A solvent-free method can replace building blocks in metal-organic frameworks (MOFs) with others that cannot be incorporated into the materials via conventional synthesis methods (Sci. Adv. 2020, DOI: 10.1126/sciadv.aax7270). The technique broadens the range of possible MOF compositions and can be used to customize the materials’ structures and other properties to suit targeted applications.
MOFs are crystalline materials composed of metal ions or clusters connected by organic linkers. Extreme surface area and other attributes are driving rapid development of MOFs for gas storage and separation and other applications.
Using standard methods, researchers have made thousands of MOFs by combining a variety of metals and organic linkers. But not all combinations work. Some reagents pose problems of solubility, stability, or crystallization. These limitations can sometimes be overcome by treating MOFs after synthesis with solutions containing components that replace building blocks in the crystals. These postsynthesis treatments are also limited, however, because they often depend on specific properties of reagents and solvents.
To bypass that shortcoming, a team led by Wanbin Li of Jinan University developed a simple, inexpensive vapor-phase procedure for swapping linkers in MOF crystals with functionalized linkers that cannot be incorporated in MOFs through conventional methods.
In a demonstration, the team controllably exchanged some of the linkers in ZIF-8, a well-studied MOF, with iodoimidazole linkers, forming MOFs with two types of linkers. They showed that the method works with other halogenated imidazoles and can be used to make custom MOFs with three or more types of linkers.