查看更多>>摘要：Chiral conjugated microporous polymers(CCMPs)containing amide groups were designed and synthesized by Sonogashira coupling polymerization.CCMPs are reported for the first time as heterogeneous asymmetric catalyst platforms for the stabilization of Pd with applications in asymmetric catalytic synthesis.Four Pd/CCMPs heterogeneous catalysts exhibited efficient catalytic activity(of up to 87% yield)and excellent enantioselectivity(of up to 97% enantiomeric excess value)in the asymmetric Henry reaction,with a wide range of substrates and easy recovery.The Pd/CCMPs composites could be easily recycled and maintained catalytic activity after 3 cycles of reactions.A rational catalytic cycle was proposed to further understand the role of Pd/CCMPs in the Henry reaction.This study greatly extends the application of CCMPs in heterogeneous asymmetric catalysis.
查看更多>>摘要：New strategies are presented for the generation of models for linear nanopores in amorphous silica(a-SiO2)with surface structure tuned to match experimental observations.Specifically,the models successfully target not only the overall density of surface silanol groups,but also the proportion of geminal versus mono silanols for which additional experimental NMR data is reported.The latter quantity has not been appropriately described in previous modeling,and in fact has typically not been considered.Strategies include"pore drilling"of bulk a-SiO2,and"cylindrical resist"methodology forming a-SiO2 around a cylindrical exclusion region,followed by dehydroxylation and hydroxylation processes,respectively.However,these latter processes must be judiciously tailored in order to tune the proportion of geminals,in addition to the overall silanol density,to achieve experimental values.Such tailoring has not been incorporated into previous modeling.Another approach considered tunes surface structure of pores obtained by"pore drilling"through mild annealing.
查看更多>>摘要：Methane detection is important for exploring combustible ice in energy field.As the core component of the methane sensor,gas-liquid separation membranes play a crucial role in separating methane from water,which can effectively enhance the timeliness and stability of methane detection.Moreover,the correlative permeability and mechanical properties of are contradictory requirements for achieving optimum performance of membranes.Herein,a methane-water separation membrane was developed and optimized by adjusting the PEG as porogen based on PDMS and PES as functional and support layers,respectively.PDMS/PES composite membrane performed an excellent methane permeability and tensile strength.Particularly,the PEG was studied as porogen to affect the morphology and adjust pore structure of the PES layer.Considering the trade-off of methane permeability and mechanical properties,the results indicate the appropriate content of porogen is 4 wt% PEG.This work optimizes a new approach to prepare methane-water separation membrane and give a significant insight to develop methane detection for exploring new energy in seabed.
查看更多>>摘要：The collapse energy absorption behaviors of filled metal tubes were studied using silica aerogel-liquid mixture as filling material.The crushing force and energy absorption under both quasi-static and dynamic impact loads were analyzed through experiment and computer numerical simulation.On the basis that water infiltration into nanoporous materials can absorb energy,a new energy absorption material based on silica aerogels was featured for this paper.The composed aerogel-liquid systems with three solid-liquid mass ratios of 1:10,1:20 and 1:40,as well as the silica aerogel-NaCl solution with different salinity of 5%,12.5%,and 20% were experimentally studied.The pressure-volumetric strain curves of the aerogel liquid systems based on both quasi-static compression and high-speed Hopkinson Bar impact experiments were acquired,and the energy absorption densities were evaluated.Axial crushing mechanical properties of filling tubes with such nanoporous liquid systems were simulated by using validated finite element methodology,and the tube collapse stress-strain curve and buckling shapes of empty and filled tubes were compared.The results demonstrated that aerogel materials with reasonable pore diameters,or by adjusting the solid-liquid mass ratio and the electrolyte-solution ratio,the convincing crush force efficiency can be achieved which exhibits potential engineering usefulness.
查看更多>>摘要：Hybrid titania phosphonate materials can demonstrate a high added value as tailored sorption materials.They combine high chemical stability with great structural versatility,given the wide diversity of functional groups that can be incorporated.Hereto,a fundamental understanding of the synthesis strategies influencing the material performance is required.Therefore three porous TiO2 phosphonate hybrid structures with different functional groups(octyl,propyl,and phenyl)were evaluated in a solid-phase extraction application aimed towards solvent separation.The synthesis was performed by mixing bridged diphosphonic acids(DPAs)with Ti(OBu)4 in a water-ethanol mixture at 30 ℃,followed by a hydrothermal post-treatment at 120 ℃.The materials were characterized by ICP-AES,31P solid-state CP/MAS NMR,Raman and FTIR spectroscopy,X-ray diffraction,N2-sorption,and transmission electron microscopy.It is shown that the diphosphonic acids are quantitatively incorporated in the hybrid structures,leading to nanosized particles with a complex but uniquely functionalized surface.A study of the pore structure as a function of the incorporated DPA amount showed materials with a maximum BET surface area of 379 m~2/g.The alkyl functionalized hybrid titania phosphonates demonstrated excellent and tunable sorption behavior.
查看更多>>摘要：Adsorption has been proved to be an effective control method of Volatile organic compounds(VOCs).However,the design of porous carbon materials with a high VOCs adsorption performance is still a challenging topic.Herein,we proposed a novel material preparation path,namely,the synthesis of porous carbon materials guided by molecular simulation.Firstly,the optimal adsorption pore size of VOCs was calculated by grand canonical Monte Carlo(GCMC)simulation,and then cork based porous carbon with the optimal pore size controlled by urea and KOH was prepared.The sample treated at 900 ℃ had a specific surface area of 1940 m~2/g,a total pore volume of 1.27 cm~3/g,a micropore volume of 0.71 cm~3/g,which showed an excellent VOCs adsorption performance at 25 ℃.Specifically,the dynamic adsorption capacity of acetone and toluene were 6.1 mmol/g and 5.4 mmol/g,and the static adsorption capacity of acetone and toluene were 17.5 mmol/g(18 kPa)and 9.5 mmol/g(3 kPa),respectively.In terms of the pore size distribution,the contribution of the optimal pore sizes to the adsorption process was estimated to be about 69% for acetone and 59% for toluene.Besides,the relationship between the optimal pore size and its adsorption capacity was explored by mathematical methods,which showed a highly linear one.This study provides a novel idea for the design and optimization of excellent adsorbent materials.
查看更多>>摘要：Ni/CeO2-Al2O3 with bimodal porous structure and two different CeO2 concentrations(low:5 wt% and high:15 wt%)were prepared by the refluxed co-precipitation method and characterized by N2 physisorption,XRD,TPR,H2-TPD,and CO2-TPD.Catalysts were tested in combined steam and dry reforming of methane(CSDRM)at atmospheric pressure,600℃-700 ℃ and CH4:CO2:H2O = 1:0.48:0.8,in order to prepare synthesis gas with H2:CO ratio of 2:1.The catalytic activity decreases with increasing ceria content,the best catalyst being Ni/CeO2(5 wt%)-Al2O3.The good activity obtained for Ni/CeO2(5 wt%)-Al2O3 is a consequence of the more intimate contact of ceria with alumina,providing higher metal-support interaction,but also of the higher dimensions of larger pores which contribute to the better targeting of the reagents to the catalytic sites.In the used catalysts,the ceria presence better preserved the bimodal porous structure and decreased the carbon deposition by ~70%.
查看更多>>摘要：The removal of glyphosate via the adsorption process is one of the essential routes for decreasing its harmful impact.Here,we investigate the glyphosate adsorption on the Lewis acidic zeolites through density functional theory(DFT)calculations.We found that Hf-BEA provides the highest adsorption energy(-44.1 kcal/mol)as compared to ones of other zeolites.This result corresponds to its highest ordered Lewis acidity calculated by ammonia adsorption.There is a strong correlation between glyphosate and ammonia adsorption energies,as shown in a linear scaling relationship.This result implies the significant role of the Lewis acidity strength of zeolite in glyphosate adsorption process.The adsorption activity which related to zeolite pore structures(BEA,FAU,ZSM-5 and MOR)are found in the order of Hf-BEA>Hf-ZSM-5 ~ Hf-MOR>Hf-FAU.The effect of water on the glyphosate adsorption is also investigated.Water is adsorbed on Sn-BEA zeolite much weaker than glyphosate and thus the active site of zeolite cannot be blocked by it.The trend of adsorption energies remains the same as in vacuum.Finally,the hydrolysis of metal-substituted active sites to form open sites strengthens the adsorption of glyphosate.
查看更多>>摘要：Porous carbons with controlled pore structure have attracted great interest owing to their excellent applicatior potential.Herein,we report a simple synthetic route to synthesize the core-shell C@SiO2 spheres with various pore structures by calcining core-shell structured RF@SiO2(RF = resorcinol-formaldehyde resin).The obtained C@SiO2 spheres had high surface areas(238.5-732.5 m~2/g),large pore volume(0.111-0.647 cm~3/g)and abundant micro-mesoporous structure.The mesopore size of C@SiO2 spheres can be easily turned in the range oi 8-15 nm,by simply modifying the carbonization temperature,size and heating rate of RF@SiO2 spheres.Among these,S-C@SiO2-400 spheres had higher mesopore volume of 0.207 cm~3/g,this was related to internal carbon slices structure.Meantime,the toluene adsorption capacity of S-C@SiO2-400 spheres could reach 448.2 mg/g,which increased by 88.73% compared to ordinary carbon spheres.Moreover,the formation mechanism of the mesopore carbon slices structure was evaluated based on controlled experiments.This work provides a new synthetic method of micro-mesoporous carbon spheres,which can further enrich the application of carbon materials.
查看更多>>摘要：The growth process of chabazite seed crystal transformed into chabazite zeolite membrane in an organic template-free and fluoride-containing synthesis gel was investigated in details.The characterization results showed that the formation process of organic template-free chabazite zeolite membrane included the processes of seed crystal dissolution and chabazite crystal reconstruction.In the first process of seed dissolution into amorphous,the secondary building units(D6Rs)of CHA framework were completely destroyed except for the presence of a small number of 4Rs.While the amorphous contained many primary building units(TO4)as the nucleation sites in the second process of chabazite crystal reconstruction,which nucleated rapidly again under the promotion of fluorine anion.With the further prolongation of crystallization time,the regenerated secondary structural units connected together to reconstruct the framework structure of chabazite zeolite,and gradually grew into a continuous and dense membrane layer with the cross-linking growth of chabazite zeolite.In addition,chabazite zeolite membrane exhibited high permeation flux and excellent long-term hydrothermal stability for the separation of water-rich mixtures.For 50 wt% EtOH/H2O and 50 wt% IPA/H2O binary mixtures at 348 K,the stable permeation fluxes of the membranes were as high as 13.50 kg m~(-2)h~(-1)and 14.80 kg m~(-2)h~(-1),respectively.
NSTL