Triptycene-Based Polymers of Intrinsic Microporosity: Organic Materials That Can Be Tailored for Gas Adsorption

Abstract

We report the synthesis and properties of network polymers of intrinsic microporosity (network−PIMs) derived from triptycene monomers that possess alkyl groups attached to their bridgehead positions. Gas adsorption can be controlled by the length and branching of the alkyl chains so that the apparent BET surface area of the materials can be tuned within the range 618−1760 m2 g−1. Shorter (e.g., methyl) or branched (e.g., isopropyl) alkyl chains provide the materials of greatest microporosity, whereas longer alkyl chains appear to block the microporosity created by the rigid organic framework. The enhanced microporosity, in comparison to other PIMs, originates from the macromolecular shape of the framework, as dictated by the triptycene units, which helps to reduce intermolecular contact between the extended planar struts of the rigid framework and thus reduces the efficiency of packing within the solid. The hydrogen adsorption capacities of the triptycene-based PIMs with either methyl or isopropyl substituents are among the highest for purely organic materials at low or moderate presures (1.83% by mass at 1 bar/77K; 3.4% by mass at 18 bar/77 K). The impressive hydrogen adsorption capacity of these materials is related to a high concentration of subnanometre micropores, as verified by Horvath−Kawazoe analysis of low-pressure nitrogen adsorption data.

Polymers for carrying and storing hydrogen

“…25 Polymer 3 was synthesized from triptycene subunits prepared through a dibenzodioxane formation reaction between hexahydroxyltriptycene and tetrafluoroterephthalonitrile. 26 Both polymers showed pore sizes in the range of 0.6-0.8 nm, which was indicative of ultramicroporosity. These insoluble network polymers had a high surface area and reversible hydrogen adsorption of ca.…”

“…These insoluble network polymers had a high surface area and reversible hydrogen adsorption of ca. 1.5 wt % at 0.1 MPa and 3.2 wt% at 1 MPa at 77 K. 25,26 With a similar strategy, a kind of star triptycene-based microporous polymer was synthesized via a cross-coupling reaction of trihalotriptycenes, which resulted in a surface area of ca. 2000 m 2 g − 1 and reversible hydrogen uptake of 1.93 wt% at 0.1 MPa and 77 K (4; Figure 1).…”

Polymers of Intrinsic Microporosity

“…At this point, it became apparent that a wide variety of microporous organic network polymers could be prepared by the general strategy of reacting appropriate fluorinated or chlorinated monomers with complementary monomers that contain multiple catechol units (i.e., 1,2-dihydroxybenzene) such as A1. Hence, a wide range of microporous network polymers have been prepared including those containing hexaazatrinaphthylene units for efficient metal-cation binding [43], bowl shaped cyclotricatechylene [44], and tribenzotriquinacene [45] units and triptycene units that provided high and controllable surface areas (up to 1730 m 2 g −1 ) [46,47]. These networks have been studied as potential hydrogen storage materials [44,[48][49][50][51] and as heterogeneous catalysts [20,22,[52][53][54].…”

Zr-Fumarate MOF a Novel CO2-Adsorbing Material: Synthesis and Characterization

“…CO 2 capture on solid sorbents such as metal oxides, zeolites, functionalized silicas, and carbon have drawn interest (Lee et al, 2002;Lin et al, 2009;Zhao et al, 2010). In addition, porous polymers with intrinsic microporosity and covalent organic polymers have gained attention due to their high surface area and CO 2 -capturing capacity (Budd et al, 2004;Germain et al, 2006;Liu et al, 2008;Ghanem et al, 2010;Bezzu et al, 2012). Metalorganic frameworks (MOFs) or porous coordination polymers are a class of novel materials constructed by metal and an organic ligand through a strong coordination bond.…”