In the quest for precise control of structure formation, researchers in the field of reticular chemistry have developed a novel technique inspired by the construction of arched stone windows. This technique utilizes a molecular version of an architectural arch-forming “centering formwork” template to guide the formation of metal-organic frameworks (MOFs) with tailored nanoscale windows. By manipulating the arrangement of supertetrahedra (ST) building blocks, researchers are able to create MOFs with pore windows of predetermined shape and size. This groundbreaking approach opens up new possibilities for the design and fabrication of MOFs with diverse applications ranging from gas separation to medical uses.
The starting point of this research was a zeolite-like MOF (ZMOF) with pentagonal windows framed by ST building blocks. The objective was to modify the ST arrangement and create new window shapes not previously reported. To achieve this, the research team developed centering structure-directing agents (cSDAs) that act as templates to control the alignment of ST and guide the formation of new ZMOFs with different window sizes and geometries. By tightening or expanding the angle between adjoining ST units, the researchers were able to create both narrow-windowed and large-windowed ZMOFs.
The size and volume of MOF pores play a crucial role in determining their applications. One notable discovery was a large-windowed ZMOF called Fe-sod-ZMOF-320, which exhibited the highest oxygen adsorption capacity among all known MOFs. This property makes it particularly valuable in industries such as medicine and aerospace, where increased oxygen storage or compact oxygen cylinders are desirable. Furthermore, other ZMOFs with narrow windows displayed potential for gas separation of molecular mixtures, highlighting their potential in the field of chemical separations.
The concept of cSDA offers several advantages that enhance MOF performance. The partitioning of large windows into smaller ones provides opportunities for more efficient chemical separations. Additionally, the increased internal pore surface area contributes to improved gas storage, while reinforcing the MOF framework enhances stability. This combination of benefits makes the centering approach a powerful strategy in reticular chemistry, offering the potential for tailored MOFs that address energy security and environmental sustainability challenges.
The innovative method of constructing tailored nanoscale windows in MOFs through the use of centering formwork templates represents a significant advancement in reticular chemistry. By precisely controlling the arrangement of ST building blocks, researchers have demonstrated the ability to design and fabricate MOFs with predetermined pore windows of various shapes and sizes. The applications of these tailored MOFs range from enhanced gas separation to improved oxygen storage, opening up new possibilities for energy and environmental technologies. The centering approach not only expands the repertoire of reticular chemistry but also holds promise for the development of custom-made MOFs to address pressing societal challenges.