Theoretical Insights into the Tuning of Metal Binding Sites of Paddlewheels in rht‐Metal–Organic Frameworks

Abstract

Theoretical investigations of CO2 sorption are performed in four members of the highly tunable rht-metal-organic framework (MOF) platform. rht-MOFs contain two Cu(2+) ions that comprise the metal paddlewheels and both are in chemically distinct environments. Indeed, one type of Cu(2+) ion faces toward the center of the linker whereas the other type faces away from the center of the linker. Electronic structure calculations on the series of rht-MOFs demonstrate that one of the Cu(2+) ions has a consistently higher charge magnitude relative to the other. As a consequence, the Cu(2+) ion with the higher partial positive charge acts as the favored sorbate binding site at initial loading as revealed by grand canonical Monte Carlo (GCMC) simulations that include many-body polarization. It was found that the charge distribution about the copper paddlewheels is dependent on the type of functional groups present on the linker. This study demonstrates how the binding site about the metal paddlewheels in the rht-MOF platform can be controlled by changing the functionality on the organic ligand.

Polarizable Force Field for CO2 in M-MOF-74 Derived from Quantum Mechanics

“…Furthermore, substantial work concerning polarizable force fields for MOFs with open metal sites has been carried out by the group of Space et al Initially, the group focused on adsorption of H 2 in MOFs with open metal sites. 19−21,25,28 Recently, these authors also developed force fields for CO 2 30,50,51 and even small hydrocarbons. 51 To consider polarization, the induced dipole method was applied.…”

“…More simulation details can be found in our previous studies 27,32 and the work of Lachet et al 31 Here, LJ force field parameters of nonmetal atoms for M-MOF-74 are assigned according to the UFF force field, 55 a generic force field frequently used for the modeling of MOFs. 21,25,30,48 For CO 2 , the TraPPE force field is applied which is commonly used to describe CO 2 adsorbed in MOFs. 56 The TraPPE force field describes the vapor–liquid equilibrium of CO 2 well.…”

“…29 Besides, the improved understanding and design of the electrostatic environment could be beneficial to better customize MOFs for certain applications. 30 Unfortunately, excessive computational costs do still prevent polarizable force fields from being widely applied in Monte Carlo simulations. 27 In our previous work, we verified the potential of polarizable force field for CO 2 in M-MOF-74 by adjusting the force field to reproduce experimental measurements.…”

MPMC and MCMD: Free High‐Performance Simulation Software for Atomistic Systems

“…Our aim with MPMC and MCMD is to leverage the best hardware available to date, increase the physical accuracy of traditional force field modeling through the inclusion of explicit, long‐range many‐body polarization in both the energetics and forces. We have used both codes in many published theoretical studies but have not formally introduced them until now.…”

Potential of polarizable force fields for predicting the separation performance of small hydrocarbons in M-MOF-74

“…Unfortunately, the simulations which considered explicit polarization took at least 2 to 10 times longer than standard Monte Carlo simulations. Moreover, the group of Space et al applied the induced dipole method to describe adsorption in MOFs with open metal sites 41,42,52,53,[64][65][66][67] . The early work of these authors focused on the adsorption of H 2 in MOFs with open metal sites 42,52,53,64,65 .…”