Metal‐free heteroatom‐doped carbocatalysts with a high surface area are desirable for catalytic reactions. In this study, we found an efficient strategy to prepare nitrogen, phosphorus, and sulfur ...co‐doped hollow carbon shells (denote as NPS‐HCS) with a surface area of 1020 m2 g−1. Using a poly(cyclotriphosphazene‐co‐4,4′‐sulfonyldiphenol) (PZS) shell as carbon source and N, P, S‐doping source, and the ZIF‐67 core as structural template as well as extra N‐doping source, NPS‐HCS were obtained with a high surface area and superhydrophilicity. All these features render the prepared NPS‐HCS a superior metal‐free carbocatalyst for the selective oxidation of aromatic alkanes in aqueous solution. This study provides a reliable and facile route to prepare doped carbocatalysts with enhanced catalytic properties.
Highly efficient and selective: A synthetic route was developed to produce nitrogen, phosphorus, and sulfur co‐doped hollow carbon shells which were used as a metal‐free carbocatalyst. The carbocatalyst had a high surface area and showed superior activity in the selective oxidation of aromatic alkanes in aqueous solution.
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•Recent advances in the field of MOF-polymer composites are briefly reviewed.•Methods for making MOF-polymer composites are noted with their merits and demerits.•Utility of ...MOF-polymer composites in several relevant applications is reviewed.•Suggestions for future research that might help to further develop the field are discussed.
In this contribution, recent advances in the construction of MOF-polymer composites and their corresponding applications are briefly reviewed. The appearance of such architectures is becoming prominent in recent literature, due to the fact that the union of these two dissimilar components can give rise to a number of desirable properties that are not necessarily achieved by the individual components. For instance, while MOFs already boast unprecedented internal surface areas and highly tunable pore structures, they can often suffer from limited stability that results from the weak nature of the coordination bonding. However, recent work, outlined in this review, demonstrates that polymers can enhance MOF stability and even augment other important properties like electrical conductivity. Further, we discuss a number of other studies, where the addition of external polymer coatings or the insertion or grafting of polymer species inside the MOF pores can lead to noticeable performance enhancement in a variety of applications including water treatment, catalysis, small molecule adsorption/separation, small molecule/ion sensing, and bio-delivery. The hope is that this review will highlight the prominence of this newly emerging class of materials and demonstrate their potential in a variety of applications relevant to host–guest chemistry.
Metal–organic frameworks (MOFs) offer great promise in a variety of gas- and liquid-phase separations. However, the excellent performance on the lab scale hardly translates into pilot- or ...industrial-scale applications due to the microcrystalline nature of MOFs. Therefore, the structuring of MOFs into pellets or beads is a highly solicited and timely requirement. In this work, a general structuring method is developed for preparing MOF–polymer composite beads based on an easy polymerization strategy. This method adopts biocompatible, biodegradable poly(acrylic acid) (PAA) and sodium alginate monomers, which are cross-linked using Ca2+ ions. Also, the preparation procedure employs water and hence is nontoxic. Moreover, the universal method has been applied to 12 different structurally diverse MOFs and three MOF-based composites. To validate the applicability of the structuring method, beads consisting of a MOF composite, namely Fe–BTC/PDA, were subsequently employed for the extraction of Pb and Pd ions from real-world water samples. For example, we find that just 1 g of Fe–BTC/PDA beads is able to decontaminate >10 L of freshwater containing highly toxic lead (Pb) concentrations of 600 ppb while under continuous flow. Moreover, the beads offer one of the highest Pd capacities to date, 498 mg of Pd per gram of composite bead. Furthermore, large quantities of Pd, 7.8 wt %, can be readily concentrated inside the bead while under continuous flow, and this value can be readily increased with regenerative cycling.
Metal-organic frameworks are of interest in a number of host-guest applications. However, their weak coordination bonding often leads to instability in aqueous environments, particularly at extreme ...pH, and hence, is a challenging topic in the field. In this work, a two-step, post-synthetic polymerization method is used to create a series of highly hydrophobic, stable MOF composites. The MOFs are first coated with thin layers of polydopamine from free-base dopamine under a mild oxygen atmosphere, which then undergoes a Michael addition to covalently graft hydrophobic molecules to the external MOF surface. This easy, mild post-synthetic modification is shown to significantly improve the stability of a number of structurally diverse MOFs including HKUST-1 (Cu), ZIF-67 (Co), ZIF-8 (Zn), UiO-66 (Zr), Cu-TDPAT (Cu), Mg-MOF-74 (Mg) and MIL-100 (Fe) in wet, caustic (acidic and basic) environments as determined by powder X-ray diffraction and surface area measurements.
This work develops a new post-synthetic polymerization strategy to make various metal-organic frameworks more stable.
High internal surface areas, an asset that is highly sought after in material design, has brought metal–organic frameworks (MOFs) to the forefront of materials research. In fact, a major focus in the ...field is on creating innovative ways to maximize MOF surface areas. Despite this, large-pore MOFs, particularly those with mesopores, continue to face problems with pore collapse upon activation. Herein, we demonstrate an easy method to inhibit this problem via the introduction of small quantities of polymer. For several mesoporous, isostructural MOFs, known as M2(NDISA) (where M = Ni2+, Co2+, Mg2+, or Zn2+), the accessible surface areas are increased dramatically, from 5 to 50 times, as the polymer effectively pins the MOFs open. Postpolymerization, the high surface areas and crystallinity are now readily maintained after heating the materials to 150 °C under vacuum. These activation conditions, which could not previously be attained due to pore collapse, also provide accessibility to high densities of open metal coordination sites. Molecular simulations are used to provide insight into the origin of instability of the M2(NDISA) series and to propose a potential mechanism for how the polymers immobilize the linkers, improving framework stability. Last, we demonstrate that the resulting MOF–polymer composites, referred to as M2(NDISA)-PDA, offer a perfect platform for the appendage/immobilization of small nanocrystals inside rendering high-performance catalysts. After decorating one of the composites with Pd (average size: 2 nm) nanocrystals, the material shows outstanding catalytic activity for Suzuki–Miyaura cross-coupling reactions.
Abstract
Electrocatalytic reduction of carbon monoxide into fuels or chemicals with two or more carbons is very attractive due to their high energy density and economic value. Herein we demonstrate ...the synthesis of a hydrophobic Cu/Cu
2
O sheet catalyst with hydrophobic n-butylamine layer and its application in CO electroreduction. The CO reduction on this catalyst produces two or more carbon products with a Faradaic efficiency of 93.5% and partial current density of 151 mA cm
−2
at the potential of −0.70 V versus a reversible hydrogen electrode. A Faradaic efficiency of 68.8% and partial current density of 111 mA cm
−2
for ethanol were reached, which is very high in comparison to all previous reports of CO
2
/CO electroreduction with a total current density higher than 10 mA cm
−2
. The as-prepared catalyst also showed impressive stability that the activity and selectivity for two or more carbon products could remain even after 100 operating hours. This work opens a way for efficient electrocatalytic conversion of CO
2
/CO to liquid fuels.
Transition‐metal phosphides have received tremendous attention during the past few years because they are earth‐abundant, cost‐effective, and show outstanding catalytic performance in several ...electrochemically driven conversions including hydrogen evolution, oxygen evolution, and water splitting. As one member of the transition‐metal phosphides, CoxP‐based materials have been widely explored as electrocatalyts; however, their application in the traditional thermal catalysis are rarely reported. In this work, cobalt phosphide/carbon nanocubes are designed and their catalytic activity for the selective hydrogenation of nitroarenes to anilines is studied. A high surface area metal‐organic framework (MOF), ZIF‐67, is infused with red phosphorous, and then pyrolysis promotes the facile production of the phosphide‐based catalysts. The resulting composite, consisting of Co2P/CNx nanocubes, is shown to exhibit excellent catalytic performance in the selective hydrogenation of nitroarenes to anilines. To the best of our knowledge, this is the first report showing catalytic activity of a cobalt phosphide in nitroarenes hydrogenation.
A novel Co2P/CNx composite can be easily prepared using red‐phosphorous infused ZIF‐67 nanocubes as precursors. For the first time, the newly formed cobalt phosphide composite is shown to have excellent activity, selectivity, stability, and recyclability for the thermally driven hydrogenation of a variety of nitroarenes to anilines.
A double solvent method is for the first time used to synthesize a polymer composite that is constructed by a Ni-pyrazolate MOF and polydopamine (PDA). The resulting composite shows significantly ...enhanced water and CO2 adsorption properties compared to the parent MOF and the composite synthesized without the double solvent method.
Highlights
An all-wood hydrogel was synthesized via a simply Hofmeister effect without the use of any chemical cross-linking agent.
The all-wood hydrogel shows a high tensile strength of 36.5 MPa, a ...strain up to ~ 438%, and good conductivity, and can accurately distinguish diverse large or subtle human movements.
The all-wood hydrogel has good recyclable, biodegradable, and adjustable mechanical properties.
Wood-based hydrogel with a unique anisotropic structure is an attractive soft material, but the presence of rigid crystalline cellulose in natural wood makes the hydrogel less flexible. In this study, an all-wood hydrogel was constructed by cross-linking cellulose fibers, polyvinyl alcohol (PVA) chains, and lignin molecules through the Hofmeister effect. The all-wood hydrogel shows a high tensile strength of 36.5 MPa and a strain up to ~ 438% in the longitudinal direction, which is much higher than its tensile strength (~ 2.6 MPa) and strain (~ 198%) in the radial direction, respectively. The high mechanical strength of all-wood hydrogels is mainly attributed to the strong hydrogen bonding, physical entanglement, and van der Waals forces between lignin molecules, cellulose nanofibers, and PVA chains. Thanks to its excellent flexibility, good conductivity, and sensitivity, the all-wood hydrogel can accurately distinguish diverse macroscale or subtle human movements, including finger flexion, pulse, and swallowing behavior. In particular, when “An Qi” was called four times within 15 s, two variations of the pronunciation could be identified. With recyclable, biodegradable, and adjustable mechanical properties, the all-wood hydrogel is a multifunctional soft material with promising applications, such as human motion monitoring, tissue engineering, and robotics materials.
A new type lead-free catalyst of a Pd-Cu2O nanocomposite was developed for highly selective semi-hydrogenation of alkynes. With unprecedented selectivity for the semi-hydrogenation of terminal ...alkynes to alkenes, we show for the first time that the catalyst only hydrogenated the terminal alkynes, i.e. did not hydrogenate the internal alkynes.
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