Chiral Reticular Chemistry toward Functional Materials Discovery and Beyond

Abstract

Reticular chemistry, pioneered by Omar Yaghi, is concerned with linking molecular building blocks into porous crystalline 2D or 3D architectures through coordination bonds (metal–organic frameworks, MOFs) or covalent bonds (covalent organic frameworks, COFs). The successful marriage of inorganic and organic chemistry in MOFs has provided vast combinations amenable to manufacturing enormous solid materials (>100,000 in Cambridge Crystallographic Data Centre) with atomic precision. Benefiting from the immanent component and structural diversity, as well as the accessible nanometer-scale spaces within which various matter can be manipulated and controlled, the reticular framework materials have in effect not only facilitated the development of basic chemistry but also revolutionized various fields of applications including gas storage and separation, heterogeneous catalysis, heat allocation, sensors, photovoltaics, fuel cells, and biomedicine, to just name a few. One particularly intriguing subset of reticular frameworks concerns those that have chiral elements or characteristics, which represent a unique class of extended porous solids that can implement enantiomerically selective applications and beyond. However, the development of this field is still at the embryonic stage as compared with that of achiral reticular frameworks. Herein, we summarize the progress in the development of “chiral reticular chemistry” through which a serial of homochiral or racemic reticular frameworks with novel topologies and functions can be targeted. To begin, we introduce the background of reticular chemistry and the potential of using chiral building blocks to assemble reticular frameworks, particularly MOFs. In the following section, we describe the synthetic diversity and complexity using enantiopure or racemic ligands and highlight the important role of enantiopurity engineering in affecting the ultimate products. To be more specific, we present (i) isotopological synthesis in which enantiopure or racemic ligands produce frameworks with the same net topology, where the racemic ligands form either racemic frameworks or conglomerates; (ii) intrinsically chiral net-dominated synthesis in which enantiopure or racemic ligands can form different underlying topologies or undergo distinct crystallization pathways; (iii) other atypical syntheses that typically come by way of serendipity, where the assembly mechanism is highly elusive (for example, the enantiomeric ligands of opposite chirality give rise to entirely different structures). Next, we discuss the applications of these unique reticular framework materials that are otherwise unachievable by conventional achiral materials or analogues, aiming to underline the unique role of chiral building blocks in reticular chemistry. Last, we point out future research directions of “chiral reticular chemistry”. Our Account aims to highlight the importance of chirality as a decisive parameter to control the ultimate structure and function of periodic framework materials, which is largely overlooked in the history of reticular chemistry development. Through this comprehensive overview, we hope to spark future research interest in this emerging and fertile field, yielding new discoveries and innovations from the chemistry and material perspectives.