25 Years of Reticular Chemistry Freund, Ralph; Canossa, Stefano; Cohen, Seth M. ...
Angewandte Chemie International Edition,
November 2, 2021, Volume:
60, Issue:
45
Journal Article
Peer reviewed
Open access
At its core, reticular chemistry has translated the precision and expertise of organic and inorganic synthesis to the solid state. While initial excitement over metal–organic frameworks (MOFs) and ...covalent organic frameworks (COFs) was undoubtedly fueled by their unprecedented porosity and surface areas, the most profound scientific innovation of the field has been the elaboration of design strategies for the synthesis of extended crystalline solids through strong directional bonds. In this contribution we highlight the different classes of reticular materials that have been developed, how these frameworks can be functionalized, and how complexity can be introduced into their backbones. Finally, we show how the structural control over these materials is being extended from the molecular scale to their crystal morphology and shape on the nanoscale, all the way to their shaping on the bulk scale.
Reticular chemistry translates the precision and expertise of organic and inorganic synthesis to the solid state. The most profound innovation of the field has been the elaboration of design strategies for the synthesis of extended crystalline solids through strong directional bonds. This Review highlights the classes of reticular materials, their functionalization, and the introduction of complexity into their backbones.
Among a plethora of nano‐sized therapeutics, metal‐organic frameworks (MOFs) have been some of the most investigated novel materials for, predominantly, cancer drug delivery applications. Due to ...their large drug uptake capacities and slow‐release mechanisms, MOFs are desirable drug delivery vehicles that protect and transport sensitive drug molecules to target sites. The inclusion of other guest materials into MOFs to make MOF‐composite materials has added further functionality, from externally triggered drug release to improved pharmacokinetics and diagnostic aids. MOF‐composites are synthetically versatile and can include examples such as magnetic nanoparticles in MOFs for MRI image contrast and polymer coatings that improve the blood‐circulation time. From synthesis to applications, this review will consider the main developments in MOF‐composite chemistry for biomedical applications and demonstrate the potential of these novel agents in nanomedicine. It is concluded that, although vast synthetic progress has been made in the field, it requires now to develop more biomedical expertise with a focus on rational model selection, a major comparative toxicity study, and advanced targeting techniques.
Metal–organic frameworks (MOFs) are polymeric coordination networks that have recently proposed for drug‐delivery applications. The inclusion of guest materials into MOFs to make MOF‐composites adds further functionality to both diagnostics and therapeutic action. From synthesis to applications, this review considers the main developments in MOF‐composite chemistry and its contribution to the next generation of theragnostic nanomedicine.
We present a compact physics-based model of the current-voltage characteristics of graphene field-effect transistors, of especial interest for analog and RF applications where band-gap engineering of ...graphene could be not needed. The physical framework is a field-effect model and drift-diffusion carrier transport. Explicit closed-form expressions have been derived for the drain current continuously covering all operation regions. The model has been benchmarked with measured prototype devices, demonstrating accuracy and predictive behavior. Finally, we show an example of projection of the intrinsic gain as a figure of merit commonly used in RF/analog applications.
What was once broadly viewed as an impossibility—learning from experimental data in economics—has now become commonplace. Governmental bodies, think tanks, and corporations around the world employ ...teams of experimental researchers to answer their most pressing questions. For their part, in the past two decades academics have begun to more actively partner with organizations to generate data via field experimentation. Although this revolution in evidence-based approaches has served to deepen the economic science, recently a credibility crisis has caused even the most ardent experimental proponents to pause. This study takes a step back from the burgeoning experimental literature and introduces 12 actions that might help to alleviate this credibility crisis and raise experimental economics to an even higher level. In this way, we view our "12 action wish list" as discussion points to enrich the field.
MicroRNAs (miRNAs) are small, non-protein-coding RNA molecules that modulate gene translation. Their expression is altered in many central nervous system (CNS) injuries suggesting a role in the ...cellular response to stress. Current studies in brain tissue have not yet described the cell-specific temporal miRNA expression patterns following ischemic injury. In this study, we analyzed the expression alterations of a set of miRNAs in neurons and astrocytes subjected to 60 minutes of ischemia and collected at different time-points following this injury. To mimic ischemic conditions and reperfusion in vitro, cortical primary neuronal and astrocytic cultures prepared from fetal rats were first placed in oxygen and glucose deprived (OGD) medium for 60 minutes, followed by their transfer into normoxic pre-conditioned medium. Total RNA was extracted at different time-points after the termination of the ischemic insult and the expression levels of miRNAs were measured. In neurons exposed to OGD, expression of miR-29b was upregulated 2-fold within 6 h and up to 4-fold at 24 h post-OGD, whereas induction of miR-21 was upregulated 2-fold after 24 h when compared to expression in neurons under normoxic conditions. In contrast, in astrocytes, miR-29b and miR-21 were upregulated only after 12 h. MiR-30b, 107, and 137 showed expression alteration in astrocytes, but not in neurons. Furthermore, we show that expression of miR-29b was significantly decreased in neurons exposed to Insulin-Like Growth Factor I (IGF-I), a well documented neuroprotectant in ischemic models. Our study indicates that miRNAs expression is altered in neurons and astrocytes after ischemic injury. Furthermore, we found that following OGD, specific miRNAs have unique cell-specific temporal expression patterns in CNS. Therefore the specific role of each miRNA in different intracellular processes in ischemic brain and the relevance of their temporal and spatial expression patterns warrant further investigation that may lead to novel strategies for therapeutic interventions.
To gain insight into chiral recognition in porous materials we have prepared a family of fourth generation chiral metal–organic frameworks (MOFs) that have rigid frameworks and adaptable (flexible) ...pores. The previously reported parent material, Co2(S‐mandelate)2(4,4′‐bipyridine)3(NO3)2, CMOM‐1S, is a modular MOF; five new variants in which counterions (BF4−, CMOM‐2S) or mandelate ligands are substituted (2‐Cl, CMOM‐11R; 3‐Cl, CMOM‐21R; 4‐Cl, CMOM‐31R; 4‐CH3, CMOM‐41R) and the existing CF3SO3− variant CMOM‐3S are studied herein. Fine‐tuning of pore size, shape, and chemistry afforded a series of distinct host–guest binding sites with variable chiral separation properties with respect to three structural isomers of phenylpropanol. Structural analysis of the resulting crystalline sponge phases revealed that host–guest interactions, guest–guest interactions, and pore adaptability collectively determine chiral discrimination.
The chiral recognition mechanism of a family of chiral metal–organic materials was investigated towards the resolution of three racemic mixtures of phenylpropanol. X‐ray single‐crystal analysis of host–guest interactions revealed the specific binding sites with shape complementarity between the guest molecules and the adaptable chiral cavity.
Palm fatty acid distillate PFAD is an example of potential low-cost palm biofuel second generation feedstock, most used as a source of fatty acid for non-food applications in industry. Catalytic ...application of Oxone® salt was used in the present study for the esterification reaction of PFAD for biodiesel production for the first time. After optimizing the conversion rate, was possible to observe that, among the process variables studied Oxone® concentration (%), temperature (°C) and reaction time (h), Oxone® concentration was the only significant variable for the fatty acid ethyl esters (FAEEs) generation response variable. A > 90% conversion rate was reached with 15% Oxone® at 42 °C, using a PFAD:ethanol molar ratio of 1:5 at 12 h reaction time. The reaction system has a series of advantages, such as mild conditions, simple operation, green and high conversion. As alternative for make the biodiesel production as sustainable as possible.
Graphic Abstract
Abstract
Reticular materials are one of the more promising tools that humankind has developed to address the required energy transition. Despite their great potential showcased in the last decade, ...their use is so far mainly confined to the laboratory bench due to drawbacks derived from their powdery morphology. Unlike zeolites and activated carbons, the challenges in shaping and densification of reticular materials hamper their full implementation in the industry. Hence, strategies for shaping and integrating these materials need to be prioritized. Most of the existing strategies rely on applying mechanical pressure and adding chemical binders, but these approaches, although useful for shaping, diminish their final adsorption capacities and do not bring their theoretical, predicted performance. On the other hand, obtaining self‐shaped, dense bodies—so‐called monoliths—arises as a very promising and scalable alternative. Sol–gel monoliths are still scarce in the scientific literature despite their outstanding performance, particularly in terms of volumetric adsorption capacity. This review intends to help expand this scope by offering a rational guide on the self‐shaping of dense monoliths for reticular materials, as well as a complete revision of the state‐of‐the‐art in the field.
Ischemic stroke is the leading cause of serious, long-term adult disability and is associated with sensorimotor and cognitive impairments due to neuronal degeneration. Currently, recombinant tissue ...plasminogen activator (rTPA) is the only FDA-approved medical therapy for treatment of patients with acute ischemic stroke. However, rTPA can only be given within 3 hours of symptom onset, and only 2% of patients are eligible. Therefore, there is an urgent need for novel neuroprotective treatment options for ischemic stroke. An emerging treatment for a diverse range of neurological disorders associated with neurodegeneration is rapamycin, a key modulator of the mammalian target of rapamycin (mTOR) pathway. The mTOR pathway is the primary regulator of the cellular response to nutrient availability, changes in energy status and stress as seen following ischemia and reperfusion. However, rapamycin's effects on mTORC1 and mTORC2 are poorly understood in neurons. In the current study we show that rapamycin can prevent the activation of both mTORC1 and mTORC2 in cortical neurons and improve cell survival following oxygen glucose deprivation (OGD), an in vitro model of ischemic stroke. This work further supports the investigation of rapamycin as a novel neuroprotectant for ischemic stroke.
A new type of composite material involving the in situ immobilization of tin oxide nanoparticles (SnO2‐NPs) within a monolithic metal–organic framework (MOF), the zeolitic imidazolate framework ...(ZIF)‐8 is presented. SnO2@monoZIF‐8 exploits the mechanical properties, structural resilience, and high density of a monolithic MOF, while leveraging the photocatalytic action of the nanoparticles. The composite displays outstanding photocatalytic properties and represents a critical advance in the field of treating toxic effluents and is a vital validation for commercial application. Crucially, full retention of catalytic activity is observed after ten catalytic cycles.
A new type of composite material involving the in situ immobilization of photoactive tin oxide nanoparticles within a monolithic metal–organic framework, monoZIF‐8, is presented. SnO2@monoZIF‐8 displays outstanding photocatalytic properties with full retention of activity observed after ten catalytic cycles. This achievement represents a critical advance in the field of treating toxic effluents and is a vital validation for commercial applications.
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