Two new metal-organic frameworks (MOFs), namely, three-dimensional poly[diaquabis{ 2 -1,4-bis [(2-methyl-1H-imidazol-1-yl)methyl]benzene}bis( 2 -glutarato)dinickel(II)] monohydrate], {[Ni 2 (C 5 H 6 O 4 ) 2 (C 16 H 18 N 4 ) 2 (H 2 O) 2 ]ÁH 2 O} n or {[Ni 2 (Glu) 2 (1,4-mbix) 2 (H 2 O) 2 ]ÁH 2 O} n , (I), and two-dimensional poly[[{ 2 -1,4bis[(2-methyl-1H-imidazol-1-yl)methyl]benzene}( 2 -glutarato)zinc(II)] tetrahydrate], {[Zn(C 5 H 6 O 4 )(C 16 H 18 N 4 )]Á4H 2 O} n or {[Zn (Glu)(1,4-mbix)]Á4H 2 O} n (II), have been synthesized hydrothermally using glutarate (Glu 2À ) mixed with 1,4bis[(2-methyl-1H-imidazol-1-yl)methyl]benzene (1,4-mbix), and characterized by single-crystal X-ray diffraction, IR and UV-Vis spectroscopy, powder X-ray diffraction, and thermogravimetric and photoluminescence analyses. Ni II MOF (I) shows a 4-connected 3D framework with point symbol 6 6 , but is not a typical dia network. Zn II MOF (II) displays a two-dimensional 4 4 -sql network with onedimensional water chains penetrating the grids along the c direction. The solidstate photoluminescence analysis of (II) was performed at room temperature and the MOF exhibits highly selective sensing toward Fe 3+ and Cr 2 O 7 2À ions in aqueous solution. research papers Acta Cryst. (2020). C76, 148-158 Zhao et al. Two Ni II and Zn II metal-organic frameworks 149 research papers Acta Cryst. (2020). C76, 148-158 Zhao et al. Two Ni II and Zn II metal-organic frameworks 157

Two new CdII MOFs, namely, two-dimensional (2D) poly[[[μ2-1,4-bis(1H-benzimidazol-1-yl)butane](μ2-heptanedioato)cadmium(II)] tetrahydrate], {[Cd(C7H10O4)(C18H18N4)]·4H2O} n or {[Cd(Pim)(bbimb)]·4H2O} n (1), and 2D poly[diaqua[μ2-1,4-bis(1H-benzimidazol-1-yl)butane](μ4-decanedioato)(μ2-decanedioato)dicadmium(II)], [Cd2(C10H16O4)2(C18H18N4)(H2O)2] n or [Cd(Seb)(bbimb)0.5(H2O)] n (2), have been synthesized hydrothermally based on the 1,4-bis(1H-benzimidazol-1-yl)butane (bbimb) and pimelate (Pim2−, heptanedioate) or sebacate (Seb2−, decanedioate) ligands. Both MOFs were structurally characterized by single-crystal X-ray diffraction. In 1, the CdII centres are connected by bbimb and Pim2− ligands to generate a 2D sql layer structure with an octameric (H2O)8 water cluster. The 2D layers are further connected by O—H...O hydrogen bonds, resulting in a three-dimensional (3D) supramolecular structure. In 2, the CdII centres are coordinated by Seb2− ligands to form binuclear Cd2 units which are linked by bbimb and Seb2− ligands into a 2D hxl layer. The 2D layers are further connected by O—H...O hydrogen bonds, leading to an 8-connected 3D hex supramolecular network. IR and UV–Vis spectroscopy, thermogravimetric analysis and solid-state photoluminescence analysis were carried out on both MOFs. Luminescence sensing experiments reveal that both MOFs have good selective sensing towards Fe3+ in aqueous solution.