To differentiate the activity of Zr clusters with missing-linker defects, O-vacancies, or both, we examined cluster-GO interactions for g 0 (pristine), g 1,1 (missing-linker), g 2,2 (Ovacancies), and g 4,2 (missing-linker + O-vacancies). In the calculated electrostatic potential maps (Figure ), we see stark changes in the charge distribution between the four distinct clusters. As expected, a large positively charged area around the Zr cus sites in g 2,2 and g 4,2