A Novel Viologen-Derived Covalent Organic Framework Based Metal Free Catalyst for Nitrophenol Reduction

Abstract

It is highly desirable to develop new metal free catalysts to reduction of toxic organic pollutants such as 4-nitrophenol (4-NP). Viologens are efficient electron-transfer mediators (ETMs) for reduction reactions with NaBH4 as an effective hydrogen source. NaBH4-assisted reduction of 4-NP via a novel viologen-based covalent organic framework as metal free catalyst has been reported. The butyl bridge between the pyridine moieties at viologen based COF-TPCBP structure provides flexibility to the framework and gives the structure and amorphous character according to SEM, TEM and XRD results. The flexible 3D structure was also demonstrated by the geometric optimization. The structure without any metal moiety was fully completed to 4-NP reduction in only 12 minutes and have 88 % efficiency after 5 catalytic cycles because of the porous surface of the COF-TPCBP powder.