Estimation of Framework Charges in Covalent Organic Frameworks Using Connectivity-Based Atom Contribution Method

In our previous work, an approach named connectivity-based atom contribution method (CBAC) was developed for estimating framework charges in metal-organic frameworks (MOFs). In this work, we extend the approach to covalent organic frameworks (COFs), another emerging family of nanoporous materials. The results show that those framework atoms with the same bonding connectivity (same atom type) in COFs have identical charges as that in MOFs; this further validates the suitability of the CBAC method and makes it possible to apply to other nanoporous materials. The CBAC charge databank previously established was extended to include 11 new atom types that are commonly involved in COFs, and excellent agreement was obtained between molecular simulations based on CBAC charges and those on quantum mechanically calculated charges.