Bioinspired Molecular Scalpel for Two-Dimensional Metal-Organic Nanosheet: Design Strategies and Recent Progress.

Ultrathin two-dimensional (2D) metal-organic nanosheets (MONs) have attracted continued attention in the field of advanced functional materials. Their nanoscale thickness, high surface-to-volume ratio, and abundant accessible active sites, are superior advantages compared with their 3D bulk counterparts. Bioinspired molecular scalpel strategy is a promising method for the creation of 2D MONs, and may solve the current shortcomings of MONs synthesis. This review aims to provide a state-of-the-art overview of molecular scalpel strategies and share the results of current development to provide a better solution for MONs synthesis. Different types of molecular scalpel strategies have been systematically summarized. Both mechanisms, advantages and limitations of multiform molecular scalpel strategies have been discussed. Besides, the challenges to be overcome and the question to be solved are also introduced.

Small-size and well-dispersed Fe nanoparticles embedded in carbon rods for efficient oxygen reduction reaction.

The preparation of ultra-small and well-dispersed metal nanoparticles (NPs) is of great importance for promoting oxygen reduction. Here, a metal (Fe and Zn) NP (7 nm) based catalyst derived from a Zn-based metal-organic framework was obtained by a vapor adsorption strategy, demonstrating a high half-wave potential (0.868 V) and power density (196 mW cm-2).

Customized Synthesis of MOF Nanoplates via Molecular Scalpel Strategy for Efficient Oxygen Reduction in Zn-Air Batteries.

The production of metal-organic framework (MOF) nanoplates with well-defined geometric morphology is remarkable for expanding their applications. Herein, the cobalt-based MOF nanoplates with hexagonal channels from a layer-pillared MOF are accomplished, via a molecular scalpel strategy, utilizing monodentate pyridine to replace the bidentate 4,4'-bipyridine. The morphology can be modified from nanorods to nanoplates with controllable thickness tuned by the amounts of pyridine. Succeeding carbonization treatment transforms the MOF nanoplates into Co particles homogeneously encapsulated in the nitrogen-doped carbon layers. The prepared catalyst with a unique platelike morphology displays a high half-wave potential of 0.88 V in oxygen reduction reaction. When used in primary Zn-air batteries, it delivers a high peak power density of 280 mW cm-2 . This work clarifies the structure-morphology-reactivity connection of MOF nanoplates.

Interfacing MnO and FeCo alloy inside N-doped carbon hierarchical porous nanospheres derived from metal-organic framework to boost high-performance oxygen reduction for Zn-air batteries.

Efficient and strong non-precious metal catalysts are urgently needed for the oxygen reduction reaction (ORR). Here, a facile hydrothermal-pyrolysis process was implemented to engineer CoFe-MnO heterointerfaces encapsulated in N-doped carbon (CFM-NC) nanospheres with a metal-organic framework (MOF) as the precursor. Due to heterointerfaces and hierarchical porosity, CFM-NC-800 exhibited superior ORR activity (half-wave potential of 0.86 V) and durability (30 000 s). Importantly, CFM-NC-800-based Zn-air batteries (ZABs) were capable of extending the outstanding performance, with a high power density of 260 mW cm-2 and a specific capacity of 812 mA h g-1. Furthermore, the CFM-NC-800-RuO2-based ZABs showed remarkable stability (480 cycles), outperforming Pt/C-RuO2 (360 cycles). This work highlights the effects of CoFe-MnO heterointerfaces and hierarchical porosity in ORR electrocatalysis, thereby providing a new avenue for energy conversion and storage.

A stable Cd-MOF as a dual-responsive luminescent biosensor for the determination of urinary diphenyl phosphate and hippuric acid as biomarkers for human triphenyl phosphate and toluene poisoning.

Rapid and accurate determination of biomarkers of human poisoning in real urine is of great significance for the assessment of health status. Herein, a luminescent urea-functionalized metal-organic framework (MOF), {[Cd(L)0.5(bpbix)]·x(solv)}n (1) (H4L = 5,5'-(((naphthalene-1,5-diylbis(azanediyl))bis(carbonyl))bis(azanediyl))diisophthalic acid; bpbix = 4,4'-bis((1H-imidazol-1-yl)methyl)biphenyl), has been successfully synthesized, and exhibits good stability in aqueous solutions in the normal urinary pH range and real urine. Complex 1 can serve as a dual-responsive luminescent biosensor for the detection of diphenyl phosphate (DPP) and hippuric acid (HA) as biomarkers of flame retardant triphenyl phosphate and toluene poisoning, and shows the advantages of high sensitivity, rapid response, good anti-interference capability, and reversibility. More significantly, complex 1 is successfully applied to the sensitive and accurate detection of DPP and HA in real urine with satisfactory recoveries. This work presents a dual-responsive luminescent MOF-based biosensor for simple, rapid, accurate, and reversible determination of urinary DPP and HA, which has promising application potential for the diagnosis of diseases related to triphenyl phosphate and toluene poisoning.

From Hydrogen Bond to van der Waals Force: Molecular Scalpel Strategy to Exfoliate a Two-Dimensional Metal-Organic Nanosheet.

The facile exfoliation of a two-dimensional metal-organic nanosheet of {[Co(HL)(H2O)(Py)3/4]·1/2H2O·DMF}n [1-Py; H3L = 5-(1H-pyrazol-4-yl)isophthalic acid and Py = pyridine] was achieved, via a molecular scalpel strategy, by weakening intermolecular forces between adjacent layers. The resulting 1-Py/KB40 (KB = Ketjen black) shows an increased oxygen evolution reaction (OER) performance with an overpotential of 370 mV at a current density of 10 mA cm-2 and a Tafel slope of 58 mV dec-1. This work sheds light on the structure-morphology-reactivity relationship of such materials in OER.

MOF-derived CoNi,CoO,NiO@N-C bifunctional oxygen electrocatalysts for liquid and all-solid-state Zn-air batteries.

Metal-organic framework (MOF)-derived carbon composites with embedded metal alloy/metal oxides have attracted much attention due to their low-cost and excellent electrochemical reactivity. However, the drawback of this concept is the severe carbon evaporation during their synthesis, resulting in a reduction of active sites and catalytic durability. To solve this problem, this study proposes the possibility of using Ketjen black (KB) to replenish the carbon content. Impressively, MOF-derived bimetal and oxide N-doped porous carbon (CoNi-CoO-NiO@NC-800) exhibits extremely high catalytic activity with an oxygen reduction reaction (half-wave potential: 0.83 V) and oxygen evolution reaction (overpotential: 352 mV @ 10 mA cm-2) potential gap of 0.75 V due to the virtue of the hierarchically porous structure and sufficient active sites. By combining theoretical studies, a strong synergetic coupling of the CoNi dual metal is proposed in decreasing the overall reaction barriers and promoting the reversible oxygen reactions. Moreover, the assembled liquid- and all-solid-state Zn-air batteries (ZABs) with the bifunctional catalyst as the air cathode demonstrate superior discharging (223 mW cm-2 at 310 mA cm-2) and charging-discharging performance and long lifetime (450 cycles, 75 h). This work will provide guidance for the rational design of metal/carbon hybrid catalysts and cut-price reproducible energy systems.

Rh particles in N-doped porous carbon materials derived from ZIF-8 as an efficient bifunctional electrocatalyst for the ORR and HER.

Durable and efficient electrocatalysts toward the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) are crucial to the development of sustainable energy conversion. In this article, we report a highly active bifunctional electrocatalyst derived from ZIF-8 through simple heat-treatment activation. The resultant catalyst is enriched with Rh nanoparticles in the carbon matrix, showing excellent ORR performance with a half-wave potential (E 1/2) of 0.803 V in alkaline electrolytes; it is simultaneously active for catalyzing the HER with an overpotential of 89 mV to reach a current density of 10 mA cm2 in acidic electrolytes. The prepared RhNC-900 catalyst (1.47 wt% Rh) is comparable to the commercial Pt/C catalyst (20 wt% Pt) in terms of the ORR in alkaline media and might inspire new ideas for the development of fuel cells and water splitting.