Polymer immobilized Fe(III) complex of 2-phenylbenzimidazole: An efficient catalyst for photodegradation of dyes under UV/Visible light irradiation

Fe(III) complex of 2-phenylbenzimidazole has been covalently anchored on polymer and characterized by elemental analysis, FT-IR, far-IR, BET surface area measurements, UV-Vis/DRS spectroscopy, thermo-gravimetric analysis and magnetic moment measurements by VSM which confirmed an octahedral environment around Fe(III) in the bound complex. The photocatalytic performance of this complex was evaluated in the photodegradation of dyes in presence of H2O2 as an oxidizing agent. Suitable reaction conditions have been optimized by considering the effects of various reaction parameters such as pH, oxidants, concentration of dye, H2O2 and catalyst for the maximum degradation of dye. The photodegradation was found to be 100 with complete mineralization in 150 min. The comparison of photocatalytic efficiency of the catalyst under visible light, sunlight and dark conditions are accomplished. Comparison between catalytic activity of the polymer-supported complex and unbound complex demonstrated that the polymer-supported complex was more active. Photocatalytic performance of PS-Fe(III)PBMZL was also compared with commercial TiO2 (P25). This heterogeneous complex retained its activity up to 8 runs. A tentative mechanism has been proposed. © 2017 King Saud University

Zeolite-Y encapsulated VO[2-(2′hydroxyphenyl)benzimidazole] complex: investigation of its catalytic activity towards oxidation of organic substrates

Zeolite-Y encapsulated VO(IV)2-(2′-hydroxyphenyl)benzimidazole (ohpbmzl) was synthesized by flexible ligand approach and characterized using various physico-chemical techniques such as elemental analysis, XRD, inductively coupled plasma-atomic emission, fourier transform infrared spectroscopy, UV–vis-diffuse reflectance and electron paramagnetic resonance spectroscopy, thermogravimetric analysis, BET surface area and cyclic voltammetry (CV). Based on the results a square pyramidal structure was suggested for the encapsulated complex. Shift in UV absorbance to higher wavelength and variations in the redox potential values compared to the non-encapsulated complex in CV confirmed the successful encapsulation of the complex in the zeolite matrix. The catalytic efficacy was investigated towards oxidation of phenol, styrene, cyclohexane and ethyl benzene in acetonitrile using H2O2 as oxidant. Influence of reaction parameters like catalyst and substrate concentration, substrate/H2O2 molar ratio, and temperature were investigated to optimize the reaction conditions for maximum substrate conversion and selectivity towards desired products using the encapsulated complex. The catalytic activity was compared with vanadyl exchanged zeolite-Y (VO-Y) and non-encapsulated complex. The encapsulated complex retained its stability up to 3 runs as confirmed by recycling studies. Mechanistic pathways were proposed for all the probe reactions

Encapsulation of Cu (II) [2-(2'-Hydroxyphenyl) benzimidazole]2 within Zeolite Nano-Cavity: Structural Properties and its Catalytic Activity towards Phenol and Styrene Oxidation

The Cu(opbmzl)2 [ohpbmzl = 2-(2′-hydroxyphenyl)benzimidazole] was encapsulated within the super-cage of zeolite-Na-Y through a facile ligand approach and characterized by various analytical techniques such as elemental analysis, X-ray diffraction, inductively coupled plasma-atomic emission, FT-IR, UV–vis-DRS and EPR spectroscopy, thermogravimetric analysis (TGA), BET surface area measurements, pore volume by Horvath-Kawazoe (HK) method and cyclic voltammetry (CV). The shifting of the absorption bands and changes in redox properties of intra-zeolite complex compared to non-encapsulated complex implicated that the zeolite matrix remarkably influenced the structure-electronic properties. The peak potentials of Cu(opbmzl)2-Y in cyclic voltammogram were independent of scan rates, further corroborating the intrazeolite mechanism for electron-transfer-pathway in the zeolite-Y. The catalytic activity of Cu-Y, non-encapsulated and encapsulated complex was evaluated for phenol and styrene oxidation. As very low selectivity and formation of tarry products (for phenol oxidation) prevailed with t-butyl hydroperoxide (TBHP), H2O2 was reported to be the reasonable oxidant for the probe reactions. The influence of reaction parameters such as catalyst dosage, substrate concentration, substrate: H2O2 mole-ratio, temperature, time and solvent effects were investigated in detail. All the reaction parameters investigated were very crucial in tuning the product selectivity and conversion efficiency. The encapsulated complex exhibited better catalytic activity and selectivity than the non-encapsulated complex for the probe reactions, associated with exceptional structural stability during the recycling process. From the results, it was derived that the reactions proceeded without the involvement of free radicals and the probable mechanistic pathways based on the intermediate complexes associated with Cu-O species were proposed tentatively