The hydrogen adsorption properties and uptake capacities of three-dimensional microporous materials of lantern-type dinuclear M(BDC)(DABCO)1⁄2 (M=CoII, CuII, and ZnII; BDC = 1,4-benzenedicarboxylate, DABCO = 1,4-diazabicyclo[2.2.2]octane; Co(BDC)(DABCO)1⁄2 (1), Cu(BDC)(DABCO)1⁄2 (2), Zn(BDC)(DABCO)1⁄2 (3)) were investigated at various temperatures of 77–333 K and pressures up to 10 MPa using a PCT automatic measuring system (Sievert-type apparatus). The results indicated that uptake to 4.11, 2.70, and 3.17 wt % of hydrogen can be stored on 1, 2, and 3, respectively, at 77 K. The amounts of hydrogen are adsorbed by all complexes at around room temperature (293 K) and high-pressures are much lower (<0.5 wt %). Adsorption isotherms at around room temperature show a linear uptake relationship; all of them follow the Henry’s law. By measuring nitrogen gas adsorption/desorption, all complexes exhibit approximately Type-I isotherms according to the IUPAC classification and possess BET surface areas in the range of 1165 (for 3) to 1595 m2 g−1 (for 1). Further, the thermal stability of all complexes is high, in the range of about 500 K (for 3) to 600 K (for 1). These complexes were synthesized and characterized by X-ray powder diffraction pattern, TG/DTA, FT-IR, surface area analysis, and hydrogen adsorption measurements.

A three-dimensional (3-D) cobalt coordination polymer Co(BDC)(DABCO)1⁄2 (BDC = 1,4-benzenedicarboxylate; DABCO = 1,4-diazabicyclo[2.2.2]octane), which has a novel lantern-type structure, was synthesized and characterized by X-ray powder diffraction patterns and elemental analysis. In addition, hydrogen-adsorption characteristics were evaluated at 77 K. The highest measured hydrogen uptake was 2.28 wt % at 77 K and 0.1 MPa for Co(BDC)(DABCO)1⁄2.

Abstract:We attempted synthesis of the hydrogen adsorption material suitable for the fuel cell vehicles (FCEVs). The designed and synthesized Cu 2 (3,5-Pyridinedicarboxylate) 2 (=Cu 2 PDC 2 ) metal complex showed an extremely high volumetric uptake density for a physisorption material, even though the specific surface area was only about 1,000 m 2 g −1 . Factors for high uptake properties are considered to be the increased adsorption sites per unit area, the increased adsorption energy, and the optimized design of pore shapes. High hydrogen uptake on volumetric basis is especially effective for FCEV because the tank volume is reduced. It is expected that property prediction using computational simulation and sophisticated analysis at the micro and nano levels will become an indispensable tool in the design of functional materials.

The behavior of hydrogen molecules adsorbed onto the nanospace of porous materials is of great interest but is poorly understood. Here we show direct visualization of deuterium molecules adsorbed on isoreticular metal organic frameworks ͑IRMOF-1͒ at 77 K using reverse Monte Carlo simulation based on first principle molecular dynamics simulation and neutron diffraction. Results show that the two types of adsorption sites around a ZnO 4 cluster are almost fully occupied by the deuterium molecules but that other sites are not fully occupied. Moreover an interesting information about the aggregation state of deuterium molecules was directly obtained from the deuteriumdeuterium partial pair distribution function. Namely, the average distance of deuterium molecules adsorbed onto IRMOF-1 is slightly longer than that in a solid state but much shorter than that in the corresponding gas state.

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