Researchers at King Abdullah University of Science and Technology develop new MOF design method A centuries-old technique for building arched stone windows has inspired a new way to form customized nanoscale windows in porous functional materials - metal organic frameworks (MOFs) - which has potential applications in gas separation and medical fields. A molecular version of an architectural arch "centered template" is used to guide the formation of MOFs with apertures of predetermined shape and size.
New MOFs designed and fabricated using this approach range from narrow-porous materials with gas separation potential to macroporous structures with potential for medical applications due to their excellent oxygen adsorption capabilities.
"One of the most challenging goals in the design of new structures is precisely controlling the formation of structures," said Aleksandr Sapianik, a postdoc in Mohamed Eddaoudi's group who led the study. "For network chemistry (the assembly of molecular building blocks into porous crystalline materials, such as MOFs), the research team realized that the centering template concept might provide precise control."
The starting point for research is zeolite-like MOFs (ZMOFs), which typically have pentagonal windows framed by building blocks called supertetrahedrons (STs). "Our goal is to control the arrangement of STs from this well-known topology to one that has never been reported before using these building blocks," Sapianik said.
The research team developed central structure directing agents (cSDA) to control ST alignment and form ZMOF windows of new shapes and sizes. One set of cSDA is designed to tighten the angle between adjacent ST cells, thus forming a small window. Another set of cSDA aims to widen the angle between ST units, thus forming a larger window.
Marina Barsukova, a postdoctoral fellow in Eddaoudi's team, said: "MOF pore size and volume are important parameters that affect its application. A large-window ZMOF (Fe-sod-ZMOF-320) designed by the team shows the highest oxygen adsorption capacity among known MOFs. This property has important applications in medical and aerospace It is important in industry because the high capacity can increase the amount of oxygen stored in oxygen bottles, or make the oxygen bottles smaller and easier to transport. The same ZMOF also excels in storing methane and hydrogen, both of which are potential fuels. Other ZMOFs in the series with narrow windows have also shown potential in gas separation of molecular mixtures. "
Vincent Guillerm, a research scientist in Eddaoudi's group, said the cSDA concept offers several advantages that can improve the performance of MOFs. He said: "cSDA separates large windows into smaller windows, and our preliminary results show that this will aid chemical separation. It also provides additional internal pore surfaces, helping to improve gas storage, and strengthens the MOF framework, thereby improving the material's stability. The centralized approach we developed is another powerful strategy for network chemistry, offering great potential for on-demand manufacturing of MOFs for applications in the fields of energy security and environmental sustainability."