The potential of organic polymer-based hydrogen storage materials

Abstract

The challenge of storing hydrogen at high volumetric and gravimetric density for automotive applications has prompted investigations into the potential of cryo-adsorption on the internal surface area of microporous organic polymers. A range of Polymers of Intrinsic Microporosity (PIMs) has been studied, the best PIM to date (a network-PIM incorporating a triptycene subunit) taking up 2.7% H(2) by mass at 10 bar/77 K. HyperCrosslinked Polymers (HCPs) also show promising performance as H(2) storage materials, particularly at pressures >10 bar. The N(2) and H(2) adsorption behaviour at 77 K of six PIMs and a HCP are compared. Surface areas based on Langmuir plots of H(2) adsorption at high pressure are shown to provide a useful guide to hydrogen capacity, but Langmuir plots based on low pressure data underestimate the potential H(2) uptake. The micropore distribution influences the form of the H(2) isotherm, a higher concentration of ultramicropores (pore size <0.7 nm) being associated with enhanced low pressure adsorption.

Mechanical characterisation of polymer of intrinsic microporosity PIM-1 for hydrogen storage applications

“…4. This isotherm shares many qualities with those previously reported, namely the combination of IUPAC Type I and Type IVa behaviour, displaying strong porosity in both the microporous (pore diameter\2 nm) and mesoporous (pore diameter 2-50 nm) ranges [18,22,27]. This combination of behaviour is seen in the sharp rise in uptake in the low P/P 0 range, followed by a more linear rise through the middle of the isotherm.…”

“…This combination of behaviour is seen in the sharp rise in uptake in the low P/P 0 range, followed by a more linear rise through the middle of the isotherm. This isotherm displays very large hysteresis in the desorption curve, which is commonly seen for PIM-1 isotherms, and is likely indicative either of 'throats' in the porosity (narrow channels that limit the passage of gas molecules), or pore swelling caused by the presence of the adsorbate [18,22].…”

“…The leading study on this matter is that of McKeown et al [9], who, building on previous work on this subject [10,22], demonstrated that the adsorptive hydrogen uptake of PIM-1 at 77 K to be 1.45 wt% at 10 bar. The desorption curve is described by Budd et al [22] as showing no significant hysteresis, although no desorption curve is presented with this data.…”

Polymers of Intrinsic Microporosity

“…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].…”

Polymers of Intrinsic Microporosity Derived from Novel Disulfone-Based Monomers

“…16 Recently, Budd and coworkers described a novel class of high free volume polymeric microporous materials termed "polymers of intrinsic microporosity" (PIM) whose rigid and randomly contorted structures decrease chain packing efficiently in the solid state. Hence, these materials have gained considerable attention for use in heterogeneous catalysis, 3,17a membrane separations, 17b, 18 and hydrogen storage 4,[19][20][21] and as adsorbents for organic compounds. 3,22 The most commonly reported such material having high molecular weight, termed PIM-1, is prepared from commercially available 5,5 0 ,6,6 0 -tetrahydroxy-3,3,3 0 ,3 0 -tetramethylspirobisindane (TTSBI) and 2,3,5,6-tetrafluoroterephthalonitrile (TFTPN) by an efficient double aromatic nucleophilic substitution (S N Ar) polycondensation.…”