Transition states were optimized on ORCA in two steps. First, potential energy surface (PES) scans were computed where the presumed transition state mode, such as a bond length or bond angle, was incrementally changed and fixed while geometry optimizing all other degrees of freedom excluding the first and second coordination sphere atoms of the metals. The maxima from these PES scans were used as initial guesses for a partitioned rational-function optimization (P-RFO) 121 to locate the transition state structures (Supporting Information Text S2 and S3). Transition state identities were verified by performing frequency calculations to ensure that an imaginary frequency corresponding to the expected transition state mode was observed among other small imaginary frequencies associated with the imposed constraints. literature; computational details on transition state searching; job rescue using spin projection on free energy landscape structures; spin projection results on Mn MOF reaction coordinates at B3LYP-D3/LACVP*; spin projection results on Mn MOF reaction coordinates at B3LYP-D3/def2-TZVPP; raw free energy landscapes with N2O; IRC path for oxo formation using N2O on DADLEC; IRC path for oxo formation using N2O on LUSHOX04; free energy landscape of EBUREA with N2O; IRC path for oxo formation using N2O on EBUREA; free energy landscapes of DADLEC, EBUREA and LUSHOX04 with O2; IRC path for oxo formation using O2 with CO co-reductant on DADLEC; IRC path for superoxo and CO complexation on LUSHOX04; IRC path for O-O cleavage from superoxo-CO complex on EBUREA; representative IRC path for HAT on LUSHOX04; energetic span analysis; discussion on preparing SBU cluster models for DFT; custom modifications made to SBU clusters after MOFSimplify SBU extraction; comparison of linker-like anions of different sizes for SBU capping; SBU capping methods; basis-set sensitivity of DE(oxo), DE(HAT), and DE(release); computational details on job rescue; metal-oxo bond length scans in representative doublet monocupric oxo intermediates; discussion on generation of intermediates; illustration of intermediate generation; DFT job statistics on SBUs (PDF)