Split-Charge Equilibration Parameters for Generating Rapid Partial Atomic Charges in Metal–Organic Frameworks and Porous Polymer Networks for High-Throughput Screening

The split-charge equilibration (SQE) method was parametrized to reproduce the quantum mechanical, electrostatic potential (ESP) in an atomistically and topologically diverse training set of 559 metal–organic frameworks (MOFs) and 45 porous polymer networks (PPNs). The training set contained a total of 17 elements and 31 unique element–element bonds, 13 inorganic SBUs, 101 organic SBUs, and 30 functional groups. The split-charge equilibration MOF electrostatic-potential-optimized, or SQE-MEPO, method was validated against a set of 585 (520 MOFs and 65 PPNs) that were not part of the training set by comparing the derived ESP to the quantum mechanical ESP and comparing the computed CO₂ uptakes and heats of adsorption at both low (0.15 bar) and high pressures (10 bar). For this large validation set, the SQE-MEPO ESP deviated from the QM ESP by 30% less than other parametrized charge determination methods with a mean absolute deviation (MAD) of 6.47 mHartree compared to the next closest method with a MAD of 9.53 mHartree. When comparing the CO₂ uptakes and heats of adsorption calculated with SQE-MEPO charges compared to charges best fit to reproduce the QM ESP, SQE-MEPO was found to have a have Pearson and Spearman correlation coefficients of >0.95 at both low and high pressures. SQE-MEPO allows for rapid charges to be generated for MOFs that provides DFT quality electrostatic interactions when simulating adsorption properties that are ideal for high throughput screening.