Ni(II)-metal–organic frameworks based on 1,4-phenylenedipropionic acid: Solvothermal syntheses, structures, and photocatalytic properties

Abstract Four novel Ni(II)-metal–organic frameworks, namely [Ni(azp)(ppa)(H 2 O) 2 ] n ( 1 ), [Ni(tmdp)(ppa)(H 2 O) 2 ] n ( 2 ), {[Ni(bpetha)(ppa)]·1.7H 2 O} n ( 3 ), and {[Ni(bpy)(H 2 O) 4 ](ppa)} n ( 4 ) (azp = 4,4′-azodipyridine, H 2 ppa = 1,4-phenylenedipropionic acid, tmdp = 4,4′-trimethylenedipyridine, bpetha = 1,2-bis-(4-pyridyl)ethane, bpy = 4,4′-bipyridine) were synthesized and structurally characterized. With the differences in the length and flexibility of N,N ′-donor coligands, Ni(II)-MOFs with the diversities of structural architectures and coordination modes of dicarboxylate ppa ligand were obtained. Compound 1 is 2D (4,4)-grid sheet whereas 2 shows 2-fold interpenetrating 2D (4,4)-layers. Compound 3 exhibits 3-fold interpenetrating coordination 3D framework with the α-Po topology while 4 shows 1D chain. Remarkably, compounds 1 – 4 exhibit energy band gaps of 3.27, 3.66, 3.58 and 3.36 eV, respectively. The photocatalytic activities of these materials for degradation of methylene blue (MB) were investigated with the degradation efficiencies within 90 min of 96.8%, 64.4%, 67.4%, and 75.0% for 1 – 4 , respectively.