Enabling Computational Design of ZIFs Using ReaxFF

Abstract

Classical force fields have been broadly used in studies of metal–organic framework crystals. However, processes involving bond breaking or forming are prohibited due to the nonreactive nature of the potentials. With emerging trends in the study of zeolitic imidazolate frameworks (ZIFs) that include glass formation, defect engineering, and chemical stability, enhanced computational methods are needed for efficient computational screening of ZIF materials. Here, we present simulations of three ZIF compounds using a ReaxFF reactive force field. By simulating the melt–quench process of ZIF-4, ReaxFF can reproduce the atomic structure, density, thermal properties, and pore morphology of the glass formed (a gZIF-4), showing remarkable agreement with experimental and first-principles molecular dynamics results. The predictive capability of ReaxFF is further exemplified in the melting of ZIF-62, where the balancing of electronic and steric effects of benzimidazolate yields a lower T m. On the basis of the electron-withdrawing effect of the −NO2 group, ReaxFF simulations predict that ZIF-77 has an even lower T m in terms of Zn–N interaction, but its low chemical stability makes it unsuitable as a glass former. Because of its low computational cost and transferability, ReaxFF will enable the computational design of ZIF materials by accounting for properties associated with disorder/defects.

Structural, electronic, and dielectric properties of a large random network model of amorphous zeolitic imidazolate frameworks and its analogues

“…Various experimental characterization techniques used for discerning the structure of melt‐quenched ZIF glasses include X‐ray diffraction, Raman and Brillouin spectroscopy, neutron diffraction and positron annihilation lifetime spectroscopy (PALS) . Computationally, molecular dynamic (MD) simulations and ab initio calculations have been used, along with force field based approaches . A comprehensive review on the structural design, properties and potential applications of amorphous MOF and coordination polymer systems has recently been provided …”

Bond switching is responsible for nanoductility in zeolitic imidazolate framework glasses

“…The ZIF glasses were simulated using a previously described method. 18,24,25 The method has been found to offer good agreement with experimental differential correlation functions and density data. 18,24,25 The fracture toughness of the ZIF glasses is estimated using the method of Brochard.…”

Molecular Dynamics and Machine Learning in Catalysts

“…The initial ReaxFF only described the hydrocarbons and gradually expanded to other materials, such as Si, SiO 2 [59], MgH [60], and Al 2 O 3 [61]. A tree-like development process [60,[62][63][64] was illustrated in the Figure 1. The formulation of ReaxFF is complicated, and until 2005, the form of expression became uniform and was supported direct access from some open-source software, such as LAMMPS [65] and PuReMD [66,67].…”