Synthesis, characterization, and hydrogen storage study by hydrogen spillover of MIL-101 metal organic frameworks

MIL-101 is a chromium-based metal organic framework known to adsorb large amount of gases such as H-2, CO2 and CH4. The framework was synthesized through solvothermal route and the H-2 adsorption capacity was measured using a standard gravimetric method. X-ray absorption spectroscopy was performed to understand the fine structure, neighbors, coordination number and bond distance. The BET specific surface area of MIL-101nf (treated with NH4F) was 2,868 m(2)/g with a type I hysteresis loop measured from N-2 adsorption isotherm. The hydrogen storage capacity was 0.16 wt% measured at 32 bar and room temperature for MIL-101nf. This capacity was increased up to 0.45 wt% by doping metal-supported carbon catalyst (Pd/AC and Pt/AC) through a carbon bridge with MIL-101. XANES spectra indicated that the valency of MIL-101 MOFs was Cr(III). EXAFS data also revealed that MIL-101 has a first shell of Cr-O bonding with the bond distance of 1.97 angstrom and the coordination number of 5.4.