Mechanically pulverized covalent organic framework as a metal-free photocatalyst for fenton-like degradation of organic pollutants and hexavalent chromium reduction

Visible light active, metal-free heterogeneous photocatalysts are required to achieve sustainable and green chemical processes. Development of such a catalyst is reported here. Mechanical pulverization of a covalent organic framework (COF) resulted in enhanced visible light photocatalytic activity for environmental remediation. The pulverized COF have achieved the apparent quantum yield (AQY) up to 41% for photo-Fenton-like degradation of organic dyes. Photocatalytic activity of the pulverized COF is one of the highest amongst the metal-free catalysts reported so far. The photocatalyst can operate under a broad range of pH, unlike metal-based photocatalysts. The catalyst does not lose its activities on recycling over several cycles. The exceptional performance of the pulverized COF is due to the high dispersibility, efficient visible light absorption, and excellent charge mobility. Moreover, the photocatalyst have also been used in continuous flow photo-Fenton-like degradation. The photocatalytic space time yield (PSTY) in continuous flow was boosted by twenty-eight times than the conventional batch photocatalysis. Moreover, the pulverized COF showed an outstanding photocatalytic reduction of toxic hexavalent chromium (Cr⁶⁺) to non-toxic trivalent (Cr³⁺).