Metal-organic frameworks for highly efficient heterogeneous Fenton-like catalysis

Four mixed ligand coordination polymers based on the flexible bis(5,6-dimethybenzimidazole) and aromatic dicarboxylic acids, namely, [Co(L1)(bpdc)]n (1), {[Co(L1)(npht)]·05H2O}n (2), [Co(L2)(bpdc)]n (3), and [Co(L3)(bpdc)(H2O)]n (4) (L1 = 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H2bpdc = 4,4′-biphenyldicarboxylic acid, L2 = 1,3-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H2npht = 3-nitrophthalic acid, L3 = 1,1′-bis(5,6-dimethylbenzimidazole)methane) have been hydrothermally synthesized and structurally characterized Polymer 1 features a 3D three-fold interpenetrating dia array with a 4-connected 66 network, while 2 exhibits a 3D noninterpenetrated 3-connected framework with a 103-ThSi2 architecture 3 and 4 have two-dimensional 3-connected (63) and 4-connected (4462) topologies, respectively Complex 4 ultimately is extended into an unusual 3D (3,5)-connected seh-3,5-P21/c supramolecular network via O–H⋯O hydrogen bonding interactions The fluorescence and catalytic properties of the complexes for the degradation of the Congo red azo dye in a Fenton-like process are reported

Four cobalt(II) coordination polymers with diverse topologies derived from flexible bis(benzimidazole) and aromatic dicarboxylic acids: syntheses, crystal structures and catalytic properties

Three new metal–organic frameworks (MOFs) were obtained from a siloxane dicarboxylic acid (CX), 4,4′-bipyridyne (BPy) or 1,2-bis(4-pyridyl)ethylene (EBPy) and copper or cobalt acetates. The compounds were characterized by IR spectroscopy, powder X-ray diffraction, energy-dispersive X-ray fluorescence (XRF), thermogravimetric analysis (TGA), dynamic water vapor sorption (DVS), electron microscopy (TEM, SEM), UV–vis diffuse reflectance and fluorescence measurements. These hydrophobic MOFs acted as efficient catalysts in two processes occurring in aqueous media. The best result in alkaline decomposition of hydrogen peroxide was 90% conversion after 30 min. The catalytic activity in photodecomposition of Congo Red (CR) was followed in mild environmental conditions, i.e. under natural sunlight, without additional oxidation agents or pH adjustments. Unprecedented catalytic activity was found, especially for the Co complex with CX and EBPy, with discoloration efficiency of ca. 82% after 80 min of exposure to sunlight. The obtained results, in terms of rate constants and efficiency are comparable with those reported for other catalytic systems in photoreactors or in the presence of H2O2. The best catalyst was also tested in a Fenton-like process and it was found that the addition of H2O2 doubles the rate constant and increases the efficiency to 97%. On the other hand, the remaining waters after CR photodecomposition were analyzed by mass spectrometry (ESI–MS) and it was concluded that “cleaner” water is obtained when the MOFs are used without addition of H2O2.

Siloxane-based metal–organic frameworks with remarkable catalytic activity in mild environmental photodegradation of azo dyes

Exploring the effect of chain length of bridging ligands in cobalt(II) coordination polymers based on flexible bis(5,6-dimethylbenzimidazole) ligands: Synthesis, crystal structures, fluorescence and catalytic properties

Synthesis and characterizations of two bis(benzimidazole)-based cobaltous coordination polymers with high adsorption capacity for congo red dye

Two coordination polymers, namely {[Co2(L1)2(btec)]∙4H2O}n (1) and [Co(L2)(btec)0.5(H2O)]n (2) [L1 = 1,3-bis(5,6-dimethylbenzimidazole)propane, btec = 1,2,4,5-benzenetetracarboxylate, L2 = 1,2-bis(5,6-dimethylbenzimidazole-1-ylmethyl)benzene], have been synthesized and characterized by physicochemical and spectroscopic methods as well as single-crystal diffraction. The cobalt(II) atoms display different environments with a tetrahedral geometry in 1 and trigonal–bipyramidal geometry in 2. Both complexes show 2D layer structures with a rare binodal (3,4)-connected topology structure, named 3,4L13. Their catalytic activities were tested for the degradation of congo red azo dye in a Fenton-like process.

Jian Chen Geng

Papers

Two 2D cobalt(II) coordination frameworks with unusual binodal network topology: synthesis, structures, and catalytic properties