Nonporous Organic Solids Capable of Dynamically Resolving Mixtures of Diiodoperfluoroalkanes

Abstract

Halogen bonding has increasingly facilitated the assembly of diverse host-guest solids. Here, we show that a well-known class of organic salts, bis(trimethylammonium) alkane diiodides, can reversibly encapsulate alpha,omega-diiodoperfluoroalkanes (DIPFAs) through intermolecular interactions between the host's I- anions and the guest's terminal iodine substituents. The process is highly selective for the fluorocarbon that forms an I-...I(CF2)mI...I- superanion that is matched in length to the chosen dication. DIPFAs that are 2 to 12 carbons in length (common industrial intermediates) can thereby be isolated from mixtures by means of crystallization from solution upon addition of the dissolved size-matched ionic salt. The solid-state salts can also selectively capture the DIPFAs from the vapor phase, yielding the same product formed from solution despite a lack of porosity of the starting lattice structure. Heating liberates the DIPFAs and regenerates the original salt lattice, highlighting the practical potential for the system in separation applications.

An Adaptable and Dynamically Porous Organic Salt Traps Unique Tetrahalide Dianions

“…a,w-Bis(trimethylammonium)alkane dihalides [3] are nonporous materials by nature. The structure of anhydrous 1 b (determined from single-crystal XRD, see the Supporting Information) and its hydrate as well as of 1 a,c [10] confirm that this is also the case for our starting materials.…”

“…Structure determination of 3 c from powder XRD data: the data were indexed using the program ITO [20] to give a monoclinic unit cell (a = 26.08, b = 6.88, c = 5.65 , b = 95.58; V = 1010.3 3 ). The space group was assigned from systematic absences as C2m.…”

“…[2] We have already demonstrated the dynamic behavior of a,w-bis(trimethylammonium)alkane diiodides. These nonporous materials selectively take up a,w-diiodoperfluoroalkanes [3] by gas-solid processes driven by the halogen bond (XB), the noncovalent interaction in which halogen atoms behave as electrophilic species (electron density acceptors, Lewis acids). [4] In these structures, the two iodide anions pin the a,w-diiodoperfluoroalkane at each end by C À I···I À XBs.…”

Fluorocarbon adsorption in hierarchical porous frameworks

“…Fluorocarbons also have important environmental significance because of their long lifetime and high ozone depletion and global warming potential. Understanding the adsorption behaviour of fluorocarbons is of fundamental importance in specific applications such as separating mixtures [1][2][3] , developing thermally driven cooling devices 4 , etching dielectrics for integrated circuits and wastewater cleanup 5 .…”

On the opposite trends of correlations between interaction energies and electrostatic potentials of chlorinated and methylated amine complexes stabilized by halogen bond

“…One type of these interactions is halogen bond which plays a significant role in different fields such as crystal engineering [1][2][3][4][5], biomolecular systems [6][7][8], organic catalysis [9,10] or optoelectronics [11,12]. Halogen bond is an attractive interaction between the positively charged fragment of the electrostatic surface (σ-hole) on the halogen atom (Cl, Br, I) and the electronrich center (e.g., electron lone pair from nitrogen atom) [13,14].…”