where O 1 /O 2 are the oxygens in H 2 O 2 , shown in Figure . The index i is associated with different TS configurations within each pocket, starting from the structure where H 2 O 2 is the most parallel to the oxo group (σ 1 ) and then moving clockwise along the NbO 1 axis. The values of σ i are reported in Table of the SI. Note that this parameter is useful for keeping track of various configurations within a pocket, but it is not one of the defining parameters for a bare site. Ideally, only the latter should be sufficient to distinguish sites with "high" or "low" activity.