The electrochemical properties, nitrogen adsorption, and photocatalytic activities of three 3D metal–organic frameworks bearing the rigid terphenyl tetracarboxylates ligands

Abstract

Three new three-dimensional (3D) metal–organic frameworks (MOFs) derived from terphenyl tetracarboxylates, namely, [Mn(H₂L)]_n (1), {[Ni₃(L)(μ₃-OH)₂(H₂O)₄]₂·3H₂O}_n (2) and {[(CH₃)₂NH₂]₂[Zn(L)]·2DMF}_n (3) (H₄L = [1,1′:4′,1′′-terphenyl]-2′,4,4′′,5′-tetracarboxylic acid), were synthesized and characterized by elemental analyses, IR spectra, thermogravimetric (TG) analyses, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. Complex 1 represents a 6-connected {4¹²·6³} framework, which contains 1D stair-type chain and 2D layer. Complex 2 displays the complicated {4¹¹·6¹²·8⁵}{4²·6}{4³·6³}{4³}{4⁴·6²}{4⁸·6⁶·8} topology, in which Ni–O chains play an important role in the whole framework. In complex 3, the wave-like and “H”-like 1D chains link each other to create the 3D architecture with {4²·8⁴} topology. The introduction of different metal ions and the diversities synthesis processes lead to the great differences of the final 3D frameworks. In addition, the fluorescence properties reveal that complex 3 containing Zn^II possesses a fluorescent intensity, and complexes 1–2 based on Mn^II and Ni^II have no florescent activity. The electrochemical properties show that complex 2 possesses electrocatalytic activity for the reduction of nitrite. Photocatalytic properties indicate that complex 1 has good catalytic activity for the degradation of methylene blue (MB). Nitrogen adsorption reveals that complex 3 has adsorption property for nitrogen at 77 K.