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.