Methane Storage in Paddlewheel-Based Porous Coordination Cages

Abstract

Although gas adsorption properties of extended three-dimensional metal−organic materials have been widely studied, they remain relatively unexplored in porous molecular systems. This is particularly the case for porous coordination cages for which surface areas are typically not reported. Herein, we report the synthesis, characterization, activation, and gas adsorption properties of a family of carbazole-based cages. The chromium analog displays a coordination cage record BET (Brunauer−Emmett−Teller) surface area of 1235 m2/g. With precise synthesis and activation procedures, two previously reported cages similarly display high surface areas. The materials exhibit high methane adsorption capacities at 65 bar with the chromium (II) cage displaying CH4 capacities of 194 cm3/g and 148 cm3/cm3. This high uptake is a result of optimal pore design, which was confirmed via powder neutron diffraction experiments.

A Multifunctional, Charge‐Neutral, Chiral Octahedral M12L12 Cage

“…High pressure data were collected at multiple temperatures for CO 2 , H 2 , CH 4 , and N 2 O. Uptake plots for methane and hydrogen follow similarly shaped curves (see Supporting Information) and the overall uptake volumes in cm 3 g −1 are 82 (273 K) and 172 (77 K), respectively (c.f. the recent CH 4 /cage record of 194 cm 3 g −1 at 65 bar for a Cr‐based cage) . CO 2 uptake plateaus at about 170 cm 3 g −1 (at ca.…”

“…Powder X‐ray diffraction (PXRD) after solvent exchange, evacuation and repeated sorption experiments confirms that the crystallinity of the sample remains largely unchanged (see Supporting Information). It remains relatively rare for discrete metal–organic cages to display permanent porosity, with retention of crystallinity, with recent notable examples including those of Yaghi, Furukawa, Bloch, Zhou, and the nanoballs of Batten …”

“…the recentC H 4 /cage recordo f 194 cm 3 g À1 at 65 bar for aC r-based cage). [16] CO 2 uptake plateaus at about1 70 cm 3 g À1 (at ca. 1700 kPa, 273 K, Figure 3).…”

“…Powder X-ray diffraction (PXRD) after solvent exchange, evacuation and repeated sorption experiments confirms that the crystallinity of the sample remainsl argely unchanged (see Supporting Information). It remains relativelyr are for discrete metal-organic cages to display permanent porosity,w ith retention of crystallinity,w ith recent notable examples including those of Yaghi, [14] Furukawa, [15] Bloch, [16] Zhou, [17] and the nanoballs of Batten. [18] N 2 uptake measurements give aB runauer-Emmett-Teller (BET) surfacea rea of 693 m 2 g À1 .L ow pressure uptake of CO 2 indicates incomplete sorption at the limits of the instrumentation (see Supporting Information), leadingt oh igh pressure experiments being performed to gauge whethert here was a pressure barriert oa ccess the pore space within the cages.…”

Synthesis, Crystal Structure, and Properties of a New Coordination Polymer Built from N/O-Donor Mixed Ligands

“…In the past decades, the crystalline material of coordination polymers (CPs) has become an expanding research topic, not only due to their fascinating architectures and captivating topologies [1][2][3], but also for their potent applications in the fields of luminescence [4], gas adsorption/separation [5], chemical sensors [6], heterogeneous catalysis [7], and so on. Because the coordination polymers are composed of the metal ion and organic ligands, that is, the nature of metal ion and organic ligands are most important factors for constructing targeted CPs with desired properties [8][9][10].…”