About this Research Topic
The number of novel crystalline framework materials, in particular metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), is continually increasing. These materials employ the concept of reticular chemistry, which describes the connection of molecular building blocks (MBBs) to construct extended and crystalline open frameworks. The elegance of this approach produces a large degree of structural diversity and endless possibilities for tuning framework functionality, by rational selection and dynamic exchange of individual MBBs either pre- or post-synthetically. However, several studies have highlighted that certain framework properties can strongly differ even under comparable chemical composition. Lattice defects can produce unexpected catalytic activity, adsorption properties, and mechanical stability. These defects impact framework composition and can be used to engineer framework materials that deviate from their ideal framework behavior. In contrast, an increasing number of studies have now demonstrated that framework properties can also be manipulated by simply modifying the size and morphology of the crystals under identical chemical composition.
The effects of crystal size and morphology are a novel domain in the chemistry of extended framework materials, beyond the traditional picture of reticular chemistry and structural defects, allowing the manipulation of host-guest, chemical, and physical properties of materials without modification of chemical composition or the characteristics of individual molecular building blocks. However, there are limited studies in this field, leaving many questions yet unanswered:
What are the mechanisms responsible for the influence of crystal size and morphology on framework materials? How general are these phenomena? On what length scale do these effects occur? To what extent can the anisotropy of crystal morphologies alter the framework properties? How can these effects be characterized by experimental or computational methods? What are the strategies for employing these effects in enhancing framework materials for various applications?
This wide range of questions clearly illustrates the open challenge in this area and the tremendous opportunity for further understanding the effect of crystal size and morphology. We believe that these challenges can only be met by a diverse assembly of scientists from unique backgrounds and complementary fields. As such, we intend to highlight research toward these open questions and collect articles that address various features of crystal size and morphology on framework materials. We welcome submission of Original Research, Review, Mini-Review, and Perspective articles on themes including, but not limited to:
• Synthesis strategies to obtain framework materials with narrow crystal size distributions and targeted crystal morphologies
• New methods to accurately determine crystal size distributions and morphologies, with a special emphasis on crystal surface properties and structural defects
• Experimental investigations of chemical, physical, and host-guest properties as a function of crystal size and morphology
• Computational characterization of structural properties at various length scales toward the treatment of crystal size and morphology
• Development of computational methods to characterize crystal size and morphology
Keywords: crystal size, crystal morphology, framework materials, metal-organic frameworks, covalent organic frameworks
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