Metal–organic framework MIL-101 doped with palladium for toluene adsorption and hydrogen storage

Abstract

A series of Pd-doped MIL-101 samples with different Pd content and valence state have been prepared and employed as adsorbents for toluene adsorption and hydrogen storage for the first time. Compared with the parent MIL-101, PdCl₂-functionalized MOF exhibited remarkably increased adsorption capacity for toluene under both low and high vapor concentrations. The toluene uptake of the 3 wt% PdCl₂/MIL-101 at P/P₀ = 0.06 was ca. 660 mg g⁻¹ (i.e., 7.2 mmol g⁻¹), representing an enhancement of 450% over that of unmodified MIL-101. Moreover, the adsorption of toluene on the PdCl₂/MIL-101 sorbents was totally reversible. PdCl₂/MIL-101 could be simply reduced by NaBH₄ and hydrogen to prepare Pd nanoparticles immobilized on MIL-101. The hydrogen storage studies indicated that the reversible storage capacities on the Pd/MIL-101 samples at room temperature were enhanced by a factor of 1.5–2.3 compared with that of the parent MIL-101. It could be concluded that the size of the Pd nanoparticles and the Pd doping amount on the MIL-101 were crucial factors that determined the enhancement of the hydrogen storage capacity of the Pd/MIL-101 materials.