No abstract

No abstract

We have successfully substituted trivalent Bi3+ with divalent Pb2+ in Cs3Bi2Br9-layered perovskites. Controlled heterovalent Pb substitution in these Cs3Bi2Br9-layered perovskites reduces the band gap because of the emergence of defect states in between the bands. These heterovalent Pb-substituted Cs3Bi2Br9 bulk perovskite compounds are successfully synthesized for the first time by chemical reprecipitation method. X-ray photoelectron spectroscopy analysis indicate that lead substitution in the structure is in Pb2+ form, which creates a charge imbalance in the compound as it replaces Bi3+ from the layered perovskite structure. Such charge imbalance is compensated either by bromine vacancies (VBr) or interstitial cesium (Csi) additions. VBr or Csi in Cs3Bi2Br9 along with PbBi creates defect states in between the bands, which results in redshift in the layered perovskite band. Band structure calculations indeed confirm the onset of such defect states, responsible for the redshift. A more detailed defect physics simulation indicates that the defect complex PbBi + VBr is more probable to form if Pb is rich in the environment, which consequently introduces a few deep level defects responsible for the reduction of the band gap. Understanding of the electronic structure and defect physics of such heterovalent Pb-substituted Cs3Bi2Br9 will strengthen the future photovoltaic and optoelectronic applications.

No abstract

Unique mesoporous silicoaluminophosphate (MESO-SAPO-37) with uniform pores (3 nm) was synthesized for the first time by using a faujasite-type microporous SAPO-37 precursor. MESO-SAPO-37 contains hierarchical mesopores with a microporous secondary building unit. It possesses strong acidity and shows high catalytic activity for the conversion of 1-octene, with the exclusive formation of isomerized products (84%).

Organo‐functionalized materials with porous structure offer unique adsorption, catalytic and sensing properties. These unique properties make them available for various applications, including catalysis, CO2 capture and utilization, and drug delivery. The properties and the performance of these unique materials can be altered with suitable modifications on their surface. In this review, we summarize the recent advances in the preparation and applications of organo‐functionalized porous materials with different structures. Initially, a brief historical overview of functionalized porous materials is presented, and the subsequent sections discuss the recent developments and applications of various functional porous materials. In particular, the focus is given on the various methods used for the preparation of organo‐functionalized materials and their important roles in the heterogenization of homogeneous catalysts. A special emphasis is also given on the applications of these functionalized porous materials for catalysis, CO2 capture and drug delivery.

Ordered mesoporous silicoaluminophosphate (MESO-SAPO-34) assembled from microporous SAPO-34 precursor was stabilized by post synthesis vapor phase treatment. The resultant MESO-SAPO-34 possessed uniform mesoporosity, high surface area, pore volume, and strong acidity. The resultant materials were studied as catalysts for the hydroisomerization of 1-octene and showed excellent conversion, and a maximum branched isomer selectivity of about 52% was achieved at low weight hourly space velocity (WHSV). Kinetic models based on Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism were developed to describe the hydroisomerization of 1-octene, and the kinetics and adsorption parameters were estimated. A nonlinear regression based on modified Levenberg–Marquardt algorithm was used to estimate the parameters, and the model values were found to compare well with the experimental values. Parameters obtained from the LHHW model show that the conversion of 1-octene to other linear octenes requires low activation energy, whereas the conversion of linear octene to branched octene demands the highest activation energy. The enthalpy and entropy of adsorption obtained from Arrhenius plots were found to be consistent with thermodynamics.

No abstract