Synthesis, Characterization, and Hydrogen Storage Enhancement of M_2(BDC)_2dabco with Palladium-Doped Activated Carbon

摘要

Two bi-organic type metal organic frameworks (MOFs) such as Co_2(BDC)_2dabco and Zn_2(BDC)_2 dabco have been synthesized by hydrothermal method and characterized along with hydrogen adsorption. The hydrogen adsorption capacity of these MOFs was increased after doping by palladium-activated carbon. Co_2(BDC)_2dabco has cracked and folded thin film like surface while Zn_2(BDC)_2dabco has a brick-typed cubic structure with particle size about 10～15 μm identified by FE-SEM. The XRD patterns represents that both MOFs have the well crystalline structure. Nitrogen adsorption isotherms show that both structures have Type I adsorption isotherm with the BET specific surface area of 1,390 and 1,433 m~2 g~(-1) for Co_2(BDC)_2dabco and Zn_2(BDC)_2dabco, respectively. Pristine Co_2(BDC)_2dabco and Zn_2(BDC)_2dabco can store about 0.22 and 0.25 wt.% of H_2 measured at 298 K and 32 bar. This capacity was greatly enhanced by doping palladium-activated carbon to 0.31 and 0.41 wt.%, respectively. Moreover, both structures were also characterized by XANES/EXAFS. EXAFS spectra indicate that Co_2(BDC)_2dabco has the Co - O bond distance of 2.030 A with the coordination number of 4.2 while Zn_2(BDC)_2dabco has 2.015 A bond distance of Zn - O with the coordination number of 3.4.