Molecular weight enlargement of homogeneous catalysts for enhanced recovery via organic solvent nanofiltration: A critical review

Abstract

Organic solvent nanofiltration (OSN), also known as Solvent resistant nanofiltration (SRNF), is an emerging technology for separating molecules in organic solvents, offering significant advantages over other separation techniques, including low solid waste generation and high energy efficiency. One of the critical factors that influence the performance of OSN membranes is the molecular weight of the catalysts used. However, over the last decade, it became evident that other physico-chemical factors, such as catalyst flexibility and polarity also affect the separation efficiency. This review critically examines the recent advances in the molecular weight enlargement of catalysts, typically through the tuning of ancillary ligands that coordinate onto the active metal centers, focusing on how these modifications affect the overall separation effectiveness in OSN. Key strategies for molecular weight enlargement, such as addition of bulky substituents, dendrimer formation, and use of macromolecular ligands, are analyzed in terms of their impact on catalyst retention and rejection efficiency. By providing a comprehensive overview of the current state of research, this review aims to guide future developments in the field and highlight the critical areas where further investigation is needed to optimize catalyst design for OSN applications.