Herein, synthesizable candidate topologies to form zeolitic imidazolate frameworks (ZIFs) are efficiently identified from over 2 000 000 hypothetical structures in zeolite databases, using structural descriptors extracted from known ZIFs. A combination of intuition-based structural descriptors, such as ring patterns, node numbers, and T-O-T bridging angles (T = tetrahedral metal nodes in zeolites and ZIFs), is used as data filters to eliminate topologies infeasible for ZIF formation. Carefully chosen structural descriptors facilitate the prediction of plausible ZIF topologies. To investigate potential applications as porous ZIFs, this work performs hydrogen adsorption screening and suggested notable target ZIFs. The collection of new plausible ZIFs, derived from the combined descriptors, will be a structural blueprint for synthetic chemists.
Zeolite is an important porous solid in industry and is used in various fields such as gas separation, storage, and catalytic action. However, the pore size is not large, and it is not easy to control the chemical environment at the molecular level. Therefore, “ZIF,” a zeolite-mimicking porous solid, is emerging as a next-generation porous material.
A research team, led by Professor Wonyoung Choe in the Department of Chemistry at UNIST has succeeded in predicting the structure of zeolitic imidazolate frameworks (ZIFs), a type of metal-organic porous solids (MOFs). ZIF is a material that can control both the chemical environment of pores through chemical functional groups and the structural properties of zeolite.
Zeolite has more than 2 million crystal structures by connecting the basic bond form of the tetrahedron (SiO4). Nevertheless, only 250 zeolites have been discovered or synthesized so far. In academia, the difficulty of synthesizing zeolite of a new structure is called a zeolite mystery. The research team began the study by paying attention to the similar application of these mysteries in ZIF.
Figure 1. Flow chart for finding topology candidates for ZIFs from zeolites databases. 2 million zeolite structures were sequentially filtered with the descriptors (blue diamond), node number, vertex symbol, and T-O-T angle. The number of zeolite structures passing through the descriptors is displayed in the yellow boxes. The grey hexagon represents excluded zeolite topologies. The A, B, C, and D in yellow boxes represent the number of the following topologies.
In this work, the research team proposed a combination of intuition-based structural descriptors, node number, vertex symbol, and T-O-T angle, leading to the discovery of a set of 207 plausible ZIFs. When those parameters were used as collective descriptors, the research team efficiently identified 207 new hypothetical ZIFs among the two million zeolitic topologies through energy calculations based on density functional theory (DFT). According to the research team, some of those new ZIFs showed promising and high hydrogen deliverable capacity, exceeding the ultimate DOE target.
“Conventional materials discovery heavily relies on synthetic efforts through repeated trial-and-error experiments,” said Professor Choe. “With the help of a blueprint in hand for ZIF construction, together with targeted synthetic efforts, we expect to see a new stream of ZIFs with superior functions in the foreseeable future.”
The findings of this research have been available online in the February 2023 issue of Small, ahead of its publication. This study has been supported by the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (MSIT). It has been also supported by the Carbon Neutral Institute Fund of UNIST.
eom, J., Choe, A., Lee, J. et al., “Photosensitive ion channels in layered MXene membranes modified with plasmonic gold nanostars and cellulose nanofibers.” Nat. Commun., (2023).