Chiral BINAP-based hierarchical porous polymers as platforms for efficient heterogeneous asymmetric catalysis

Two vinyl‐functionalized chiral2,2'‐bis(diphenylphosphino)‐1,1'‐binaphthyl(BINAP)ligands,(S)‐4,4'‐divinyl‐BINAP and(S)‐5,5'‐divinyl‐BINAP,were successfully synthesized.Chiral BINAP‐based porous organic polymers(POPs),denoted as4‐BINAP@POPs and5‐BINAP@POPs,were efficiently prepared via the copolymerization of vinyl‐functionalized BINAP with divinyl benzene under solvothermal conditions.Thorough characterization using nuclear magnetic resonance spectroscopy,thermogravimetric analysis,extended X‐ray absorption fine structure analysis,and high‐angle annular dark‐field scanning transmission electron microscopy,we confirmed that chiral BINAP groups were successfully incorporated into the structure of the materials considered to contain hierarchical pores.Ru was introduced as a catalytic species into the POPs using different synthetic routes.Systematic investigation of the resultant chiral Ru/POP catalysts for heterogeneous asymmetric hydrogenation ofβ‐keto esters revealed their excellent chiral inducibility as well as high activity and stability.Our work thereby paves a path towards the use of advanced hierarchical porous polymers as solid chiral platforms for heterogeneous asymmetric catalysis.

Preparation and properties of a low-cost porous ceramic support from low-grade palygorskite clay and silicon-carbide with vanadium pentoxide additives

Alow-cost porous ceramic support was prepared from low-grade palygorskite clay(LPGS) and silicon carbide(SiC)with vanadium pentoxide(V_(2) O_(5)) additives by a dry-press forming method and sintering.The effects of SiC-LPGS ratio,pressing pressure,carbon powder pore-forming agent and V_(2) O_(5) sintering additives on the microstructure and performance of the supports were investigated.The addition of an appropriate amount of SiC to the LPGS can prevent excessive shrinkage of the support during sintering,and increase the mechanical strength and open porosity of the supports.The presence of SiC(34.4%) led to increases in the open porosity and mechanical strength of 40.43% ± 0.21% and(17.76 ± 0.51) MPa,respectively,after sintering at 700℃ for 3 h.Because of its low melting point,V_(2) O_(5) can melt to liquid during sintering,which increases the mechanical strength of the supports and retains the porosity.Certainly,this can also encourage efficient use of the LPGS and avoid wasting resources.

Fabrication of ridged microstructures on FeCrAl porous metal support enhanced catalyst coating performance by UV-laser micromilling

The enhancement of catalyst coating performance is significantly influenced by the microstructures on the surface of catalyst supports.This study explores the fabrication of ridged microstructures on the surface of the FeCrAl porous metal,which serves as electrified catalyst support for methanol steam reforming(MSR),using ultraviolet(UV)-laser micromilling technology.The formation mechanism of these ridged microstructures was thoroughly analyzed.Surface morphology under different laser processing parameters was examined using scanning electron microscopy(SEM).Surface oxygen context and roughness were measured with energy-dispersive X-ray spectroscopy and a 3D laser confocal microscope,respectively.Contact angles of the microstructures under different laser conditions were observed using a contact angle measuring instrument.After laser processing,the porous metal supports were loaded with catalysts,and the performance of these catalyst coatings was tested using ultrasonic vibration tests.SEM observations highlighted improved uniformity of the catalyst coating on the support after laser processing.Experimental results showed that supports processed with UV lasers exhibited better hydrophilicity,with contact angles mostly less than 90°,facilitating better diffusion and adhesion of the catalyst solution.Optimal catalyst coating performance on FeCrAl porous metal support with ridge microstructure surface was achieved with laser processing parameters set at200 mm/s speed,40 kHz frequency,and 5 scans.The optimal microstructure surface demonstrated a load mass of approximately0.5 g and a catalyst coating strength of 87.72%.This represents approximately 17 times and 10 times the performance of unprocessed surfaces,respectively,after 8 min of ultrasonic vibration.

Effects of Porous Alumina Support and Plating Time on Electroless Plating of Palladium Membrane

The present work was focused on the preparation of palladium alloy membranes and the effect of properties of ceramic support on the composited membrane morphology. Palladium-base membrane is known to have high selectivity and stability for hydrogen separation. In order to increase hydrogen permeation and separation factor, the membrane must be thinner and defect-free. Palladium membrane supported on a porous alumina prepared by electroless plating is the promising method to provide good hydrogen permeability. The alumina tube substrate was pre-seeded by immersing in the palladium acetate solution and followed by reduction in the alkaline hydrazine solution. After that, the deposition of palladium membrane could be achieved from the plating bath containing ethylenediamine tetraacetic acid （EDTA） stabilized palladium complex and hydrazine. The morphology of palladium film was observed to progress as a function of plating time and a dense layer membrane was available after plating for 3 h. The porosity of ceramic support exhibited an effect on the microstructure of deposited film such that the support with low porosity tended to achieve a defect free palladium membrane.

New solid superbases: potassium nitrate supported on porous materials

ACCORDING to Tanabe’s definition, all materials possessing the basic strength （H-） over 26.5 are superbases. However, most of superbases known up to now, including CaO and SrO evacuated at 1173 K, K or Na metal supported on KOH/γ-Al2O3, etc. are extremely sensitive to CO2 or H2O in the atmosphere, which limits their application in industrial scale. In or-

Improved hydrogen separation performance of asymmetric oxygen transport membranes by grooving in the porous support layer

Hydrogen separation through oxygen transport membranes(OTMs)has attracted much attention.Asymmetric membranes with thin dense layers provide low bulk diffusion resistances and high overall hydrogen separation performances.However,the resistance in the porous support layer(PSL)limits the overall separation performance significantly.Engineering the structure of the PSL is an appropriate way to enable fast gas transport and increase the separation performance.There is no relevant research on studying the influence of the PSL on hydrogen separation performance so far.Herein,we prepared Ce0.85Sm0.15O1.925–Sm0.6Sr0.4Cr0.3Fe0.7O3-δ(SDC-SSCF)asymmetric membranes with straight grooves in PSL by tape-casting and laser grooving.A~30%improvement in the hydrogen separation rate was achieved by grooving in the PSLs.It indicates that the grooves may reduce the concentration polarization resistance in PSL for the hydrogen separation process.This work provides a straight evidence on optimizing the structures of PSL for improving the hydrogen separation performance of the membrane reactors.

Shedding light on the reversible deactivation of carbon-supported single-atom catalysts in hydrogenation reaction

Carbon-supported single-atom catalysts were found to suffer reversible deactivation in catalytic hydrogenation,but the mechanism is still unclear.Herein,nitro compounds hydrogenation catalyzed by N-doped carbon-supported Co single atom(Co1/NC)was taken as a model to uncover the mechanism of the reversible deactivation phenomenon.Co1/NC exhibited moderate adsorption towards the substrate molecules(i.e.,nitro compounds or related intermediates),which could be strengthened by the confinement effect from the porous structure.Consequently,substrate molecules tend to accumulate within the pore channel,especially micropores that host Co1,making it difficult for the reactants to access the active sites and finally leading to their deactivation.The situation could be even worse when the substrate molecules possess a large size.Nevertheless,the catalytic activity of Co1/NC could be restored via a simple thermal treatment,which could remove the adsorbates within the pore channel,hence releasing active sites that were originally inaccessible to reactants.