Twelve isostructural rare earth metal–organic frameworks, namely, [Hmim][RE₂Cl(1,4-NDC)₃] (RE = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Y (12), Hmim = 1-hexyl-3-methylimidazolium, 1,4-NDCH₂ = 1,4-naphthalenedicarboxylic acid), have been ionothermally synthesized and structurally characterized. The structures feature three-dimensionally anionic frameworks of [RE₂Cl(1,4-NDC)₃]_nⁿ⁻ with channels in which the Hmim⁺ cations are located. The current results are the first ionothermal synthesis of rare earth metal–organic frameworks based on 1,4-NDCH₂ which possess a previously unknown (4,7)-connected 3-nodal network with the Schläfli symbol of (3²·4²·5²)(3²·4⁹·5²·6⁸)₂(4³·6³)₂. Luminescent and magnetic properties of some of the title compounds have been studied. Thermogravimetric analyses indicated that all these compounds were thermally stable up to ca. 250 °C.