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1.
The synthesis of hierarchically mesoporous polymers with multiple functionalities is challenging. Herein we reported a template‐free strategy for synthesis of phenolic azo‐polymers with hierarchical porous structures based on diazo‐coupling reaction in aqueous solution under mild conditions. The resultant polymers have surface areas up to 593 m2 g?1 with the mesopore ratio of >80 %, and a good ability to complex with metal ions, such as Cu2+, Zn2+,Ni2+, achieving a metal loading up to 26.24 wt %. Moreover, the polymers complexed with Zn showed excellent performance for catalyzing the reaction of CO2 with epoxide, affording a TOF of 2570 h?1 in the presence of tetrabutyl ammonium bromide (7.2 mol %). The polymer complexed with Cu could catalyze the oxidation of alcohol with high efficiency.  相似文献   

2.
Three porous organic polymers (POPs) containing H, COOMe, and COO? groups at 2,6‐bis(1,2,3‐triazol‐4‐yl)pyridyl (BTP) units (i.e., POP‐1, POP‐2, and POP‐3, respectively) were prepared for the immobilization of metal nanoparticles (NPs). The ultrafine palladium NPs are uniformly encapsulated in the interior pores of POP‐1, whereas uniform‐ and dual‐distributed palladium NPs are located on the external surface of POP‐2 and POP‐3, respectively. The presence of carboxylate groups not only endows POP‐3 an outstanding dispersibility in H2O/EtOH, but also enables the palladium NPs at the surface to show the highest catalytic activity, stability, and recyclability in dehalogenation reactions of chlorobenzene at 25 °C. The palladium NPs on the external surface are effectively stabilized by the functionalized POPs containing BTP units and carboxylate groups, which provides a new insight for highly efficient catalytic systems based on surface metal NPs of porous materials.  相似文献   

3.
Stable chromium, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, and iridium metal nanoparticles (M‐NPs) have been reproducibly obtained by facile, rapid (3 min), and energy‐saving 10 W microwave irradiation (MWI) under an argon atmosphere from their metal–carbonyl precursors [Mx(CO)y] in the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm][BF4]). This MWI synthesis is compared to UV‐photolytic (1000 W, 15 min) or conventional thermal decomposition (180–250 °C, 6–12 h) of [Mx(CO)y] in ILs. The MWI‐obtained nanoparticles have a very small (<5 nm) and uniform size and are prepared without any additional stabilizers or capping molecules as long‐term stable M‐NP/IL dispersions (characterization by transmission electron microscopy (TEM), transmission electron diffraction (TED), and dynamic light scattering (DLS)). The ruthenium, rhodium, or iridium nanoparticle/IL dispersions are highly active and easily recyclable catalysts for the biphasic liquid–liquid hydrogenation of cyclohexene to cyclohexane with activities of up to 522 (mol product) (mol Ru)?1 h?1 and 884 (mol product) (mol Rh)?1 h?1 and give almost quantitative conversion within 2 h at 10 bar H2 and 90 °C. Catalyst poisoning experiments with CS2 (0.05 equiv per Ru) suggest a heterogeneous surface catalysis of Ru‐NPs.  相似文献   

4.
Crystalline and porous covalent organic frameworks (COFs) and metal‐organic frameworks (MOFs) materials have attracted enormous attention in the field of photocatalytic H2 evolution due to their long‐range order structures, large surface areas, outstanding visible light absorbance, and tunable band gaps. In this work, we successfully integrated two‐dimensional (2D) COF with stable MOF. By covalently anchoring NH2‐UiO‐66 onto the surface of TpPa‐1‐COF, a new type of MOF/COF hybrid materials with high surface area, porous framework, and high crystallinity was synthesized. The resulting hierarchical porous hybrid materials show efficient photocatalytic H2 evolution under visible light irradiation. Especially, NH2‐UiO‐66/TpPa‐1‐COF (4:6) exhibits the maximum photocatalytic H2 evolution rate of 23.41 mmol g?1 h?1 (with the TOF of 402.36 h?1), which is approximately 20 times higher than that of the parent TpPa‐1‐COF and the best performance photocatalyst for H2 evolution among various MOF‐ and COF‐based photocatalysts.  相似文献   

5.
BaCeO3‐a and BaCeO3‐b, with strong basic sites, were synthesized by using a co‐precipitation method at different calcination temperatures, and used as supports to evaluate their performance in ammonia synthesis. The ammonia synthesis rate with the 1.25 % Ru/BaCeO3‐a catalyst is 24 mmol g?1 h?1, which is higher than that of 1.25 % Ru/BaCeO3‐b catalyst (18 mmol g?1 h?1) at 3 MPa and 450 °C. Moreover, the performance of the 4 % Cs‐1.25 % Ru/BaCeO3‐a catalyst was further improved to 28 mmol g?1 h?1, and no sign of deactivation was observed after a reaction time of 120 h. The XPS and H2 temperature‐programmed reduction analyses indicated that the Ru/BaCeO3‐a catalyst has more oxygen vacancies than the Ru/BaCeO3‐b catalyst. In addition, the average Ru particle size of the Ru/BaCeO3‐a catalyst is closer to 2 nm than the Ru/BaCeO3‐b catalyst, which promotes the generation of B5‐type sites (the active site for N2 dissociation). The CO2 temperature‐programmed desorption analysis indicates that BaCeO3‐a has a high basic density, which is beneficial for electron transfer to Ru and further facilitates the dissociation of N≡N bonds.  相似文献   

6.
We have synthesized a porous Mo‐based composite obtained from a polyoxometalate‐based metal–organic framework and graphene oxide (POMOFs/GO) using a simple one‐pot method. The MoO2@PC‐RGO hybrid material derived from the POMOFs/GO composite is prepared at a relatively low carbonization temperature, which presents a superior activity for the hydrogen‐evolution reaction (HER) in acidic media owing to the synergistic effects among highly dispersive MoO2 particles, phosphorus‐doped porous carbon, and RGO substrates. MoO2@PC‐RGO exhibits a very positive onset potential close to that of 20 % Pt/C, low Tafel slope of 41 mV dec?1, high exchange current density of 4.8×10?4 A cm?2, and remarkable long‐term cycle stability. It is one of the best high‐performance catalysts among the reported nonprecious metal catalysts for HER to date.  相似文献   

7.
Different kinds of porous organic polymers (POPs) bearing 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BDP) fluorophores have been developed to generate singlet oxygen upon light illumination. Herein, four imine‐linked POPs were prepared by copolymerization of amine and aldehyde with different ratios of di‐aldehyde A1 and A2. The POPs were investigated by a combination of techniques such as solid 13C NMR, FTIR, and nitrogen absorption–desorption isotherms and electronic microscopy. The results demonstrated that these POPs were prone to form hierarchical porous architectures. Scanning electron microscopy and transmission electron microscopy images revealed that the spherical morphologies showed different roughness, that is, BDP‐POPs with more BDP aldehyde A2 presented rougher surface. Finally, these POPs were used to generate singlet oxygen (1O2) monitored by 1,3‐diphenylisobenzofuran and bioimaging in HeLa cells. Our results indicated that the ability to generate 1O2 is dependent on the amount of BDP. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 319–327  相似文献   

8.
Phosphorus‐rich metal phosphides have very high lithium storage capacities, but they are difficult to prepare. A low‐temperature phosphorization method based on Mg reducing PCl3 in ZnCl2 molten salt at 300 °C is developed to synthesize phosphorus‐rich CuP2@C from a Cu‐MOF derived Cu@C composite. Abnormal oxidation of Cu by Zn2+ in the molten salt is observed, which leads to the porous honeycomb nanostructure and homogeneously distributed ultrafine CuP2 nanocrystals. The honeycomb CuP2@C exhibits excellent lithium storage performance with high reversible capacity (1146 mAh g?1 at 0.2 A g?1) and superior cycling stability (720 mAh g?1 after 600 cycles at 1.0 A g?1), showing the promising application of P‐rich metal phosphides in lithium ion batteries.  相似文献   

9.
Visible‐light‐driven photoreduction of CO2 to energy‐rich chemicals in the presence of H2O without any sacrifice reagent is of significance, but challenging. Herein, Eosin Y‐functionalized porous polymers (PEosinY‐N, N=1–3), with high surface areas up to 610 m2 g?1, are reported. They exhibit high activity for the photocatalytic reduction of CO2 to CO in the presence of gaseous H2O, without any photosensitizer or sacrifice reagent, and under visible‐light irradiation. Especially, PEosinY‐1 derived from coupling of Eosin Y with 1,4‐diethynylbenzene shows the best performance for the CO2 photoreduction, affording CO as the sole carbonaceous product with a production rate of 33 μmol g?1 h?1 and a selectivity of 92 %. This work provides new insight for designing and fabricating photocatalytically active polymers with high efficiency for solar‐energy conversion.  相似文献   

10.
Semiconductive property of elementary substance is an interesting and attractive phenomenon. We obtain a breakthrough that fibrous phase red phosphorus, a recent discovered modification of red phosphorus by Ruck et al., can work as a semiconductor photocatalyst for visible‐light‐driven hydrogen (H2) evolution. Small sized fibrous phosphorus is obtained by 1) loading it on photoinactive SiO2 fibers or by 2) smashing it ultrasonically. They display the steady hydrogen evolution rates of 633 μmol h?1 g?1 and 684 μmol h?1 g?1, respectively. These values are much higher than previous amorphous P (0.6 μmol h?1 g?1) and Hittorf P (1.6 μmol h?1 g?1). Moreover, they are the highest records in the family of elemental photocatalysts to date. This discovery is helpful for further understanding the semiconductive property of elementary substance. It is also favorable for the development of elemental photocatalysts.  相似文献   

11.
Porous organic polymers (POPs) with high porosity and tunable functionalities have been widely studied for use in gas separation, catalysis, energy conversion and energy storage. However, the high cost of organic monomers, and the use of toxic solvents and high temperatures during synthesis pose obstacles for large-scale production. Herein, we report the synthesis of imine and aminal-linked POPs using inexpensive diamine and dialdehyde monomers in green solvents. Theoretical calculations and control experiments show that using meta-diamines is crucial for forming aminal linkages and branching porous networks from [2+2] polycondensation reactions. The method demonstrates good generality in that 6 POPs were successfully synthesized from different monomers. Additionally, we scaled up the synthesis in ethanol at room temperature, resulting in the production of POPs in sub-kilogram quantities at a relatively low cost. Proof-of-concept studies demonstrate that the POPs can be used as high-performance sorbents for CO2 separation and as porous substrates for efficient heterogeneous catalysis. This method provides an environmentally friendly and cost-effective approach for large-scale synthesis of various POPs.  相似文献   

12.
Amorphous phosphorus nitride imide nanotubes (HPN) are reported as a novel substrate to stabilize materials containing single‐metal sites. Abundant dangling unsaturated P vacancies play a role in stabilization. Ruthenium single atoms (SAs) are successfully anchored by strong coordination interactions between the d orbitals of Ru and the lone pair electrons of N located in the HPN matrix. The atomic dispersion of Ru atoms can be distinguished by X‐ray absorption fine structure measurements and spherical aberration correction electron microscopy. Importantly, Ru SAs@PN is an excellent electrocatalyst for the hydrogen evolution reaction (HER) in 0.5 m H2SO4, delivering a low overpotential of 24 mV at 10 mA cm?2 and a Tafel slope of 38 mV dec?1. The catalyst exhibits robust stability in a constant current test at a large current density of 162 mA cm?2 for more than 24 hours, and is operative for 5000 cycles in a cyclic voltammetry test. Additionally, Ru SAs@PN presents a turnover frequency (TOF) of 1.67 H2 s?1 at 25 mV, and 4.29 H2 s?1 at 50 mV, in 0.5 m H2SO4 solution, outperforming most of the reported hydrogen evolution catalysts. Density functional theory (DFT) calculations further demonstrate that the Gibbs free energy of adsorbed H* over the Ru SAs on PN is much closer to zero compared with the Ru/C and Ru SAs supported on carbon and C3N4, thus considerably facilitating the overall HER performance.  相似文献   

13.
The story of the outset and the growth of radical polyaddition of bisperfluoroisopropenyl derivatives [CF2?C(CF3)? R? C(CF3)? CF2] with several organic compounds possessing carbon–hydrogen bonds is described. The reaction afforded novel fluorinated polymers bearing such organic segments in polymer main chains as 1,4‐dioxane, diethyl ether, dimethoxyethane, 18‐crown‐6, triethylamine, glutaraldehyde, and alkanes which have never been supposed as direct starting compounds for preparation of polymers. The facile method for preparation of fluorinated hybrid polymers bearing alkylsilyl groups was developed with diethoxydimethylsilane and silsesquioxanes. Taking advantage of the high reactivity of the perfluoroisopropenyl group as a radical acceptor, self‐polyaddition and cyclopolymerization were investigated. Triethysilyl perfluoroisopropenyl ether [CF2? C(CF3)? O? Si(C2H5)3] was proved to be the most probable candidate for self‐polyaddition. Cyclopolymerization of perfluoroisopropenyl vinylacetate [CF2?C(CF3) OCO? CH2CH? CH2] was investigated to afford polymers possessing five‐membered‐ring units in main chains. The interconversion of the unstable fluorinated carbon radical and the stable hydrocarbon radical had an important role in the reaction. The radical addition reaction presented herein may be developed for preparation of a wide variety of novel fluorinated polymers and organic compounds possessing functional groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4101–4125, 2004  相似文献   

14.
A novel strategy has been adopted for the construction of a copolymer of benzene–benzylamine‐1 (BBA‐1), which is a porous organic polymer (POP) with a high BET surface area, through Friedel–Crafts alkylation of benzylamine and benzene by using formaldehyde dimethyl acetal as a cross‐linker and anhydrous FeCl3 as a promoter. Ruthenium nanoparticles (Ru NPs) were successfully distributed in the interior cavities of polymers through NaBH4, ethylene glycol, and hydrothermal reduction routes, which delivered Ru‐A, Ru‐B, and Ru‐C materials, respectively, and avoided aggregation of metal NPs. Homogeneous dispersion, the nanoconfinement effect of the polymer, and the oxidation state of Ru NPs were verified by employing TEM, energy‐dispersive X‐ray spectroscopy mapping, cross polarization magic‐angle spinning 13C NMR spectroscopy, and X‐ray photoelectron spectroscopy analytical tools. These three new Ru‐based POP materials exhibited excellent catalytic performance in the hydrogenation of nitroarenes at RT (with a reaction time of only ≈30 min), with high conversion, selectivity, stability, and recyclability for several catalytic cycles, compared with other traditional materials, such as Ru@C, Ru@SiO2, and Ru@TiO2, but no clear agglomeration or loss of catalytic activity was observed. The high catalytic performance of the ruthenium‐based POP materials is due to the synergetic effect of nanoconfinement and electron donation offered by the 3D POP network. DFT calculations showed that hydrogenation of nitrobenzene over the Ru (0001) catalyst surface through a direct reaction pathway is more favorable than that through an indirect reaction pathway.  相似文献   

15.
The metal sulfide‐carbon nanocomposite is a new class of anode material for sodium ion batteries, but its development is restricted by its relative poor rate ability and cyclic stability. Herein, we report the use of double‐helix structure of carrageenan–metal hydrogels for the synthesis of 3D metal sulfide (MxSy) nanostructure/carbon aerogels (CAs) for high‐performance sodium‐ion storage. The method is unique, and can be used to make multiple MxSy/CAs (such as FeS/CA, Co9S8/CA, Ni3S4/CA, CuS/CA, ZnS/CA, and CdS/CA) with ultra‐small nanoparticles and hierarchical porous structure by pyrolyzing the carrageenan–metal hydrogels. The as‐prepared FeS/CA exhibits a high reversible capacity and excellent cycling stability (280 mA h?1 at 0.5 A g?1 over 200 cycles) and rate performance (222 mA h?1 at 5 A g?1) when used as the anode material for sodium‐ion batteries. The work shows the value of biomass‐derived metal sulfide–carbon heterostuctures in sodium‐ion storage.  相似文献   

16.
The chemical and electrochemical properties of technetium metal were studied in 1–6 M HX and in 1 M NaX (pH 1 and 2.5), X = Cl, NO3. The chemical dissolution rates of Tc metal were higher in HNO3 than in HCl (i.e. 8.63 × 10?5 mol cm?2 h?1 in 6 M HNO3 versus 2.05 × 10?9 mol cm?2 h?1 in 6 M HCl). The electrochemical dissolution rates in HNO3 and HCl were similar and mainly depended on the electrochemical potential and the acid concentration. The optimum dissolution of Tc metal was obtained in 1 M HNO3 at 1 V/AgAgCl (1.70 × 10?3 mol cm?2 h?1). The dissolution potentials of Tc metal in nitric acid were in the range of 0.596–0.832 V/AgAgCl. Comparison of Tc behavior with Mo and Ru indicated that in HNO3, the dissolution rate followed the order: Mo > Tc > Ru, and for dissolution potential the order: E diss(Ru) > E diss(Tc) > E diss(Mo). The corrosion products of Tc metal were analyzed in HCl solution by UV–Visible spectroscopy and showed the presence of TcO4 ?. The surface of the electrode was characterized by microscopic techniques; it indicated that Tc metal preferentially corroded at the scratches formed during the polishing and no oxide layer was observed.  相似文献   

17.
Single‐ligand‐based electronically conductive porous coordination polymers/metal–organic frameworks (EC‐PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π‐conjugated EC‐MOF containing copper units with mixed trigonal ligands was developed: Cu3(HHTP)(THQ) (HHTP=2,3,6,7,10,11‐hexahydrotriphenylene, THQ=tetrahydroxy‐1,4‐quinone). The modulated conductivity (σ≈2.53×10?5 S cm?1 with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m2 g?1) of the Cu3(HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor.  相似文献   

18.
A novel metal‐doping strategy was developed for the construction of iron‐decorated microporous aromatic polymers with high small‐gas‐uptake capacities. Cost‐effective ferrocene‐functionalized microporous aromatic polymers (FMAPs) were constructed by a one‐step Friedel–Crafts reaction of ferrocene and s‐triazine monomers. The introduction of ferrocene endows the microporous polymers with a regular and homogenous dispersion of iron, which avoids the slow reunion that is usually encountered in previously reported metal‐doping procedures, permitting a strong interaction between the porous solid and guest gases. Compared to ferrocene‐free analogues, FMAP‐1, which has a moderate BET surface area, shows good gas‐adsorption capabilities for H2 (1.75 wt % at 77 K/1.0 bar), CH4 (5.5 wt % at 298 K/25.0 bar), and CO2 (16.9 wt % at 273 K/1.0 bar), as well as a remarkably high ideal adsorbed solution theory CO2/N2 selectivity (107 v/v at 273 K/(0–1.0) bar), and high isosteric heats of adsorption of H2 (16.9 kJ mol?1) and CO2 (41.6 kJ mol?1).  相似文献   

19.
A series of cationic and neutral RuII complexes of the general formula [Ru(L)(X) (tBuCN)4]+X? and [Ru(L)(X)2(tBuCN)3)], that is, [Ru(CF3SO3){NCC(CH3)3}4(IMesH2)]+[CF3SO3]? ( 1 ), [Ru(CF3SO3){NCC(CH3)3}4(IMes)]+[CF3SO3]? ( 2 ), [RuCl{NCC(CH3)3}4(IMes)]+Cl? ( 3 ), [RuCl{NCC(CH3)3}4(IMesH2)+Cl?]/[RuCl2{NCC(CH3)3}3(IMesH2)] ( 4 ), and [Ru(NCO)2{NCC(CH3)3}3(IMesH2)] ( 5 ) (IMes=1,3‐dimesitylimidazol‐2‐ylidene, IMesH2=1,3‐dimesityl‐imidazolin‐2‐ylidene) have been synthesized and used as UV‐triggered precatalysts for the ring‐opening metathesis polymerization (ROMP) of different norborn‐2‐ene‐ and cis‐cyclooctene‐based monomers. The absorption maxima of complexes 1 – 5 were in the range of 245–255 nm and thus perfectly fit the emission band of the 254 nm UV source that was used for activation. Only the cationic RuII‐complexes based on ligands capable of forming μ2‐complexes such as 1 and 2 were found to be truly photolatent in ROMP. In contrast, complexes 3 – 5 could be activated by UV light; however, they also showed a low but significant ROMP activity in the absence of UV light. As evidenced by 1H and 13C NMR spectroscopy, the structure of the polymers obtained with either 1 or 2 are similar to those found in the corresponding polymers prepared by the action of [Ru(CF3SO3)2(IMesH2)(CH‐2‐(2‐PrO)‐C6H4)], which strongly suggest the formation of Ru‐based Grubbs‐type initiators in the course of the UV‐based activation process. Precatalysts that have the IMesH2 ligand showed significantly enhanced reactivity as compared with those based on the IMes ligand, which is in accordance with reports on the superior reactivity of IMesH2‐based Grubbs‐type catalysts compared with IMes‐based systems.  相似文献   

20.
High‐energy‐density Li metal batteries suffer from a short lifespan under practical conditions, such as limited lithium, high loading cathode, and lean electrolytes, owing to the absence of appropriate solid electrolyte interphase (SEI). Herein, a sustainable SEI was designed rationally by combining fluorinated co‐solvents with sustained‐release additives for practical challenges. The intrinsic uniformity of SEI and the constant supplements of building blocks of SEI jointly afford to sustainable SEI. Specific spatial distributions and abundant heterogeneous grain boundaries of LiF, LiNxOy, and Li2O effectively regulate uniformity of Li deposition. In a Li metal battery with an ultrathin Li anode (33 μm), a high‐loading LiNi0.5Co0.2Mn0.3O2 cathode (4.4 mAh cm?2), and lean electrolytes (6.1 g Ah?1), 83 % of initial capacity retains after 150 cycles. A pouch cell (3.5 Ah) demonstrated a specific energy of 340 Wh kg?1 for 60 cycles with lean electrolytes (2.3 g Ah?1).  相似文献   

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