Order–Disorder\nStructure in Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub>: Synthesis, Characterization,\nand Its Applications toward Photocatalytic Dye Degradation and Antibacterial\nActiviti

Design of Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub>, a metal carbon oxyfluoride [M–L–C–O–F]\ncomprising a p-block cation, was carried out by incorporating a carbon\natom inside the Sb<sub>4</sub> tetrahedral void of Ni<sub>3</sub>Sb<sub>4</sub>O<sub>6</sub>F<sub>6</sub>. Single crystals of Ni<sub>3</sub>Sb<sub>4</sub>O<sub>6</sub>F<sub>6</sub> and Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub> were grown by employing a hydrothermal\nsynthesis technique. Single-crystal X-ray diffraction (SCXRD) studies\nshow that the crystal structure of Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub> can be explained by both an ordered and a disordered\nstructure model with cubic symmetry (SG: <i>I</i>4̅<i>3m</i>). Disorder generates the four split carbon sites due\nto symmetrically identical positions at (−<i>x</i>, −<i>x</i>, <i>x</i>) with the occupancy\nof one quarter of each carbon site of their total occupancy. On the\nother hand, disorder can be avoided by fixing the carbon site at (0,\n0, 0), a special position with 100% occupancy at one site. Conversely,\nlowering of symmetry to tetragonal symmetry (SG: <i>I</i>4̅) provides comparatively low GOF and <i>R</i> values,\nwhich could also be a kind of structural modeling for Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub> considering the large data-to-parameter\nratio. Insertion of carbon introduces an indirect band gap energy\n(<i>E</i><sub>g</sub>), i.e., 1.75 eV, in Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub> compared to the direct\nband gap energy of its parent compound, Ni<sub>3</sub>Sb<sub>4</sub>O<sub>6</sub>F<sub>6</sub> (<i>E</i><sub>g</sub> = 3.25\neV), which was also confirmed from the theoretical study. Both Ni<sub>3</sub>Sb<sub>4</sub>O<sub>6</sub>F<sub>6</sub> and Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub> were explored as efficient\nphotocatalysts toward Methylene Blue dye degradation and excellent\nantibacterial agents against both Gram-positive and Gram-negative\nbacteria for the first time. The rate of dye degradation was greater\nfor Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub>, as evident\nfrom the kinetic study. The addition of 6% H<sub>2</sub>O<sub>2</sub> further increases the rate of dye degradation in both cases. The\nphotocatalysts were recycled up to seven consecutive cycles with 60\nand 80% minimum degradation efficiencies for Ni<sub>3</sub>Sb<sub>4</sub>O<sub>6</sub>F<sub>6</sub> and Ni<sub>3</sub>Sb<sub>4</sub>CO<sub>6</sub>F<sub>6</sub>, respectively. Radical scavenger test\nwas also performed to investigate the responsible reactive oxygen\nspecies (ROS) in this photocatalytic dye degradation reaction. The\nantibacterial study was carried out with eight distinct bacterial\nstrains, namely, <i>Staphylococcus</i> sp., <i>Salmonella</i> sp., <i>Pseudomonas</i> sp., Escherichia\ncoli, <i>Klebsiella</i> sp., <i>Bacillus</i> sp., <i>Enterobacter</i> sp., and <i>Proteus</i> sp<i>.</i> The bacterial disinfection properties of each\ncompound were monitored by examining the ability to suppress bacteria\nin liquid LB medium. The compounds were also characterized through\nenergy-dispersive X-ray (EDS), Fourier transform infrared spectroscopy\n(FTIR), powder X-ray diffraction (PXRD), field emission scanning electron\nmicroscopy (FE-SEM), and zeta potential study.