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

Photocatalytic conversion of CO 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 CO 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 CO 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 CO 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 CO source. This is the first report regarding noble metal-free, Zn-COF exhibiting excellent photocatalytic carboxylative cyclization of CO with propargyl amines to prepare 2-oxazolidinones using dilute gas (13 % CO). This study offers a new direction for rationally constructing noble metal-free eco-friendly photocatalyst for achieving CO fixation reactions under eco-friendly conditions.