## 3 Computation Details  
All plane wave DFT calculations were performed using the projector augmented wave pseudopotentials [26] provided in the Vienna ab initio simulation package (VASP) [27]. The Perdew-Burke-Ernzerhof exchange-correlation with Hubbard U corrections [28; 29] were used with a plane wave expansion cutoff of 600 and 400 eV for the bulk and surface, respectively. We did not employ dispersion corrections because we found that the energetics of small molecules such CO and S were well predicted by DFT without D3 [30]. We believe that COS can be affected by the presence of dispersion corrections; however, the proposed COS absorption mechanism would not be changed with the dispersion interactions because the dispersion effects are canceled out when evaluating activation energy barriers [31; 32]. Various U values were tested to find a U value providing the proper lattice parameters of CuO. The tests showed that the U value of 8.5 eV provides proper lattice parameters of CuO, which agreed well with the experimental results. Based on the results, U of 8.5 eV was used for the computation. The C2/c space group was used with monoclinic crystal structure [33] to relax the bulk lattice constants until the forces reached at least 0.01 eV/A with the Monkhorst-Pack KPOINTS mesh, 8 \(\times\) 8 \(\times\) 8. The PBE+U relaxed bulk lattice constants of CuO (a = 4.754 A, b = 3.424 A, c = 5.178 A, \(\beta\) = 99.25\({}^{\circ}\)) were used to fix the lateral dimensions of the CuO(111) slab. These DFT-predicted CuO bulk lattice parameters agreed well with the experimental bulk lattice parameters (a = 4.682 A, b = 3.424 A, c = 5.127 A, \(\beta\) = 99.42\({}^{\circ}\)) [34]. Seventeen valence electrons were introduced including the 3p states in Cu for bulk and surface calculations because PBE failed to predict the experimental bulk lattice parameter without 3p electrons. This study focused on the CuO(111) surface, which is one of the three stable surfaces ((111), (\(\overline{1}\)11), and (011)) with a CuO crystal morphology [35]. The CuO(111) surface had a 3 \(\times\) 3 surface unit cell size with \(\sim\)9 A slab thickness. The surface consists of five layers with two fixed bottom layers. For the slab calculations, the interatomic force, 0.05 eV/A, and 2 \(\times\) 2 \(\times\) 1 KPOINTS mesh were used. A vacuum spacing of \(\sim\)20 A, which is sufficient to reduce the periodic interaction in the surface normal direction, was used. The pristine bare CuO(111) surface has two active sites of coordinatively unsaturated Cu (Cu\({}_{\text{cus}}\)) and saturated Cu sites (Cu\({}_{\text{sat}}\)) on the CuO(111) surface. The surface oxygen and subsurface oxygen were also labeled as O\({}_{\text{surf}}\) and O\({}_{\text{slab}}\), respectively. These sites are illustrated in Figure 5a. The effects of surface sulfur and surface oxygen vacancies on COS oxidation reaction toward CO\({}_{2}\) were also examined by introducing an O\({}_{\text{cus}}\) vacancy and a S surface to the CuO(111) surface. Figure 5b-d shows the described O vacancy and surface S atom-employed CuO(111) surfaces. All relaxed configurations of the adsorbed COS, CO, and CO\({}_{2}\) on the CuO(111) surface with S and oxygen vacancies are provided in this manuscript. Unless otherwise noted, the DFT calculations were performed for a single molecule adsorbed within the surface models described above. In this present study, we define the adsorption energy between a molecule and surface using Equation (2):  
\[E_{ads}=E_{slab}+E_{iso}-E_{slab+ads} \tag{2}\]  
where \(E_{slab}\), \(E_{iso}\), and \(E_{slab+ads}\) are the energy of a bare surface, isolated molecule, and a molecule adsorbed on the bare surface, respectively. In this adsorption energy, a larger positive energy indicates higher stability of the adsorbed molecule under consideration.