To address the CO adsorption puzzle, many refined semilocal generalized gradient approximation (GGA) (like RPBE and BEEF used in this study) or meta-GGA functionals have been proposed. While these can accurately predict adsorption energy at the top site, they often fail to differentiate adequately between hollow and bridge sites, unlike methods that correctly identify the top site as energetically preferred. Other approaches, such as DFT+U , DFT+U densities for meta-GGA , and hybrid functionals , have been explored to improve the description of both adsorption energy and site preference. Additionally, higher-level methods like RPA and embedding approaches have successfully addressed this issue by providing more accurate electron correlation treatments beyond GGA functionals. These studies underscore the need for more accurate electron correlation treatments, such as direct exchange-correlation methods beyond GGA, to effectively address the CO* adsorption site problem.