced hexagon-shaped flakes of \(\gamma\)-graphyne, indicating significantly increased crystallinity (as demonstrated in Figure 11). The \(\gamma\)-graphyne produced through the Sonogashira coupling reaction has better quality and purity in comparison to the mechanochemically synthesized \(\gamma\)-graphyne. Liu et al. [108] synthesized holey graphyne (HGY) from 1,3,5-tribromo-2,4,6-triethylbenzene as a monomer through a Castro-Stephens-type coupling reaction. For the synthesis of HGY, the interface technique between two immiscible liquids was employed. Copper acetate (CuOAc) and pyridine were present in the upper aqueous solvent layer. They served as a catalyst for the acetylenic homocoupling reaction, and the monomer was present in the lowest organic layer of dichloromethane (DCM). The reaction was then able to avoid the catalyst and monomer chance contact by adding a buffer layer of water in the middle portion, and the carbon-carbon coupling reaction at ambient temperature was conducted for 48 h in an inert argon environment for the synthesis of HGY. Additionally, alkyne metathesis is another method for the synthesis of \(\gamma\)-graphyne. Using this method, the synthesis of \(\gamma\)-graphyne was suggested employing 1,2,3,4,5,6-hexapropyylbenzene (HPB) as a monomer, but the first attempts failed due to the difficulties of the fabrication of an efficient catalyst [109]. Later, Hu et al. [110] created an efficient process via alkyne metathesis to produce highly crystalline bulk \(\gamma\)-graphyne. They were first trying to prepare \(\gamma\)-graphyne from HPB monomer only, and they obtained an amorphous solid with undesired side products. Then, 1,2,3,4,5,6-hexakis [2-(4-hexylphenyl) ethynylbenzene (HHEB) was used as a comonomer with HPB, and they were very successful in the synthesis of highly crystalline \(\gamma\)-graphyne. According to them, HHEB significantly improved the solubility of \(\gamma\)-graphyne oligomers, allowing them to develop into larger ordered domains prior to precipitation, leading to highly crystalline material [110; 111]. Until now, few methods have been developed for synthesizing \(\gamma\)-graphyne, and the developed methods have some limitations, such as complex methods, expense, time consumption, low yield, etc.