ReviewApplications of reticular diversity in metal–organic frameworks: An ever-evolving state of the art
Graphical abstract
Introduction
Since its entrance in countless synthetic laboratories around the globe, the rational engineering of metal–organic frameworks (MOFs) approached more and more the process of building and furnishing a laboratory of its own [1]. As we decide the architecture of our workplace based on practicality and the positioning of the necessary equipment and furniture that allow a laboratory at the meter-scale to operate efficiently, when designing a new MOF structure we plan thoughtfully the division of confined spaces, their accessibility, and the installation of functional entities in what we estimate as optimal sites [2], [3]. There is, however, a rather obvious difference between setting up a laboratory at the meter and at the Ångström scale: the precision and reliability of the process of construction itself.
MOFs are assembled from an alternation of organic building units (OBUs) and metal-containing inorganic building units (IBUs) [3], [4] and the endless chemical variety of their constituents generates miscellaneous MOFs’ structures [5], [6], [7]. However, the very process of controlling such assembly remains perhaps the greatest and most long-standing challenge in researching these cutting-edge miniaturized laboratories [2]. Indeed, being MOFs synthesized by self-assembly instead of direct manipulation of their components, our approach to their construction remained substantially unchanged over the last decades and consists in driving the aggregation of building blocks by finely tuning synthesis variables such as temperature, solvent mixture, reactants, additives, etc. [8].
The practice of constantly perfecting and making more precise and reliable assembly of MOFs can be considered at the heart of their engineering and the primary source of their structural—hence functional—sophistication [9]. Major leaps in this respect included the attention shift from the systematic change of building blocks’ chemical structure to tuning linkers’ and framework’s metrics altogether (isoreticular MOFs [10]), to even regulating the framework’s mobility by employing conformationally-flexible linkers and/or geometrically versatile IBUs [11], [12]. Another more recent and increasingly popular area of MOFs chemistry is the engineering of partly aperiodic frameworks. It aims not only to achieve control on the crystalline structure of MOFs but also to purposefully introduce building-block vacancies [13] and heterogeneities [14], [15] with specific spatial distributions in the main crystal lattice.
Given this premise, herein we focus on the concept of ‘reticular diversity’ (Fig. 1), which we coined to describe the variability of structure and composition of framework assemblies. Reticular diversity is a key concept in MOFs chemistry as it does not only reflect the countless possibilities of synthesizing frameworks with different geometries, composition, complexity, metric and degree of order, but also includes the perspective of combining all these aspects in the design of a single extremely sophisticated material. Such an inclusive and open-minded approach to MOFs research is becoming a solid foundation of the most advanced realities in the field, and an exciting new source of innovation that lies largely unexplored.
With this in mind, we present an overview of recent applications (especially in the last 5 years) of MOFs’ reticular diversity in a comprehensive series of research areas.
Aiming to introduce the most relevant properties of MOFs, we start by describing the chemistry of their most crucial component: their pores. Subsequently, the major applications of MOFs as host–guest systems, sensors, electronic- and photonic materials, catalysts are extensively reviewed after providing, for each field, the basic theoretical background needed for a useful critical understanding. Each section also delivers the general context for its specific research field, the major challenges, and the state of the art, and finally presents a perspective look at the future possibilities of MOF materials.
Section snippets
Pore chemistry
The uniqueness of framework materials is their combination of functionality and regular porosity [2]. These two aspects are inextricably interdependent and affect one another. The application of the final material is governed by the physicochemical properties of the framework which, in turn, arise from their designed structural and chemical details. The origin of the macroscopic function can be traced back to the characteristics of the pore at the atomic scale. Hence, we can consider pore
Host–guest interactions
For many years, humanity has been curious to explain and understand various processes occurring in nature, driving research towards imitating and adapting these to their needs. Originating from scientific observation, through to the development of very complicated molecular theories, including the foundations of nanotechnology, knowledge in this area has expanded significantly. Specifically, growing global attention has seen devotion to research into processes occurring beyond the molecular
MOFs in chemical sensing
There is no area of industry where sensor enhancements are redundant and, as such, superior and more efficient chemical sensors are constantly pursued and desired [302], [303], [304], [305], [306]. The increasing importance of sensors is apparent from our evolutionary need for constant sensory awareness. Nowadays, technology is continuously developing and becoming an inseparable part of human life. As a growing technological generation, the desire for rapid communication of our personal,
MOFs as electronic and ionic conductors
Conductivity is a key feature for electronic devices and research into new conductive materials is fundamental for the development of modern technology. In the last 20 years the focus of technological advancement shifted towards micro and nano applications, revealing new challenges [404], [405], [406]. Recently, MOFs showed conductive properties that can be tuned and improved by applying rational design strategies and PSMs [407], [408], [409]. The scope of this chapter is to provide a broad
Artificial photosynthesis
Tremendous climate changes have occurred over the last years due to the constant release of carbon dioxide into our atmosphere as a consequence of the consumption of fossil fuels as the main source of energy. To stop this trend, new approaches to generate “clean and renewable” light and energy sources [477], including energy conversion and storage are key topics of current research. Several options for a CO2-neutral production of fuels have been discussed [478]. Artificial photosynthesis is one
Mofs in heterogeneous catalysis
The modern chemical industry, in particular, the refining, petrochemical, and plastics industries, is largely based on catalytic processes involving heterogeneous solid-state catalysts [649]. Catalysts facilitate the course of the chemical reactions by lowering the energy barrier of the cycle of changes taking place and thus increase the rate of the chemical reactions. The research on the synthesis of new catalysts with well-developed porosity and high surface area is carried out in a broad
Concluding remarks
By venturing into the vast landscape of MOFs applications, we presented a comprehensive—albeit not necessarily complete—overview of how reticular diversity projected MOFs into so many technological areas, where they are currently a class of materials of primary importance. As diversity is an intrinsically flexible and inclusive concept that evolves along with the discovery of unknown properties or unseen aspects of already-known ones, we encourage established and emerging scientists to embrace
CRediT authorship contribution statement
Aleksander Ejsmont: Writing - original draft, Visualization. Jacopo Andreo: Writing - original draft. Arianna Lanza: Writing - original draft. Aleksandra Galarda: Writing - original draft. Lauren Macreadie: Writing - review & editing. Stefan Wuttke: Writing - review & editing, Conceptualization, Supervision. Stefano Canossa: Writing - review & editing, Visualization. Evelyn Ploetz: Writing - original draft, Visualization. Joanna Goscianska: Writing - review & editing, Conceptualization,
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
References (752)
- et al.
Ionic metal-organic frameworks (iMOFs): Design principles and applications
Coord. Chem. Rev.
(2016) - et al.
Effect of pore size and shape on the thermal conductivity of metal-organic frameworks
Chem. Sci.
(2016) - et al.
Linker functionalized metal-organic frameworks
Coord. Chem. Rev.
(2019) - et al.
Approaches for synthesizing breathing MOFs by exploiting dimensional rigidity
Coord. Chem. Rev.
(2014) - et al.
Defect creation in metal-organic frameworks for rapid and controllable decontamination of roxarsone from aqueous solution
J. Hazard. Mater.
(2016) - et al.
Creation of mesoporous defects in a microporous metal-organic framework by an acetic acid-fragmented linker co-assembly and its remarkable effects on methane uptake
Chem. Eng. J.
(2018) - et al.
Engineering of coordination polymers for shape selective alkylation of large aromatics and the role of defects
Microporous. Mesoporous. Mater.
(2010) - et al.
Multivariate crystalline porous materials: Synthesis, property and potential application
Coord. Chem. Rev.
(2019) - et al.
Structural defects in metal–organic frameworks (MOFs): Formation, detection and control towards practices of interests
Coord. Chem. Rev.
(2017) - et al.
Hydrogen adsorption over Zeolite-like MOF materials modified by ion exchange
Int. J. Hydrogen Energy
(2010)