While Figure and Figure show how the entire dataset changes with different density functionals, it is also important to investigate the degree of correlation between the various functionals. As shown in the parity plots in Figure , nearly every MOF has a larger predicted band gap with the HSE06 * (Figure ) and HSE06 (Figure ) functionals than with PBE. This is also the case for most of the closed-shell MOFs with the HLE17 functional, especially when 𝐸 g,PBE is above ~1.5 eV (Figure ). For the closed-shell frameworks (Figure ), there is a linear correlation between the computationally inexpensive PBE-quality band gaps and those calculated with the more accurate HSE06 * and HSE06 functionals as well as the HLE17 functional. As shown in Figure , a simple linear equation of the form 1.09𝐸 g,PBE + 1.04 eV can predict HSE06 band gaps with an 𝑅 2 value of 0.92, provided the frameworks are closed-shell systems and have HSE06 band gaps above ~1.0 eV. Similar linear equations can be obtained for HLE17 and HSE06 * for the closed-shell structures (Figure and Figure ). The correlation between PBE and the hybrid functionals is weaker for MOFs with open-shell character, hence the larger degree of scatter in the low 𝐸 g,PBE range of Figure and Figure . As might be anticipated based on trends in crystal-field splitting parameters and spin-pairing energies, most open-shell materials in the QMOF Database contain 3d transition metal cations (particularly Cu, Co, Mn, Ni, Fe, V, and Cr in decreasing frequency of occurrence) (Figure ). Previous theoretical work on transition metal complexes and gas-phase molecules containing transition metal cations has implicated large self-interaction errors (a consequence of each electron interacting with the total electron density, including its own ) as a major source of errors in systems with 3d transition metal cations that have open-shell character. More generally, self-interaction error is usually considered to be responsible for many of the deficiencies of DFT across virtually all properties and material classes, often due to the associated delocalization error. Since self-interaction error is partially decreased by the inclusion of HF exchange, this is a major reason that the hybrid functionals give different results than the local functionals for the band gap predictions in this work.