Issue Date: October 20, 2014
Organofluorine Framework Soaks Up Fluorocarbons
Chemists have created a fluorinated molecule that assembles into a porous material with a high affinity for certain greenhouse gases (Nat. Commun. 2014, DOI: 10.1038/ncomms6131). Thermally stable porous materials, such as metal-organic frameworks and covalent organic frameworks, have been around for decades. But coaxing molecules to form such structures noncovalently has been a challenge, says the University of Houston’s Ognjen Š. Miljanić. Even so, scientists have attempted the feat because such structures would have significant benefits: They would be lightweight, recyclable, and easily sublimed or deposited from solution. Noncovalent porous materials that scientists previously prepared suffered from instability in humid conditions because they relied on fragile boronic ester or imine functional groups. Miljanić’s team designed a fluorinated trispyrazole (shown) that assembles into a porous structure via π-π stacking of the aromatic rings and N–H∙∙∙∙N hydrogen-bonding interactions. The material is stable in the presence of water and can withstand temperatures up to 280 °C. It can also adsorb up to 75% of its own weight in fluorocarbons and chlorofluorocarbons used as refrigerants, which are potent greenhouse gases. Such a material could in theory be used as an adsorbent to soak up loose refrigerants in air-conditioning systems, Miljanić says.
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