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

摘要

MIL-101 is a chromium-based metal organic framework known to adsorb large amount of gases such as H2, CO2 and CH4. The framework was synthesized through solvothermal route and the H2 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 m2/g with a type I hysteresis loop measured from N2 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 Å and the coordination number of 5.4.