Microenvironment modulation of Zr sites in covalent organic frameworks for low-pressure preparation of UHMWPE

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 47; pp. 32845 - 32854
• Main Authors: Li, Hao-Tian, Zhou, Tao, Peng, Yu-Qing, Shi, Xiao-Ke, Zhu, Zhi-Hao, Guan, Ye-Bin, Li, Yong-Qing, Liu, Zhen, Zhang, Chuan-Lei
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 09.12.2024
• Subjects: Catalysts; Channels; Contact pressure; Hydrogen bonding; Hydrogen bonds; Low pressure; Microenvironments; Molecular weight; Molecular weight distribution; Monomers; Polymerization; Polymers; Pressure effects; Receptor mechanisms; Triazine; Ultra high molecular weight polyethylene; Uniform flow; Zirconium
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d4ta04931d

The development of stabilized catalysts with one-dimensional meso-pore structures is important for advancing olefin polymerization. Covalent Organic Frameworks (COFs) are popular candidates for constructing single-site heterogeneous olefin polymerization catalysts due to their well-ordered structures and large channels. In this study, Zr-COF catalysts were applied for the first time to the production of ultra-high molecular weight ( M w = 1.71 × 10 6 g mol −1 ) linear polyethylene (UHMWPE) at 5 bar ethylene pressure, filling the gap of traditional catalysts for ethylene polymerization at low pressures. The microenvironment of nanoconfinement and electronic effects of Zr-COFs can directly affect the polymer properties, including product size, morphology, molecular weight and molecular weight distribution. Kinetic simulations show that a COF with a triazine ring skeleton can provide suitable receptors for forming hydrogen bonds to enrich ethylene monomers, leading to low-pressure ethylene polymerization. The continuous and uniform flow of monomers in the highly oriented channels lays a solid foundation for the full contact between the active centre and the monomer, which further facilitates the formation of conformational relationships. Zr-TtDa catalyst with a triazine ring in ethylene polymerization forms hydrogen bonds with ethylene, enriching it around metal sites. This method produced high molecular weight linear polyethylene ( M w = 1.71 × 10 6 g mol −1 ) at a low pressure (5 bar).