Metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) are open, crystalline supramolecular coordination architectures with porous facets. These chemically tailorable framework materials are the subject of intense and expansive research, and are particularly relevant in the fields of sensory materials and device engineering. As the subfield of MOF-based sensing has developed, many diverse chemical functionalities have been carefully and rationally implanted into the coordination nanospace of MOF materials. MOFs with widely varied fluorometric sensing properties have been developed using the design principles of crystal engineering and structure–property correlations, resulting in a large and rapidly growing body of literature. This work has led to advancements in a number of crucial sensing domains, including biomolecules, environmental toxins, explosives, ionic species, and many others. Furthermore, new classes of MOF sensory materials utilizing advanced signal transduction by devices based on MOF photonic crystals and thin films have been developed. This comprehensive review summarizes the topical developments in the field of luminescent MOF and MOF-based photonic crystals/thin film sensory materials.

Metal-organic frameworks: functional luminescent and photonic materials for sensing applications.

Metal-organic frameworks (MOFs) are an emerging class of porous materials with potential applications in gas storage, separations, catalysis, and chemical sensing. Despite numerous advantages, applications of many MOFs are ultimately limited by their stability under harsh conditions. Herein, the recent advances in the field of stable MOFs, covering the fundamental mechanisms of MOF stability, design, and synthesis of stable MOF architectures, and their latest applications are reviewed. First, key factors that affect MOF stability under certain chemical environments are introduced to guide the design of robust structures. This is followed by a short review of synthetic strategies of stable MOFs including modulated synthesis and postsynthetic modifications. Based on the fundamentals of MOF stability, stable MOFs are classified into two categories: high-valency metal-carboxylate frameworks and low-valency metal-azolate frameworks. Along this line, some representative stable MOFs are introduced, their structures are described, and their properties are briefly discussed. The expanded applications of stable MOFs in Lewis/Bronsted acid catalysis, redox catalysis, photocatalysis, electrocatalysis, gas storage, and sensing are highlighted. Overall, this review is expected to guide the design of stable MOFs by providing insights into existing structures, which could lead to the discovery and development of more advanced functional materials.

Stable Metal-Organic Frameworks: Design, Synthesis, and Applications.

Among the large family of metal–organic frameworks (MOFs), Zr-based MOFs, which exhibit rich structure types, outstanding stability, intriguing properties and functions, are foreseen as one of the most promising MOF materials for practical applications. Although this specific type of MOF is still in its early stage of development, significant progress has been made in recent years. Herein, advances in Zr-MOFs since 2008 are summarized and reviewed from three aspects: design and synthesis, structure, and applications. Four synthesis strategies implemented in building and/or modifying Zr-MOFs as well as their scale-up preparation under green and industrially feasible conditions are illustrated first. Zr-MOFs with various structural types are then classified and discussed in terms of different Zr-based secondary building units and organic ligands. Finally, applications of Zr-MOFs in catalysis, molecule adsorption and separation, drug delivery, and fluorescence sensing, and as porous carriers are highlighted. Such a review based on a specific type of MOF is expected to provide guidance for the in-depth investigation of MOFs towards practical applications.

Zr-based metal-organic frameworks: design, synthesis, structure, and applications.

Metal–organic frameworks (MOFs) are constructed from metal ions/clusters coordinated by organic linkers (or bridging-ligands). The hallmark of MOFs is their permanent porosity, which is frequently found in MOFs constructed from metal-clusters. These clusters are often formed in situ, whereas the linkers are generally pre-formed. The geometry and connectivity of a linker dictate the structure of the resulting MOF. Adjustments of linker geometry, length, ratio, and functional-group can tune the size, shape, and internal surface property of a MOF for a targeted application. In this critical review, we highlight advances in MOF synthesis focusing on linker design. Examples of building MOFs to reach unique properties, such as unprecedented surface area, pore aperture, molecular recognition, stability, and catalysis, through linker design are described. Further search for application-oriented MOFs through judicious selection of metal clusters and organic linkers is desirable. In this review, linkers are categorized as ditopic (Section 1), tritopic (Section 2), tetratopic (Section 3), hexatopic (Section 4), octatopic (Section 5), mixed (Section 6), desymmetrized (Section 7), metallo (Section 8), and N-heterocyclic linkers (Section 9).

Tuning the structure and function of metal–organic frameworks via linker design

Because of the high catalytic activities and substrate specificity, natural enzymes have been widely used in industrial, medical, and biological fields, etc. Although promising, they often suffer from intrinsic shortcomings such as high cost, low operational stability, and difficulties of recycling. To overcome these shortcomings, researchers have been devoted to the exploration of artificial enzyme mimics for a long time. Since the discovery of ferromagnetic nanoparticles with intrinsic horseradish peroxidase-like activity in 2007, a large amount of studies on nanozymes have been constantly emerging in the next decade. Nanozymes are one kind of nanomaterials with enzymatic catalytic properties. Compared with natural enzymes, nanozymes have the advantages such as low cost, high stability and durability, which have been widely used in industrial, medical, and biological fields. A thorough understanding of the possible catalytic mechanisms will contribute to the development of novel and high-efficient nanozymes, and the rational regulations of the activities of nanozymes are of great significance. In this review, we systematically introduce the classification, catalytic mechanism, activity regulation as well as recent research progress of nanozymes in the field of biosensing, environmental protection, and disease treatments, etc. in the past years. We also propose the current challenges of nanozymes as well as their future research focus. We anticipate this review may be of significance for the field to understand the properties of nanozymes and the development of novel nanomaterials with enzyme mimicking activities.

Nanozymes: Classification, Catalytic Mechanisms, Activity Regulation, and Applications

The construction of thousands of well-defined, porous, metal–organic framework (MOF) structures, spanning a broad range of topologies and an even broader range of pore sizes and chemical functionalities, has fuelled the exploration of many applications. Accompanying this applied focus has been a recognition of the need to engender MOFs with mechanical, thermal and/or chemical stability. Chemical stability in acidic, basic and neutral aqueous solutions is important. Advances over recent years have made it possible to design MOFs that possess different combinations of mechanical, thermal and chemical stability. Here, we review these advances and the associated design principles and synthesis strategies. We focus on how these advances may render MOFs effective as heterogeneous catalysts, both in chemically harsh condensed phases and in thermally challenging conditions relevant to gas-phase reactions. Finally, we briefly discuss future directions of study for the production of highly stable MOFs. Metal–organic frameworks (MOFs) have shown promise in a broad range of applications, including catalysis. In this Review, the chemical, thermal and mechanical stabilities of MOFs, in particular with catalytic uses in mind, are discussed.

Chemical, thermal and mechanical stabilities of metal–organic frameworks

A nerve-agent simulant based on a phosphate ester is hydrolyzed using a MOF-based catalyst. Suspensions of MOF-808 (6-connected), a material featuring 6-connected zirconium nodes, display the highest hydrolysis rates among all MOFs that have been reported to date. A plug-flow reactor was also prepared with MOF-808 (6-connected) as the active layer. Deployed in a simple filtration scheme, the reactor displayed high hydrolysis efficiency and reusability.

Instantaneous Hydrolysis of Nerve-Agent Simulants with a Six-Connected Zirconium-Based Metal–Organic Framework

Uncontrolled massive release of the primary greenhouse gas carbon dioxide (CO2) into atmosphere from anthropogenic activities poses a big threat and adversely affects our global climate and natural environment. One promising approach to mitigate CO2 emission is carbon capture and storage (CCS), in which ideal adsorbent materials with high storage capacity and excellent adsorption selectivity over other gases are urgently needed. For practical applications in CO2 capture from fl ue gas of power plants, the biggest single contributor of anthropogenic CO2 emission, the adsorbent materials must also be chemically stable, be easy to regenerate with minimal energy input, and be easily synthesized with low capital cost. Metal-organic frameworks (MOFs), highly crystalline porous materials constructed by metal ions and organic ligands, have emerged as a class of excellent adsor- bent materials for carbon capture. Great progress in MOF materials for CO2 capture has been made in the past and reviewed accordingly, but new discoveries are constantly being made as the fi eld quickly grows. In this paper, we provide a short review on the most recent advances in using MOFs for CO2 adsorption, storage, and separation that are directly related to CO2 capture. Some of the important properties of MOF adsorbents which are crucial for practical applications but are largely overlooked in research carried out so far are discussed. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd

Recent advances in carbon dioxide capture with metal‐organic frameworks

Catalytic degradation of chemical warfare agents and their simulants by metal-organic frameworks

The photooxidation of a mustard-gas simulant, 2-chloroethyl ethyl sulfide (CEES), is studied using a porphyrin-based metal–organic framework (MOF) catalyst. At room temperature and neutral pH value, singlet oxygen is generated by PCN-222/MOF-545 using an inexpensive and commercially available light-emitting diode. The singlet oxygen produced by PCN-222/MOF-545 selectively oxidizes CEES to the comparatively nontoxic product 2-chloroethyl ethyl sulfoxide (CEESO) without formation of the highly toxic sulfone product. In comparison to current methods, which utilize hydrogen peroxide as an oxidizing agent, this is a more realistic, convenient, and effective method for mustard-gas detoxification.

Yangyang Liu

Papers

Chemical, thermal and mechanical stabilities of metal–organic frameworks

Instantaneous Hydrolysis of Nerve-Agent Simulants with a Six-Connected Zirconium-Based Metal–Organic Framework

Recent advances in carbon dioxide capture with metal‐organic frameworks

Catalytic degradation of chemical warfare agents and their simulants by metal-organic frameworks

Selective Photooxidation of a Mustard-Gas Simulant Catalyzed by a Porphyrinic Metal–Organic Framework