Studies have shown that some MOFs with open metal sites, such as MOF-74-Mg (CPO-27-Mg, Mg2(dobdc)) 105 , show enhanced CO2 adsorption properties. 106-108 Therefore, we also examine the presence of open metal sites more broadly within the nodes of MOFs in USMOF DB beyond the privileged nodes we identified with high CO2:CH4 ratios (i.e., N38 and N61). While there are notable examples with open metal sites that prefer CO2, the presence of an open metal site alone is not the sole deciding factor in determining that MOFs will prefer CO2 over CH4. When considering only the most mechanically stable MOFs by requiring a bulk modulus (KVRH) greater than 10 GPa (i.e., rather than just 5 GPa), the set reduces to 340 MOFs. However, among these MOFs, MOFs with open metal sites do indeed show a strong preference for CO2 (Supporting Information Figure ). Thus, observation of the nodes with open metal site preference for CO2 cannot be fully decoupled from mechanical stability considerations, which removes less mechanically stable MOFs with large pore volumes that often exhibit high CH4 working capacities.