A Zn(II)-functionalized COF as a recyclable catalyst for the sustainable synthesis of cyclic carbonates and cyclic carbamates from atmospheric CO 2

• Published in: Organic & biomolecular chemistry Vol. 20; no. 8; pp. 1707 - 1722
• Main Authors: Sarkar, Somnath, Ghosh, Swarbhanu, Islam, Sk Manirul
• Format: Journal Article
• Language: English
• Published: England 23.02.2022
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/D1OB01938D

A simple covalent organic framework (COF) bearing β-ketoenamine units as a potential heterogeneous ligand for Zn -catalyzed fixation and transformation of CO into value-added chemicals is reported. Catalytic investigations convincingly demonstrated that the Zn -functionalized covalent organic framework (Zn@TpTta) exhibits perfect catalytic activity in the fixation of CO for diverse epoxides with various substituents under sustainable conditions. A variety of terminal epoxides and slightly more complicated disubstituted epoxides were transformed into the corresponding cyclic carbonates with satisfactory to excellent yields ( , 69 to 99% yield) upon exposure to CO (1 atm) under solvent-free conditions (sustainable approach). On the other hand, this Zn -loaded covalent organic framework also displayed excellent performance in facilitating atmospheric cyclizative CO capture, which led to the formation of diverse cyclic carbamates ( , 61 to 94% yield) from unsaturated amine systems using -iodosuccinimide (NIS) as an iodinating agent and PEG-400 as a biodegradable and green polymeric solvent under base-free conditions (sustainable approach). The newly synthesized COF-based catalyst, namely, Zn@TpTta, has been completely characterized by SEM (scanning electron microscopy), EDX (energy dispersive X-ray analysis), HRTEM (high-resolution transmission electron microscopy), BET (Brunauer-Emmett-Teller), PXRD (powder X-ray diffraction), XPS (X-ray photoelectron spectroscopy), ICP (inductively coupled plasma), . More intriguingly, the catalytic system could be recycled over five times without a noticeable loss of catalytic performance for both reactions. This study opens an avenue for the Zn(II) embedded COF as a promising platform for regulating regioselectivity.