A new acoustomicrofluidic method for synthesizing copper-based metal–organic frameworks is shown to yield novel large aspect ratio elongated crystal morphologies with high active metal site density on their surfaces, leading to enhanced conductivity.
Two-dimensional (2D) graphitic materials are often incorporated with metal–organic frameworks (MOFs) to compensate for the poor electrical conductivity of the latter, particularly if they are to be used for electrochemical...
Metal−organic frameworks (MOFs) have recently been shown to be effective antimicrobial agents, particularly if they comprise pathogenicidal metal ions. Nevertheless, the accessibility of these active metal sites to the pathogen, and hence the MOFs' antimicrobial activity itself, is often poor since the metal nodes are usually embedded deep within its three-dimensional (3D) structure. We show that a unique copper-based (copper(II)-benzene-1,3,5-tricarboxylate) MOF, whose quasi-two-dimensional (quasi-2D) swordlike structure facilitates exposure of the metal ions along its surface, exhibits enhanced antimicrobial properties against three representative plant pathogens: a bacterium (Pseudomonas syringae), a fungus (Fusarium solani), and a virus (Odontoglossum ringspot virus (ORSV)). Such superior antimicrobial activity results in low minimum inhibitory concentrations (MICs)half that of a commercial pesticide and an eighth of its conventional 3D cubic MOF counterpart (HKUST-1)and hence low phytotoxicity, which can be attributed to the accessibility of the surface copper sites to the pathogen, thereby facilitating their adhesion and physical contact with the MOF. Additionally, we observed that orchids treated with the quasi-2D MOF showed negligible phytotoxicity and 80% decreased viral load. This work constitutes the first study to demonstrate the antimicrobial properties of this novel MOF against bacterial, fungal, and viral plant pathogens, and the first chemical control of ORSV.
Despite its appeal of green H 2 production using energy from renewable sources, water electrolysis currently only accounts for a small percentage of global H 2 production due to the need for expensive electrocatalysts to compensate for Ohmic losses associated with the kinetic overpotential of the system. [4][5][6] At present, H 2 production via electrolysis is predominantly carried out in strong acidic/alkaline electrolytes using state-of-the-art platinum group metal (PGM) electrocatalysts, which enables hydrogen evolution reactions (HER) to be conducted at the lowest onset potential, albeit at practically insurmountable industrial costs due to the metal's scarcity. [7,8] To attain industrially-relevant current densities (200-500 mA cm −2 ), an overpotential between 1.8 and 2.5 V is typically required. [9] At these levels though, acidic electrolytes-while providing an abundant source of protons (H + ) and hydronium (H 3 O + ) ions-produce acid fog under high temperatures that can corrode the electrolyzer and contaminate the product. [10] Alkaline electrolysis, on the other hand, is commonly plagued by unstable electrocatalysts and the need for expensive pH-tolerant membranes. [11][12][13] It is therefore desirable to carry out electrolysis in neutral or near-neutral electrolytes (pH 5-9) with non-PGM electrocatalysts. [14] The HER rate under these conditions is, nevertheless, significantly lower than those for electrolytes with extreme pH levels. In addition to diffusion limitations, this is due to the rapid consumption of H 3 O + , which creates a bottleneck that limits the extent of reaction until higher overpotentials are able to drive H 2 O reduction. [10,[15][16][17] Even with the best electrodes (i.e., PGMs), H 2 production is several orders of magnitude lower under neutral conditions, [7] such that the overpotential required to reach a current density of −4 mA cm −2 exceeds 0.25 V in a 0.1 M KClO 4 electrolyte compared to as little as 30 mV in 0.5 M H 2 SO 4 . [18,19] Similarly poor performance is obtained with the use of nickel-based electrocatalysts, which are generally favored for alkaline conditions, given their affinity for OH − adsorption. [20] To circumvent these limitations, novel electrocatalysts have been designed, in which the electrode is doped to tailor its catalytic sites for both H* and OH* adsorption to complement the electrolytic conditions, [21][22][23] or through the introduction of complex architectures that facilitate more favorable local pH environments, [24] although these strategies A novel strategy utilizing high-frequency (10 MHz) hybrid sound waves to dramatically enhance hydrogen evolution reactions (HER) in notoriously difficult neutral electrolytes by modifying their network coordination state is presented. Herein, the practical limitations associated with existing electrolyzer technology is addressed, including the need for highly corrosive electrolytes and expensive electrocatalysts, by redefining conceptually-poor hydrogen electrocatalysts in neutral electrolytes. The impro...
A way through which the properties of metal-organic frameworks (MOFs) can be tuned is by engineering defects into the crystal structure. Given its intrinsic stability and rigidity, however, it is difficult to introduce defects into zeolitic imidazolate frameworks (ZIFs)-and ZIF-8, in particular-without compromising crystal integrity. In this work, it is shown that the acoustic radiation pressure as well as the hydrodynamic stresses arising from the oscillatory flow generated by coupling high frequency (MHz-order) hybrid surface and bulk acoustic waves into a suspension of ZIF-8 crystals in a liquid pressure transmitting medium is capable of driving permanent structural changes in their crystal lattice structure. Over time, the enhancement in the diffusive transport of guest molecules into the material's pores as a consequence is shown to lead to expansion of the pore framework, and subsequently, the creation of dangling-linker and missing-linker defects, therefore offering the possibility of tuning the type and extent of defects engineered into the MOF through the acoustic exposure time. Additionally, the practical utility of the technology is demonstrated for one-pot, simultaneous solvent-assisted ligand exchange under ambient conditions, for sub-micron-dimension ZIF-8 crystals and relatively large ligands-more specifically 2-aminobenzimidazole-without compromising the framework porosity or overall crystal structure.
MXenes hold immense potential given their superior electrical properties. The practical adoption of these promising materials is, however, severely constrained by their oxidative susceptibility, leading to significant performance deterioration and lifespan limitations. Attempts to preserve MXenes have been limited, and it has not been possible thus far to reverse the material’s performance. In this work, we show that subjecting oxidized micron or nanometer thickness dry MXene films—even those constructed from nanometer-order solution-dispersed oxidized flakes—to just one minute of 10 MHz nanoscale electromechanical vibration leads to considerable removal of its surface oxide layer, whilst preserving its structure and characteristics. Importantly, electrochemical performance is recovered close to that of their original state: the pseudocapacitance, which decreased by almost 50% due to its oxidation, reverses to approximately 98% of its original value, with good capacitance retention ( ≈ 93%) following 10,000 charge–discharge cycles at 10 A g−1. These promising results allude to the exciting possibility for rejuvenating the material for reuse, therefore offering a more economical and sustainable route that improves its potential for practical translation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.