FLUORINATED POROUS MATERIALS: FROM METAL-ORGANIC FRAMEWORKS TO MOLECULAR CRYSTALS

ΠPorous materials have numerous applications, most of which are related to energy and fuels. The field of
porous materials has grown rapidly during the past two decades by the development metal-organic
(MOFs) and covalent organic frameworks (COFs). These modularly synthesized materials offer
essentially infinite possibilities for structural variation, and therefore allow the preparation of materials
with tailored thermal and chemical stabilities, pore sizes, shapes, and internal functionalities. However,
COFs and MOFs are not perfect: as insoluble solid-state structures, they have essentially no solution
processability, and many of MOFs and COFs are also hydrolytically sensitive. Work in my group has made
significant strides towards addressing both of these challenges by creating porous molecular crystals, in
which individual building blocks are held together only by noncovalent interactions: hydrogen bonding
and [Π···Π] stacking. These structures are fundamentally interesting and quite rare—molecules prefer to
closely pack in the solid state. At the same time, these materials promise to be practical, since they are
soluble, easily characterized, and highly thermally, hydrolytically, and chemically stable. In addition, their
noncovalent connections can expand or shrink in response to adsorbed analytes, thus constituting a
piezochromic sensing mechanism. These structures have been used as adsorbents for fluorinated
pollutants, hydrocarbons, and anesthetics. In this presentation, I will survey our research results in this
area, and also describe two other classes of porous materials prepared by my group: fluorinated MOFs
and the emergent class of porous macrocycles known as cyclobenzoins, which can be synthesized in a
single step from commercially available starting materials.