Harnessing the Utility of Mechanochemically Synthesized 2D Imine-Linked Covalent Organic Framework Doped with Nickel Nanoparticles for Solvent-Free CO<sub>2</sub> Conversion at Atmospheric Pressure
Shabnam Khan, Farasha Sama, Lolwah Tawfiq Alfuhaid, Bosirul Hoque, Aasif Helal
Abstract
The utilization strategy of CO 2 to value-added chemicals has seen a recent surge in the effort to combat carbon emissions using covalent organic frameworks (COFs) due to their extended ordered structures, adjustable porosity, and predictive design. However, the lack of straightforward synthesis without compromising the crystallinity and porosity of COF materials remained a bottleneck toward their environmentally benign fabrication, thereby limiting the potential applications in various arenas. To address these issues, we demonstrate a facile method for creating crystalline and porous COF in minutes using the mechanochemical (MC) grinding approach using mortar and pestle. Herein, this easily scalable TFPCPa-COF(MC) was utilized for doping with non-noble nickel nanoparticle to give modified COF catalyst for the solvent-free CO 2 conversion under moderate conditions. The as-prepared Ni@TFPCPa-COF(MC) catalyst was characterized in detail, and it displayed a micromesoporous material with high surface area of 717 m 2 /g, layered-sheet morphology with ultrafine Ni nanoparticles (6–8 nm) confined in the layers through an interaction between nitrogen sites of triazine units and Ni nanoparticles. Importantly, Ni@TFPCPa-COF(MC) served as a heterogeneous catalyst for the conversion of epoxides with CO 2 to cyclic carbonates with a high conversion rate (98%) under solvent-free, ambient pressure (1 bar), and moderate temperature (50 °C) reaction conditions. Moreover, this catalyst can be effectively recycled for eight successive cycles with stable catalytic activity under optimized reaction conditions. All in all, the present work not only deals with the facile and efficient COF synthesis but also provides the application of mechanochemically synthesized COF doped with Ni nanoparticles in chemical conversion of CO 2, opening new horizons in preparing recyclable heterogeneous catalysts to alleviate the CO 2 utilization.