Three-dimensional porous scaffolds doped with the heteroatoms show excellent performances in energy conversion and storage. Herein, we report a green synthesis approach to construct the oxygen-doped ...porous carbon electrodes by carbonizing the oxygen-rich biomass material, sodium alginate. By precisely controlling the carbonization temperature and increasing the mole ratio of α-L-guluronic acid units/β-D-mannuronic acid units in sodium alginate, the morphology, oxygen content and electrical conductivity of the as-obtained carbonaceous electrode are well balanced. This electrode material delivers capacitance of up to 424.6 F g−1 in 6 M potassium hydroxide (KOH) electrolyte at 1 A g−1, and good cyclic stability with the capacitance retention of >90% after 20,000 charge-discharge cycles. Such excellent electrochemical performance can be attributed to both the unique hierarchical macro-/meso-/microporous structure and the presence of abundant oxygen-containing functional groups in the as-prepared carbonized sodium alginate aerogels. The capacitance of our oxygen-doped porous carbon electrodes is at least twice greater than those of other carbonaceous electrodes produced from biomass precursors reported in literatures. This work provides a facile, effective and environmental-friendly approach for the fabrication of high-performance heteroatom-doped carbon-based electrodes for supercapacitor applications.
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•Oxygen-doped porous carbon was derived from cost-effective biomass material, sodium alginate.•The carbonized aerogel shows 3D interconnected structure with large surface area.•Carbonization temperature and G/M ratio are controlled to adjust the electrochemical properties.•The obtained carbon shows excellent specific capacitance (426.6F/g at 1A/g) and cycling stability.•The results pave a road for the future implication in cost-effective and eco-friendly energy storage devices.
The effect of polyethylene glycol (PEG) additive on the synthesis of TS-1 zeolites was investigated by changing the addition amount of PEG and the crystallization time. Adding suitable amount of PEG ...may effectively inhibit the generation of unfavorable anatase, and result in the formation of TS-1 zeolites enriched tetrahedral framework Ti species with a short crystallization time (1.5 days). The resultant TS-1 zeolites showed significant improvement in catalyzing epoxidation of 1-hexene with H
2
O
2
as oxidant. A turnover frequency (TOF) up to 161 h
−1
could be obtained over the anatase-free TS-1 zeolite, much higher than the conventional TS-1 zeolite (TOF: 95 h
−1
). This work demonstrated that using a small amount of PEG additive could be beneficial for the formation of anatase-free TS-1 zeolites, which may have great potential for the catalytic application in H
2
O
2
-mediated olefin epoxidation.
A series of amine-modified ZrSBA-15 supported PdAu bimetallic nanoparticle (NP) catalysts were prepared, and their catalytic properties were studied for the dehydrogenation of formic acid in aqueous ...solution without any additives. The catalytic activities of the supported PdAu catalysts varied with the change of amines and Pd/Au ratios. The optimized catalyst achieves a very high efficiency under ambient conditions, and even works well at a temperature near the freezing point of the solution. During the preparation process of the catalysts, different organic amines could coordinate with the cations of Au and Pd to produce metal complexes with different structure stabilities and redox properties, and finally result in the formation of PdAu NPs with different particle sizes and dispersion states. The co-existence of small PdAu alloy NPs and the suitable amino groups within the single solid support could provide highly efficient bifunctional sites for synergistically activating FA molecules to produce H 2 and CO 2 .
A series of carbon supported iron nanoparticle composites were prepared by pyrolysis of two kinds of Fe-MOF materials, Fe-diamine-dicarboxylic acid and Fe-dicarboxylic acid, and were characterized by ...a variety of characterization techniques. The composites pyrolyzed at higher temperatures are composed of iron-based nanoparticles (Fe
3
C) and porous carbon architectures with graphitic characteristics. The catalytic properties of these composites were investigated for the Friedel-Crafts acylation of aromatic compounds with acyl chlorides. Among them, Fe@NC-800, derived from the pyrolysis of Fe-diamine-dicarboxylic acid at 800 °C, exhibited excellent catalytic activity and stability for the acylation reactions, and could be easily recycled several times without an obvious loss in activity. The excellent catalytic performance of Fe@NC-800 should be mainly attributed to the microstructural characteristics of the active sites, in which most of the small iron-based nanoparticles are encapsulated in the graphitic layer of the carbon architecture, thus providing a suitable geometric environment for stabilizing iron species. Besides, the electronic effects exerted by the graphitic layer of porous carbon may also play a positive role in improving the catalytic activity and stability of the carbon supported iron-based catalyst for Friedel-Crafts acylation reactions.
Carbon supported iron nanoparticles were prepared by pyrolyzing Fe-MOF material of Fe-diamine-dicarboxylic acid, and showed excellent catalytic activity and stability for the Friedel-Crafts acylation of aromatic compounds with acyl chloride.
The encapsulation of polyoxomolybdic cobalt (CoPMA) and polyoxomolybdic acid (PMA) within the Zr-based metal–organic frameworks (Zr-MOFs) of UiO-bpy (connected by 2,2′-bipyridine-5,5′-dicarboxylic ...acid linkers) and UiO-67 (connected by 4,4′-biphenyldicarboxylic acid linkers) has been achieved by direct solvothermal synthesis. Relatively high content of polyoxometalate (POM) clusters (ranging from 12 to 15 wt % loading) could be introduced to the cages of Zr-MOFs to form uniform hybrid composites of POM@Zr-MOFs. The catalytic properties of these composites were investigated for the olefins epoxidation with H2O2 or molecular O2 as oxidant. Among them, the catalyst CoPMA@UiO-bpy showed the highest catalytic activity and stability for cyclooctene epoxidation with H2O2 as oxidant and could also act as efficient heterogeneous catalyst for the oxidation of styrene and 1-octene with O2 as oxidant and tert-butyl hydroperoxide (t-BuOOH) as initiator. The excellent catalytic performance of the hybrid composite CoPMA@UiO-bpy should be mainly attributed to the uniform distribution of POM clusters within the size-matched cages of Zr-MOFs, as well as the multiple interactions between the CoPMA clusters and the functional groups (bipyridine and Zr–OH) located in the framework of UiO-bpy.
Developing an effective strategy to synthesize perfect titanosilicate TS-1 zeolite crystals with desirable morphologies, enriched isolated framework Ti species, and thus enhanced catalytic oxidation ...properties is a pervasive challenge in zeolite crystal engineering. We here used an amino acid l-carnitine as a crystal growth modifier and ethanol as a cosolvent to regulate the morphologies and the Ti coordination states of TS-1 zeolites. During the hydrothermal crystallization process, the introduced l-carnitine can not only tailor the anisotropic growth rates of zeolite crystals but also induce the formation of uniformly distributed framework Ti species through building a suitable chemical interaction with the Ti precursor species. Condition optimizations could afford the generation of perfect hexagonal plate TS-1 crystals and elongated platelet TS-1 crystals enriched in tetrahedral framework Ti sites (TiO4) or mononuclear octahedrally coordinated Ti species (TiO6). Both samples showed significant improvement in catalytic activity for the H2O2-mediated epoxidation of alkenes. In particular, the elongated platelet TS-1 enriched in “TiO6” species afforded the highest activity in 1-hexene epoxidation, with a turnover frequency (TOF) of up to 131 h–1, which is approximately twice as high as that of the conventional TS-1 zeolite (TOF: 65 h–1) and even higher than those of the literature-reported TiO6-containting TS-1 catalysts derived from the hydrothermal post-treatment of TS-1 zeolites. This work demonstrates that the morphologies and the titanium coordination states of TS-1 zeolites can be effectively tuned by directly introducing suitable crystal growth modifiers, thus providing new opportunities for developing highly efficient titanosilicate zeolite catalysts for important catalytic applications.
Hybrid composites of phosphomolybdic acid@UiO-66 (PMo12@UiO-66) and Co-substituted phosphomolybdic acid@UiO-66 (PMo11Co@UiO-66) were synthesized using the direct solvothermal method. A variety of ...characterization results demonstrated that phosphomolybdic acid (PMo12) or Co-substituted phosphomolybdate acid (PMo11Co) clusters are uniformly dispersed in the cages of Zr-based metal-organic UiO-66 frameworks. The catalytic properties of these hybrid composites were investigated by applying the epoxidation of olefins with tert-butyl hydroperoxide as the oxidant. Compared to PMo12@UiO-66, PMo11Co@UiO-66 showed a much higher catalytic activity and was simply recovered by filtration and reused for at least ten runs without significant loss of catalytic activity. Particularly, PMo11Co@UiO-66 can efficiently convert cyclic olefins like limonenes to epoxides, and its selectivity to 1,2-limonene oxide reached 91% in the presence of a radical inhibitor such as hydroquinone. The excellent catalytic activity and stability of the hybrid composite PMo11Co@UiO-66 are mainly attributed to the uniform distribution of highly active PMo11Co units within the smaller cages of UiO-66, to the suitable surface polarity of the hybrid composite for facilitating the access of reagents and solvent, and to the strong interface-interactions between the polyoxometalate and the UiO-66 framework.
Hybrid composites based on Co-substituted phosphomolybdic acid (PMo11Co) and UiO-66 were synthesized by the direct solvothermal method. PMo11Co@UiO-66 showed high catalytic activity and stability for the epoxidation of a variety of olefins with t-BuOOH as the oxidant.
The chemical microenvironment of polyoxometalates (POMs) encapsulated in metal-organic frameworks (MOFs) presents a significant influence on their catalytic performance, which can be easily regulated ...by the linker functional group alteration or metal substitution in MOFs. Herein, a series of cesium phosphomolybdate (CsPM) encapsulated in hierarchical porous UiO-66-X composites (CsPM@HP-UiO-66-X, X = H, 2CH
3
, or 2OH, where X represents the alterable group grafted onto the linker benzene ring) were successfully synthesized through a one pot modulated solvothermal method. The catalytic performances of the obtained materials were explored in alkene epoxidation reaction with
tert
-butyl hydroperoxide (
t
-BuOOH). CsPM@HP-UiO-66-2CH
3
showed relatively high catalytic activity, stability, and epoxidation selectivity in cyclooctene epoxidation among the CsPM@HP-UiO-66-X composites. Moreover, CsPM@HP-UiO-66-2CH
3
was effective in the epoxidation of numerous alkenes, especially cyclic alkenes. The superior catalytic activity of CsPM@HP-UiO-66-2CH
3
is mainly attributed to the modulation of the microenvironment surrounding CsPM active sites by introducing a hydrophobic methyl group. Meanwhile, the size-matched effect, the introduction of cesium cations, and the strong metal-support interactions (SMSIs) between CsPM and HP-UiO-66-2CH
3
play a crucial role in the stability of CsPM@HP-UiO-66-2CH
3
.
CsPM@HP-UiO-66-2CH
3
showed preferable catalytic performance in alkene epoxidation reaction among CsPM@HP-UiO-66-X composites, which is mainly attributed to the modulation of the microenvironment surrounding CsPM active sites with a methyl group.
The hybrid composite of cesium phosphomolybdate (CsPM) encapsulated in hierarchical porous UiO-66 (HP-UiO-66) was synthesized using a modulated solvothermal method. A variety of characterization ...results demonstrated that the pore size distribution of CsPM@HP-UiO-66 is broader than traditional microporous CsPM@UiO-66 and cesium phosphomolybdate clusters are uniformly distributed in the octahedral cages of HP-UiO-66. The catalytic properties of the hybrid composite were investigated in alkene epoxidation reaction with
tert
-butyl hydroperoxide (
t
-BuOOH) as an oxidant. CsPM@HP-UiO-66 showed much higher catalytic activity for the alkene epoxidation reaction in comparison with the reference catalysts and could be easily reused by centrifugation and recycled for at least ten runs without significant loss in catalytic activity. The superior catalytic activity and stability of the hybrid composite CsPM@HP-UiO-66 should be mainly attributed to the hierarchical pores in the support HP-UiO-66 promoting the diffusion of alkene molecules, the uniform distribution of highly active CsPM clusters in the octahedral cages of HP-UiO-66, the introduction of cesium cations to form the insoluble cesium phosphomolybdate and the strong metal-support interactions (SMSI) between the CsPM clusters and the HP-UiO-66 framework.
Cesium phosphomolybdate encapsulated in HP-UiO-66 was successfully synthesized. The obtained materials showed superior catalytic performance in alkene epoxidation reaction, which was attributed to the well-designed CsPM@HP-UiO-66 composites.
Two hybrid compounds, namely Cu(3atrz)
PMoMo
O
(1) and Cu(3atrz)
PMo
O
(2), were synthesized through hydrothermal reactions of 3-amino-1,2,4-triazole (3atrz), phosphomolybdic acid (PMA) and ...appropriate copper salts. Crystal structure analysis reveals that compound 1 contains one-dimensional Cu-3atrz chains. The unit of compound 2 contains a double calyx3arene-shaped hexamer, which is composed of six two-coordinated Cu
atoms and six 3atrz ligands. Both compounds 1 and 2 present a three-dimensional hybrid structure, which is built by the self-assembly of Cu-3atrz clusters and Keggin-type PMA units. The resulting hybrid compounds can act as highly efficient heterogeneous catalysts for the selective oxidation of olefins with molecular oxygen as the oxidant in the presence of a trace amount of tert-butyl hydroperoxide (t-BuOOH). Their excellent catalytic properties can be mainly attributed to the existence of stabilized Cu
complexes with an appropriate chemical environment and a spacious structure, which can interact with t-BuOOH to form catalytic sites for the direct activation of O
. This work demonstrates that the hybrid compounds assembled from copper-3atrz complexes and phosphomolybdic acid may have great potential in molecular O
-mediated catalytic oxidation reactions, which can certainly build a platform for deep insight into the biologically relevant catalytic oxidation processes.
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