Hydrogen adsorption in lithium doped MIL-101 and MIL-53(Al) at 77 and 298 K up to 100 bar: effect of lithium concentration

Lithium doped MIL-101 and MIL-53(Al) was prepared by solution impregnation method from Metal-Organic Frameworks (MOFs), MIL-101 and MIL-53(Al) using lithium naphthalenide (C10H7Li) solution. The doping was repeated to get two different concentrations of lithium doped MIL-101 and MIL-53(Al) respectively. The powder X-ray diffraction studies of the doped materials showed that the framework crystallinity of the synthesized materials was not affected by lithium doping. However N2 adsorption–desorption studies at 77 K showed a decrease in the BET surface area and pore volume values as the concentration of Li ions increases inside the framework. Hydrogen adsorption–desorption measurements were performed in lithium doped MIL-101 and MIL-53(Al) samples both at 77 and 298 K under high pressure (up to 100 bar). The results obtained were original and also useful considering that the experimental studies of high pressure hydrogen adsorption in lithium doped MOFs are scarce. This study also showed that the hydrogen adsorption capacities of MIL-101 and MIL-53(Al) can be significantly enhanced by lithium ion doping but controlled doping of lithium is necessary for good adsorption capacities as higher concentration of lithium destroys the framework structure of the materials.