Molecular Building Block-Based Electronic Charges for High-Throughput Screening of Metal–Organic Frameworks for Adsorption Applications

Metal–organic
frameworks (MOFs) are porous crystalline materials
with attractive properties for gas separation and storage. Their remarkable
tunability makes it possible to create millions of MOF variations
but creates the need for fast material screening to identify promising
structures. Computational high-throughput screening (HTS) is a possible
solution, but its usefulness is tied to accurate predictions of MOF
adsorption properties. Accurate adsorption simulations often require
an accurate description of electrostatic interactions, which depend
on the electronic charges of the MOF atoms. HTS-compatible methods
to assign charges to MOF atoms need to accurately reproduce electrostatic
potentials (ESPs) and be computationally affordable, but current methods
present an unsatisfactory trade-off between computational cost and
accuracy. We illustrate a method to assign charges to MOF atoms based
on ab initio calculations on MOF molecular building blocks. A library
of building blocks with built-in charges is thus created and used
by an automated MOF construction code to create hundreds of MOFs with
charges “inherited” from the constituent building blocks.
The molecular building block-based (MBBB) charges are similar to REPEAT
chargeswhich are charges that reproduce ESPs obtained from
ab initio calculations on crystallographic unit cells of nanoporous
crystalsand thus similar predictions of adsorption loadings,
heats of adsorption, and Henry’s constants are obtained with
either method. The presented results indicate that the MBBB method
to assign charges to MOF atoms is suitable for use in computational
high-throughput screening of MOFs for applications that involve adsorption
of molecules such as carbon dioxide.