Herpes simplex viruses (HSVs) rely on capsid-associated tegument complex (CATC) for long-range axonal transport of their genome-containing capsids between sites of infection and neuronal cell bodies. ...Here we report cryo-electron microscopy structures of the HSV-1 capsid with CATC up to 3.5-angstrom resolution and atomic models of multiple conformers of capsid proteins VP5, VP19c, VP23, and VP26 and tegument proteins pUL17, pUL25, and pUL36. Crowning every capsid vertex are five copies of heteropentameric CATC, each containing a pUL17 monomer supporting the coiled-coil helix bundle of a pUL25 dimer and a pUL36 dimer, thus positioning their flexible domains for potential involvement in nuclear capsid egress and axonal capsid transport. Notwithstanding newly discovered fold conservation between triplex proteins and bacteriophage λ protein gpD and the previously recognized bacteriophage HK97 gp5-like fold in VP5, HSV-1 capsid proteins exhibit extraordinary diversity in forms of domain insertion and conformational polymorphism, not only for interactions with tegument proteins but also for encapsulation of large genomes.
Metal-organic frameworks (MOFs) have attracted considerable attention for various applications due to their tunable structure, porosity and functionality. In general, MOFs have been synthesized from ...isolated metal ions and organic linkers under hydrothermal or solvothermal conditions via one-spot reactions. The emerging precursor approach and kinetically tuned dimensional augmentation strategy add more diversity to this field. In addition, to speed up the crystallization process and create uniform crystals with reduced size, many alternative synthesis routes have been explored. Recent advances in microwave-assisted synthesis and electrochemical synthesis are presented in this review. In recent years, post-synthetic approaches have been shown to be powerful tools to synthesize MOFs with modified functionality, which cannot be attained via de novo synthesis. In this review, some current accomplishments of post-synthetic modification (PSM) based on covalent transformations and coordinative interactions as well as post-synthetic exchange (PSE) in robust MOFs are provided.
Switching in Metal–Organic Frameworks Bigdeli, Fahime; Lollar, Christina T.; Morsali, Ali ...
Angewandte Chemie,
March 16, 2020, Volume:
59, Issue:
12
Journal Article
Peer reviewed
Open access
In recent years, metal–organic frameworks (MOFs) have become an area of intense research interest because of their adjustable pores and nearly limitless structural diversity deriving from the design ...of different organic linkers and metal structural building units (SBUs). Among the recent great challenges for scientists include switchable MOFs and their corresponding applications. Switchable MOFs are a type of smart material that undergo distinct, reversible, chemical changes in their structure upon exposure to external stimuli, yielding interesting technological applicability. Although the process of switching shares similarities with flexibility, very limited studies have been devoted specifically to switching, while a fairly large amount of research and a number of Reviews have covered flexibility in MOFs. This Review focuses on the properties and general design of switchable MOFs. The switching activity has been delineated based on the cause of the switching: light, spin crossover (SCO), redox, temperature, and wettability.
A switch in time: Although dynamic and flexible metal–organic frameworks (MOFs) have been closely assessed in recent literature, analysis into the subcategory of switchable MOFs has been comparably lacking. By virtue of their steady rise in popularity, MOFs with intriguing, switchable responses to light, temperature, pressure, redox species and guests are surveyed.
The controlled generation of singlet oxygen is of great interest owing to its potential applications including industrial wastewater treatment, photochemistry, and photodynamic therapy. Two ...photochromic metal–organic frameworks, PC‐PCN and SO‐PCN, have been developed. A photochromic reaction has been successfully realized in PC‐PCN while maintaining its single crystallinity. In particular, as a solid‐state material which inherently integrates the photochromic switch and photosensitizer, SO‐PCN has demonstrated reversible control of 1O2 generation. Additionally, SO‐PCN shows catalytic activity towards photooxidation of 1,5‐dihydroxynaphthalene.
Back and forth: Through a classical pillar‐layer structure constructed with mixed linkers, two photochromic metal–organic frameworks, PC‐PCN and SO‐PCN, have been developed. SO‐PCN integrates a photochromic switch and photosensitizer, and has demonstrated reversible control of 1O2 generation (see figure).
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/Brønsted 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 (MOFs) with high resistance to harsh chemical environments are reviewed with regard to recent progress in their research and development. Fundamental mechanisms of MOF stability, the design and synthesis of stable MOF architectures, and their latest applications are summarized, providing a fundamental outline for the discovery of new stable MOFs.
The poor electrical conductivity of two‐dimensional (2D) crystalline frameworks greatly limits their utilization in optoelectronics and sensor technology. Herein, we describe a conductive ...metallophthalocyanine‐based NiPc‐CoTAA framework with cobalt(II) tetraaza14annulene linkages. The high conjugation across the whole network combined with densely stacked metallophthalocyanine units endows this material with high electrical conductivity, which can be greatly enhanced by doping with iodine. The NiPc‐CoTAA framework was also fabricated as thin films with different thicknesses from 100 to 1000 nm by the steam‐assisted conversion method. These films enabled the detection of low‐concentration gases and exhibited remarkable sensitivity and stability. This study indicates the enormous potential of metallophthalocyanine‐based conductive frameworks in advanced stand‐off chemical sensors and provides a general strategy through tailor‐make molecular design to develop sensitive and stable chemical sensors for the detection of low‐concentration gases.
A fully π‐conjugated and conductive 2D metallophthalocyanine framework with cobalt tetraaza14annulene linkages (see structure) exhibited high electrical conductivity of up to 0.52 S m−1 and a high carrier mobility of 0.15 cm2 V s−1. Thin films of the material with thicknesses of 100–1000 nm functioned as efficient chemiresistors and displayed high sensitivity and selectivity towards gases at low concentrations.
Development of a photosensitizing system that can reversibly control the generation of singlet oxygen (1O2) is of great interest for photodynamic therapy (PDT). Recently several ...photosensitizer–photochromic‐switch dyads were reported as a potential means of the 1O2 control in PDT. However, the delivery of such a homogeneous molecular dyad as designed (e.g., optimal molar ratio) is extremely challenging in living systems. Herein we show a Zr‐MOF nanoplatform, demonstrating energy transfer‐based 1O2 controlled PDT. Our strategy allows for tuning the ratios between photosensitizer and the switch molecule, enabling maximum control of 1O2 generation. Meanwhile, the MOF provides proximal placement of the functional entities for efficient intermolecular energy transfer. As a result, the MOF nanoparticle formulation showed enhanced PDT efficacy with superior 1O2 control compared to that of homogeneous molecular analogues.
A switch inside: In situ incorporation of a photosensitizing system into MOF nanoparticles to control 1O2 generation is possible using a tunable ratio of a photochromic switch. The MOF formulation allows enhanced in vitro photodynamic therapy (PDT) efficacy with a superior control of 1O2 production compared to a simple mixture of the dyad.
Highly stable porous polymer networks (PPNs) are synthesized through Yamamoto homocoupling reaction between tetrahedral monomers. Among those polymers, PPN‐4 shows exceptionally high Langmuir surface ...area of 10063 m2 g−1 (SABET: 6461 m2 g−1). It also exhibits ultra‐high hydrogen (158 mg g−1), methane (389 mg g−1), and carbon dioxide (2121 mg g−1) storage capacities. These properties make it a perfect adsorbent for clean energy applications.
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•MOFs-based sensors and their luminescent behaviors are described.•Luminescent MOFs for chemical sensing are summarized on the basis of various analytes.•MOF sensors for detecting ...variation of temperature are discussed.
Metal-organic frameworks (MOFs) are a fascinating class of highly porous materials composed of metal ions/clusters and organic linkers, which promise great potential in numerous fields. Recently, the use of MOFs as luminescent sensors has been extensively explored due to their unique crystallinity, tunable porosity and structural diversity. In this review, we intend to highlight some of recent studies in this active research area and update the database of various luminescent MOF-based sensors on the basis of different sensing targets including ions, organic molecules, and gases, and temperature.
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