One-step synthesis of stereo-pure L,L lactide from L-lactic acid

© 2018 Elsevier B.V. Poly (lactic acid) (PLA) is extensively used as an eco-friendly compound for many applications. The synthesis of stereo-pure lactide, specifically L,L-lactide which is the most desired isomer for the synthesis of high-quality PLA is very important. In this work, various materials including MOFs and simple bases have been applied as catalysts for the Lactide synthesis. Herein we report the one-step synthesis of L,L-lactide with high selectivity and yield (99%) in the absence of racemization by applying a cost-effective Cs2CO3 catalyst. The novel described procedure is even expected to be very efficient for industrial applications.status: publishe

Spray drying of zeolitic imidazolate frameworks : investigation of crystal formation and properties

High-quality zeolite imidazole frameworks (ZIF-8, ZIF-67, and bimetallic Zn/Co-ZIF) were synthesized using the spray-drying technique and the mechanism of crystal growth during the whole process is discussed. It is also demonstrated that the crystallization mechanism for N-donor containing ditopic imidazolate (IM) ligands forming ZIF structures is divergent from MOF formation applying carboxylate ligands, and their formation using the spray dry method occurs via a unique mechanism. An intermediate amorphous phase was obtained after spray drying the feed solution, and the crystallographic ZIF structure was obtained during immersion in a solvent. Several characterization techniques, such as FTIR, XRD, SEM, porosity analysis, elemental analysis etc., were applied to examine the characteristic properties of materials, including, intermediate compounds and final products. The results proved that the spray drying procedure is a facile, continuous and effective synthetic route to produce MOFs (ZIFs) in higher quantities with high-quality properties such as high porosity, a large surface area, more active catalyst sites, etc. applying a minimum amount of time and energy which is unusual in common synthesis methods of MOFs

Enhanced Performance of Carbon–Selenide Composite with La0.9Ce0.1NiO3 Perovskite Oxide for Outstanding Counter Electrodes in Platinum-Free Dye-Sensitized Solar Cells

For large-scale applications, dye-sensitized solar cells (DSSCs) require the replacement of the scarce platinum (Pt)-based counter electrode (CE) with efficient and cheap alternatives. In this respect, low-cost perovskite oxides (ABO3) have been introduced as promising additives to composite-based CEs in Pt-free DSSCs. Herein, we synthesized composites from La0.9Ce0.1NiO3 (L) perovskite oxide and functionalized-multiwall-carbon-nanotubes wrapped in selenides derived from metal-organic-frameworks (f-MWCNT-ZnSe-CoSe2, “F”). L and F were then mixed with carbon black (CB) in different mass ratios to prepare L@CB, F@CB, and L@F@CB composites. The electrochemical analysis revealed that the L@F@CB composite with a mass ratio of 1.5:3:1.5 exhibits better electrocatalytic activity than Pt. In addition, the related DSSC reached a better PCE of 7.49% compared to its Pt-based counterpart (7.09%). This improved performance is the result of the increase in the oxygen vacancy by L due to the replacement of La with Ce in its structure, leading to more active sites in the L@F@CB composites. Moreover, the F@CB composite favors the contribution to the high electrical conductivity of the hybrid carbon nanotube–carbon black, which also offers good stability to the L@F@CB CE by not showing any obvious change in morphology and peak-to-peak separation even after 100 cyclic voltammetry cycles. Consequently, the corresponding L@F@CB-based device achieved enhanced stability. Our work demonstrates that L@F@CB composites with a low cost are excellent alternatives to Pt CE in DSSCs