@article{discovery10194590,
         journal = {Inorganic Chemistry},
          number = {17},
           title = {Chemical Conversions within the Mo-Ga-C System: Layered Solids with Variable Ga Content},
            year = {2024},
           pages = {7725--7734},
            note = {This version is the author-accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.},
       publisher = {RSC},
           month = {April},
          volume = {63},
            issn = {2052-1553},
             url = {https://doi.org/10.1021/acs.inorgchem.4c00107},
        abstract = {Layered carbides are fascinating compounds due to their enormous structural and chemical diversity, as well as their potential to possess useful and tunable functional properties. Their preparation, however, is challenging and forces synthesis scientists to develop creative and innovative strategies to access high-quality materials. One unique compound among carbides is Mo{$_2$}Ga{$_2$}C. Its structure is related to the large and steadily growing family of 211 MAX phases that crystallize in a hexagonal structure (space group P6{$_3$}/mmc) with alternating layers of edge-sharing M{$_6$}X octahedra and layers of the A-element. Mo{$_2$}Ga{$_2$}C also crystallizes in the same space group, with the difference that the A-element layer is occupied by two A-elements, here Ga, that sit right on top of each other (hence named "221" compound). Here, we propose that the Ga content in this compound is variable between 2:2, 2:1, and 2: {$\leq$}1 (and 2:0) Mo/Ga ratios. We demonstrate that one Ga layer can be selectively removed from Mo{$_2$}Ga{$_2$}C without jeopardizing the hexagonal P6{$_3$}/mmc structure. This is realized by chemical treatment of the 221 phase Mo{$_2$}Ga{$_2$}C with a Lewis acid, leading to the "conventional" 211 MAX phase Mo{$_2$}GaC. Upon further reaction with CuCl{$_2$}, more Ga is removed and replaced with Cu (instead of fully exfoliating into the Ga-free Mo{$_2$}CTx MXene), leading to Mo{$_2$}Ga{$_1$}{$_-$}?Cu?C still crystallizing with space group P6{$_3$}/mmc, however, with a significantly larger c-lattice parameter. Furthermore, 211 Mo{$_2$}GaC can be reacted with Ga to recover the initial 221 Mo{$_2$}Ga{$_2$}C. All three reaction pathways have not been reported previously and are supported by powder X-ray diffraction (PXRD), electron microscopy, X-ray spectroscopy, and density functional theory (DFT) calculations.},
          author = {B{\"u}chner, Carina and Kubitza, Niels and Malik, Ali M and Jamboretz, John and Riaz, Aysha A and Zhu, Yujiang and Schlueter, Christoph and McCartney, Martha R and Smith, David J and Regoutz, Anna and Rohrer, Jochen and Birkel, Christina S}
}