Crystal transformation in Mn(ii) metal–organic frameworks based on a one-dimensional chain precursor

Abstract

The solvothermal reaction of Mn(II) salts and 5-((4′-(tetrazol-5′′-yl)benzyl)oxy)isophthalic acid (H₃L) affords an Mn(II) based coordination polymer Mn(H₂L)₂(H₂O)₂ (1), which possesses a one-dimensional (1D) chain structure. Using 1 as the precursor, three Mn(II) metal–organic frameworks, Mn₃L₂(2,2′-bpy)₂·5H₂O (2), Mn₃L₂(H₂O)₄ (3), and Mn₄L₂(HL)(H₂O)₅·0.5H₂O (4), with three-dimensional (3D) networks can be obtained by different strategies of crystal transformation. Upon introduction of 2,2′-bipyridine (2,2′-bpy) as the ligand and 2,2′-biquinoline-4,4′-dicarboxylic acid as the structural-directing agent, 1 undergoes irreversible crystal transformation into 2 and 3, respectively, and 1 can be transformed into 4 by increasing the reaction temperature. Interestingly, the irreversible structural transformation of 3 into 2 can be carried out by adding a 2,2′-bpy ligand. Notably, after the removal of coordinated water molecules, 1 and 3 exhibit good catalytic performance for the cyanosilylation reaction even at 0 °C.