Structures and properties of five metal–organic frameworks based on 3,3′,5,5′-azoxybenzenetetracarboxylic acid and different secondary building units

Abstract

Abstract Five new metal–organic frameworks (MOFs), named [Zn 2 (aobtc)(H 2 O) 4 ] ( 1 ), [Mn 3 (Haobtc) 2 (DMA) 2 (H 2 O) 2 ]·2H 2 O ( 2 ), [Co 3 (Haobtc) 2 (H 2 O) 4 ]·11H 2 O ( 3 ), [Co 3 (aobtc) 2 ]·Himi·H 3 O·3H 2 O ( 4 ), [Cd 2 (aobtc)(bpy)]·4.5H 2 O ( 5 ) (H 4 aobtc = 3,3′,5,5′-azoxybenzenetetracarboxylic acid, bpy = 4,4′-bipyridine, imi = imidazole), have been designed and syntheses. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra and TG analyses. The five compounds exhibit diverse secondary building units (SBUs) and show various structures with different porosity. Compound 1 is a two-dimensional (2D) layer with (4,4)- sql topology based on binuclear Zn cluster (SBU). Both compounds 2 and 3 possess 2D framework with (3,6)-connected kgd topology, based on trinuclear Mn and Co clusters, respectively. Compound 4 shows a 3D framework with (3,8)-connected flu topology, containing linear trinuclear Co clusters as 8-connected nodes. The 3D framework of Compound 5 is built from infinite Cd–O–Cd rod SBUs. The effects of stacking modes on the crystal architectures are discussed. The solid-state photoluminescence for 1 and 5 , the magnetic properties for 2 – 4 , and CO 2 adsorption for 3 were also investigated.