For the first time, we designed and synthesized a new kind of ionic metal-organic framework with lanthanide ions and a carboxyl-functionalized ionic liquid, including [Er(4)(mu(3)-OH)(4)(mu(2)-O)(0.5)OL(4)(H(2)O)(3)] x Br(2.90) x Cl(1.10) x 2 H(2)O (MOF-1) and [PrL(H(2)O)(4)Cl] x Br x H(2)O(MOF-2).