Efficient synthesis of alkynyl carbon materials derived from CaC2 through solvent-free mechanochemical strategy for supercapacitors

The 12-Ethynylmonocarba-closo-dodecaborate Anion: A Ligand for Metal Alkynide Complexes (M = Li, Na, Ca, Zn)

We report the first isolation of metal alkynide complexes (2a-d) incorporating lithium, sodium, calcium and zinc based on the monocarborane endo/exo-dianionic framework [CB11H11-12-C≡C]2-. These complexes are synthesized via the deprotonation of terminal alkynes and optimized using lithium, sodium, calcium, and zinc hexamethyldisilazide bases to achieve enhanced yields and crystal stability. X-ray crystallography and NMR spectroscopy reveal unique coordination geometries, including a rare chair-shaped Li4C2O2 unit in 2a, multinuclear units in 2b-c, and a hexagonal Zn3C3 unit in 2d. Subsequent nucleophilic reactions with benzophenone afford propargylic alcohols (3) with high efficiency, demonstrating their utility in selective synthetic routes for complex molecular assembly. This work not only highlights the reactivity of alkali and alkaline-earth metals in monocarborane metal acetylides but also offers valuable insights into their structural characteristics and potential applications in advanced materials and catalytic systems.

Calcium Carbide (CaC2) as a C2-Synthon by Mechanochemistry

Mechanochemical reactions by ball milling have opened new avenues in chemical synthesis. Particularly, mechanochemistry has facilitated the reaction of insoluble materials to simplify stablished synthetic protocols and develop new ones. One notable application involves the use of calcium carbide (CaC2) as a C2-synthon through mechanochemistry, which has offered a more practical alternative to incorporate C2-units compared to the conventional use of highly flammable gaseous acetylene. For example, by ball milling, the acetylenic anions [C2]2- found in CaC2 have been harnessed for the synthesis of diverse functional carbon materials as well as discrete organic molecules. This Concept aims to contribute to the conceptualization of this innovative approach while highlighting both its advantages and the challenges inherent in the use of CaC2.

Construction of Nitrogen-abundant Graphyne Scaffolds via Mechanochemistry-Promoted Cross-Linking of Aromatic Nitriles with Carbide Toward Enhanced Energy Storage

The 2D graphyne-related scaffolds linked by carbon-carbon triple bonds have demonstrated promising applications in the field of catalysis and energy storage due to their unique features including high conductivity, permanent porosity, and electron-rich properties. However, the construction of related scaffolds is still mainly limited to the cross-linking of CaC₂ with multiple substituted aromatic halogens and there is still a lack of efficient methodology capable of introducing high-concentration heteroatoms within the architectures. The development of alternative and facile synthesis procedures to afford nitrogen-abundant graphyne materials is highly desirable yet challenging in the field of energy storage, particularly via the facile mechanochemical procedure under neat and ambient conditions. Herein, graphyne materials with abundant nitrogen-containing species (nitrogen content of 6.9-29.3 wt.%), tunable surface areas (43-865 m²  g^-1 ), and hierarchical porosity are produced via the mechanochemistry-driven pathway by deploying highly electron-deficient multiple substituted aromatic nitriles as the precursors, which can undergo cross-linking reaction with CaC₂ to afford the desired nitrogen-doped graphyne scaffolds efficiently. Unique structural features of the as-synthesized materials contributed to promising performance in supercapacitor-related applications, delivering high capacitance of 254.5 F g^-1 at 5 mV s^-1 , attractive rate performance, and good long-term stability.

Thermal Mapping of Self-Promoted Calcium Carbide Reactions for Performing Energy-Economic Processes

The syntheses of various chemical compounds require heating. The intrinsic release of heat in exothermic processes is a valuable heat source that is not effectively used in many reactions. In this work, we assessed the released heat during the hydrolysis of an energy-rich compound, calcium carbide, and explored the possibility of its usage. Temperature profiles of carbide hydrolysis were recorded, and it was found that the heat release depended on the cosolvent and water/solvent ratio. Thus, the release of heat can be controlled and adjusted. To monitor the released heat, a special tube-in-tube reactor was assembled using joining part 3D-printed with nylon. The thermal effect of the reaction was estimated using a thermoimaging IR monitor. It was found that the kinetics of heat release are different when using mixtures of water with different solvents, and the maximum achievable temperature depends on the type of solvent and the amount of water and carbide. The possibility of using the heat released during carbide hydrolysis to initiate a chemical reaction was tested using a hydrothiolation reaction—the nucleophilic addition of thiols to acetylene. In a model experiment, the yield of the desired product with the use of heat from carbide hydrolysis was 89%, compared to 30% in this intrinsic heating, which was neglected.