Picolinohydrazide-Based Covalent Organic Polymer for Metal-Free Catalysis and Removal of Heavy Metals from Wastewater

Abstract

In this work, a picolinohydrazide-based covalent organic polymer (COP) is synthesized. COP acts as an efficient catalyst toward the Knoevenagel reaction between aromatic aldehydes and malononitrile at 30 °C. Apart from catalysis, COP could efficiently remove Ca2+, Cu2+, Cd2+, Hg2+, and Pb2+ ions from wastewater with an adsorption capacity of >600 mg g-1. Among these metal ions, Hg2+ is chosen for a detailed adsorption study. XPS, Raman spectroscopy, solid-state UV-vis spectroscopy, and density functional theory (DFT) analysis are performed to investigate the detailed interactions between Hg2+ and COP. From the various studies, it can be summarized that the pyridine groups of COP are involved in noncovalent interactions with Hg2+. Multifunctional COP is also responsible for removal of various other metal ions in a broad spectrum. Copyright © 2020 American Chemical Society.