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posted by martyb on Saturday July 20 2019, @03:17AM   Printer-friendly
from the if-there-is-a-polymer-is-there-a-unimer,-too? dept.

Metal-organic frameworks (MOFs) are a special class of sponge-like materials with nano-sized pores. The nanopores lead to record-breaking internal surface areas, up to 7800 m2 in a single gram. This feature makes MOFs extremely versatile materials with multiple uses, such as separating petrochemicals and gases, mimicking DNA, hydrogen production and removing heavy metals, fluoride anions, and even gold from water—to name a few.

One of the key features is pore size. MOFs and other porous materials are classified based on the diameter of their pores: MOFs with pores up to 2 nanometers in diameter are called "microporous," and anything above that is called "mesoporous." Most MOFs today are microporous, so they are not useful in applications that require them to capture large molecules or catalyze reactions between them—basically, the molecules don't fit the pores.

So more recently, mesoporous MOFs have come into play, because they show a lot of promise in large-molecule applications. Still, they aren't problem-free: When the major focus in the field is finding innovative ways to maximize MOF surface areas and pore sizes, addressing the collapsing problem is top priority.

[...] After adding the polymer to the MOFs, their high surface areas and crystallinity were maintained even after heating the MOFs at 150°C—temperatures that would previously be unreachable due to pore collapse. This new stability provides access to many more open metal coordination sites, which also increases the reactivity of the MOFs.

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