Two new isomeric ZnII metal-organic frameworks (MOFs) based on mixed ligands, namely, poly[[μ-1,5-bis(2-methyl-1H-imidazol-1-yl)pentane-κ2N3:N3'](μ-5-methylisophthalato-κ2O1:O3)zinc(II)], [Zn(C9H6O4)(C13H20N4)]n, (I), and poly[[μ-1,5-bis(2-methyl-1H-imidazol-1-yl)pentane-κ2N3:N3'](μ3-5-methylisophthalato-κ3O1:O1':O3)(μ3-5-methylisophthalato-κ4O1:O1':O3,O3')dizinc(II)], [Zn2(C9H6O4)2(C13H20N4)]n, (II), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and thermogravimetric analysis. 
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