Indirect Construction of Chiral Metal-Organic Frameworks for Enantioselective Luminescence Sensing.

Abstract

ConspectusChiral metal-organic frameworks (MOFs) are promising candidates as luminescent sensing materials for chiral species, which are essential components in modern industries, pharmaceuticals, and biological processes. The discrimination of enantiomers with highly similar physical and chemical properties is crucial because they are often present concurrently in the same system but may feature distinct effects on living matters. While the rapid and precise sensing capabilities of chiral MOFs outshine traditional detection methods for chiral species in daily life, chemical production, and the natural environment, it requires well-matched chemical and electronic structures between MOFs and chiral species. Yet, conventional strategies to construct chiral luminescent MOFs are immensely challenging due to the crystallization difficulties based on low-symmetric building blocks.Recent advancements in MOF chemistry have led to novel pathways for synthesizing chiral MOFs for enantioselective sensing. Compared with direct synthesis using optically pure luminescent ligands, which are usually complex and costly, indirect synthesis has garnered significant attention for reduced costs, simplified synthesis, enhanced material stability, and broad application scope. In the past few years, our group has developed chiral guest ion exchange, chiral coordination modification, and chiral defect engineering for indirectly synthesizing chiral MOFs. The chiral guest ion exchange is cost-effective for introducing chiral ions into MOF pores but can be applied only in charged frameworks. In addition, it also faces limitations in chiral ion availability and the tendency toward chirality loss during the sensing process. Besides, compared with ion exchange, the chiral coordination modification can maintain the chemical stability of chiral MOFs due to the stronger coordination bonds. Still, it requires MOFs with accessible open metal sites that may bind disordered dangling molecules, complicating structural determination. Therefore, specific pathways such as chiral linker installation with dual-end coordination have been developed to afford well-defined crystal structures. While all aforementioned methods may decrease the MOFs' pore sizes to a certain degree, we further developed a chiral defect engineering approach to enlarge pore size and introduce chiral center simultaneously. Such a highly competitive strategy is facile and low-cost and can be expanded to many well-known stable MOFs.In this Account, we delve into the intricate evolution of indirect strategies for constructing chiral MOFs tailored for enantioselective sensing applications. We provide a detailed analysis of the progression and innovation within the field, tracing the development of MOF-based enantioselective luminescence sensors. By systematically reviewing the various synthetic approaches, this work highlights their respective strengths and limitations. Beyond reviewing the state of the art, this Account offers forward-looking insights aiming to inspire the design and development of next-generation chiral luminescent MOFs. These advanced materials hold promise for versatile and impactful applications across enantioselective sensing and beyond.