loses the extra stabilization it had from the hydrogen bonding with the nearby hydroxy group, leading to even weaker adsorption of O2 (Supporting Information Figure ). In stark contrast, experimental measurements place the metal-O2 distance at 1.9 Å , aligning with the PBE results. The observed discrepancy between PBE+U CCSD(T) and the experiment can likely be attributed to two primary factors. Firstly, as previously mentioned, this system may be prone to significant static correlation errors, evidenced by the high T1 value of 0.0202, suggesting that CCSD(T) results may not be sufficiently reliable. Secondly, our current U CCSD(T) is fitted only to the SBU with an FM spin configuration. The potential energy curve of the FM spin configuration calculated using CCSD(T) exhibits a notably flat and repulsive energy curve, contrary to the experimental observations (Supporting Information Figure ). It is important to note that while our current U CCSD(T) value is fitted only to the SBU with an FM spin configuration, the optimal U CCSD(T) value varies based on the spin configuration. Consequently, the CCSD(T) result of the FM spin configuration is not likely to estimate the U value needed to calculate the adsorption energy for the Co2(OH)2-BBTA-O2 system with an AFM spin configuration. Systems with ambiguous spin coupling are therefore not good candidates for this calibration approach and rather require a comprehensive broken symmetry calculation to thoroughly understand their adsorption processes. Overall, the quality of the CCSD(T) evaluation on SBUs in comparison to experimental adsorption energies on the full MOF suggest some limitations for gas adsorption (Figure ).