Synthesis, characterization, and hydrogen storage enhancement of M2(BDC)2dabco with palladium-doped activated carbon.

Two bi-organic type metal organic frameworks (MOFs) such as Co2(BDC)2dabco and Zn2(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. Co2(BDC)2dabco has cracked and folded thin film like surface while Zn2(BDC)2dabco has a brick-typed cubic structure with particle size about 10-15 microm 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 m2 g(-1) for Co2(BDC)2dabco and Zn2(BDC)2dabco, respectively. Pristine Co2(BDC)2dabco and Zn2(BDC)2dabco can store about 0.22 and 0.25 wt.% of H2 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 Co2(BDC)2dabco has the Co--O bond distance of 2.030 A with the coordination number of 4.2 while Zn2(BDC)2dabco has 2.015 angstroms bond distance of Zn--O with the coordination number of 3.4.