Two new microporous metal–organic frameworks, [Zn3(NH2BDC)3(H2O)2]·5DMF (1) and (Me2NH2)2[Cd3(NH2BDC)4]·2DMF·2.5 H2O (2) (NH2BDC = 2-amino-1,4-benzenedicarboxylate), based on linear trinuclear secondary building units of Zn3(COO)6 or Cd3(COO)8 that have different connected numbers, have been synthesized and characterized, which exhibit usual pcu and rare hex-like topologies, respectively. Both 1 and 2 are three-dimensional porous frameworks, having solvent accessible volumes of ca. 53 and 39%, respectively. There are unremovable guest Me2NH2+ cations clogged in the channels of 2. In contrast, being of good thermo-stability, 1 has a Langmuir surface area about 570 m2 g−1 and type I isotherm behaviour for nitrogen gas sorption at 77 K, being typical of microporous material.