Zeolite-​encapsulated 2-​(o-​aminophenyl)​benzimidazole complexes: synthesis, characterization and catalytic activity

摘要

Cobalt(II)​, copper(II) and zinc(II) complexes of 2-​(o-​aminophenyl)​benzimidazole (AmPhBzlH) encapsulated in the super cages of zeolite-​Y and ZSM-​5 were synthesized and characterized by spectroscopic studies (IR, UV​/visible, EPR)​, elemental analyses, thermal studies and x-​ray diffraction patterns. The catalytic activity of encapsulated complexes was studied for the hydroxylation of phenol using 30​% H2O2 as an oxidant. Under optimized reaction conditions, the hydroxylation of phenol yielded catechol and hydroquinone as the major products. All catalysts show good selectivity for diphenol products. A max. conversion of phenol was obtained with [Cu(AmPhBzlH)​]​-​Y as the catalyst. Conversion of phenol varies in the order [Cu(AmPhBzlH)​]​-​Y > [Cu(AmPhBzlH)​]​-​ZSM-​5 > [Zn(AmPhBzlH)​]​-​Y > [Co(AmPhBzlH)​]​-​Y > [Zn(AmPhBzlH)​]​-​ZSM-​5 > [Co(AmPhBzlH)​]​-​ZSM-​5 after 6 h of reaction time. Test for the recyclability of the reaction was also carried out and the results indicate their recyclability.