Noble-Metal-Free ZnII-Anchored Pyrene-Based Covalent Organic Framework (COF) for Photocatalytic Fixation of CO2 from Dilute Gas into Bioactive 2-Oxazolidinones

Abstract

Photocatalytic conversion of CO₂ into value-added chemicals offers a propitious alternative to traditional thermal methods, contributing to environmental remediation and energy sustainability. In this respect, covalent organic frameworks (COFs), are crystalline porous materials showcasing remarkable efficacy in CO₂ fixation facilitated by visible light owing to their excellent photochemical properties. Herein, we employed Lewis acidic Zn(II) anchored pyrene-based COF (Zn(II)@Pybp-COF) to facilitate the photocatalytic CO₂ utilization and transformation to 2-oxazolidinones. Notably, Zn-COF displayed absorption of visible light, with an optimal band gap of 1.8 eV, effectively catalyzing light-mediated functionalization of propargylic amines to 2-oxazolidinones under green conditions. Detailed experimental and theoretical mechanistic investigations demonstrated that light plays a decisive role in enhancing the efficacy of the photocatalyst, as it activates inert CO₂ molecule to radical anion and hence, decreases the energy barrier for its subsequent cyclization reaction with propargylic amine. Additionally, Zn-COF demonstrates promising catalytic performance utilizing dilute gas as the CO₂ source. This is the first report regarding noble metal-free, Zn-COF exhibiting excellent photocatalytic carboxylative cyclization of CO₂ with propargyl amines to prepare 2-oxazolidinones using dilute gas (13 % CO₂). This study offers a new direction for rationally constructing noble metal-free eco-friendly photocatalyst for achieving CO₂ fixation reactions under eco-friendly conditions.