Sulfonic groups functionalized Zr-metal organic framework for highly catalytic transfer hydrogenation of furfural to furfuryl alcohol

The highly selective catalytic transfer hydrogenation(CTH)of furfural(FF)to furfuryl alcohol(FOL)is a significant route of biomass valorization.Herein,a series microporous Zr-metal organic framework(ZrMOF)functionalized by sulfonic groups are prepared.Based on the comprehensive structural characterizations by means of X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),N2 physisorption,Thermogravimetric(TG)and Fourier transformed infrared spectroscopy(FTIR),we find that sulfonic acid(–SO_(3)H)functional groups are tethered on the UIO-66 without affecting the structure of the framework.Systematic characterizations(NH_(3)-TPD,CO_(2)-TPD,and in-situ FTIR)demonstrate that modifying of sulfonic groups on UIO-66 results in the formation of stronger Lewis acidic-basic and Brnsted acidis sites.The cooperative role of the versatile Lewis acidic-basic and Brnsted acidic sites in 60%mol fraction of sulfonic acid-containing UIO-66(UIO-S_(0.6))retain high surface area and exhibit excellent catalytic performance of 94.7%FOL yield and 16.9 h^(-1).turnover number(TOF)under mild conditions.Kinetic experiments reveal that the activation energy of the CTH of furfural(FF)over UIO-S_(0.6) catalyst is as low as 50.8 k J mol^(-1).Besides,the hydrogen transfer mechanism is investigated through isotope labeling experiments,exhibiting that theβ-H in isopropanol is transferred to the a-C of FF by forming six-membered intermediates on the Lewis acidic-basic and Brnsted acidic sites of the UIO-S_(0.6),which is the rate-determining step in the formation of FOL.

Surface passivation in n-type silicon and its application in silicon drift detector

Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon(NAOS)method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition(PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate.The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×10^(15) cm^(-3). When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.