Theoretical Study on the Hydrogenolysis of Polyurethanes to Improve the Catalytic Activities

Abstract

The metal-catalyzed hydrogenolysis of polymers is important in waste recycling; however, it is limited by the harsh reaction conditions and the low activities of catalysts, especially for earth-abundant metal-based catalysts. Herein, we perform a comprehensive study on the hydrogenolysis of polyurethane model catalyzed by Fe-, Mn-, Ru-, and Ir-iPrMACHO pincer complexes and propose a cascade mechanism comprising two-level hydrogenolysis and the hydrogenation of formaldehyde. In addition, the substrates and ligands are modulated to improve the activities of chemical recycling to monomer. It is found that the pincer ligands could dissociate from the metal centers at high reaction temperatures and further result in the deactivation of catalysts. The rigid Fe and Mn catalysts with tetradentate cyclic ligands are designed following the guidance, and the computations suggest that those designed catalysts could have high stabilities and activities.

Biomimetic Frustrated Lewis Pair Catalysts for Hydrogenation of CO to Methanol at Low Temperatures

“…In accord with our previous theoretical studies, − this research was carried out with the DFT ω B97X-D method using the Gaussian 09 program . Geometries were optimized in a dichloromethane solvent using the 6-311G­(d,p) basis sets.…”

Unveiling Pre-Transmetalation Intermediates in Base-Free Suzuki–Miyaura Cross-Couplings: A Computational Study

“…In accordance with our previous theoretical studies on homogeneous catalytic reactions, − all computations in this study were carried out by the density functional theory method with ωB97X-D functional using the Gaussian 09 program . Geometries were optimized in the 1,4-dioxane solvent using the BS-I basis sets, where the 6-311G­(d,p) basis sets were used for nonmetal atoms and the SDD basis sets with effective core potentials were used for metal atoms. , The single-point energy refinements were further performed with BS-II basis sets, where the 6-311++G­(2d,p) basis sets were used for nonmetal atoms, and the SDD basis sets were used for metal atoms.…”