Whatever the chemistry used for the synthesis of aliphatic polycarbonates, in particular, those of high molar mass, the adventitious presence of water leads to bimodal GPC traces and affords polycarbonate samples of uncontrolled and unpredictable molar masses. It appears that among all reagents used in the copolymerization of CO2 and epoxides, CO2 is the most difficult one to dry. To address this issue, triisobutylaluminum (TiBA) was employed in this work to dry CO2 through a bubbling method; its drying capability was investigated in the context of the copolymerization of CO2 with epoxides initiated by onium chloride in the presence of triethylborane (TEB). It was then compared to the efficiency of other already reported drying agents such as phosphorus pentoxide, molecular sieves and commercially available CO2 purifiers. With TiBA-dried CO2, its copolymerizations respectively with propylene oxide (PO) and cyclohexene oxide (CHO) could be successfully achieved in a wide range of degrees of polymerization (DP), with the value of DP as high as 16000. Diblock copolymers poly(propylene carbonate-b-cyclohexene carbonate) (PPC-b-PCHC) could also be prepared through sequential addition of epoxide monomers. The polycarbonates obtained under the conditions were all well-defined as characterized by NMR, GPC, triple detector-GPC, and differential scanning calorimetry (DSC).

Efficient reduction of cyclic and linear organic carbonates catalyzed by a readily available earth alkaline catalyst has been achieved. The described homogenous reaction based on a ligand-free magnesium catalyst provides an indirect route for the conversion of CO2 into valuable alcohols. The reaction proceeds with high yields under mild reaction conditions, with low catalyst loading and short reaction times, and shows a broad applicability toward various linear and cyclic carbonates. Additionally, it can be applied for the depolymerization of polycarbonates.

Artificial metalloenzymes (ArMs) have high potential in biotechnological applications as they combine the versatility of transition-metal catalysis with the substrate selectivity of enzymes. An ideal host protein should allow high-yield recombinant expression, display thermal and solvent stability to withstand harsh reaction conditions, lack nonspecific metal-binding residues, and contain a suitable cavity to accommodate the artificial metal site. Moreover, to allow its rational functionalization, the host should provide an intrinsic reporter for metal binding and structural changes, which should be readily amendable to high-resolution structural characterization. Herein, we present the design, characterization, and de novo functionalization of a fluorescent ArM scaffold, named mTFP*, that achieves these characteristics. Fluorescence measurements allowed direct assessment of the scaffold's structural integrity. Protein X-ray structures and transition metal Förster resonance energy transfer (tmFRET) studies validated the engineered metal coordination sites and provided insights into metal binding dynamics at the atomic level. The implemented active metal centers resulted in ArMs with efficient Diels-Alderase and Friedel-Crafts alkylase activities.

A highly easy and efficient metal-free methodology for the synthesis of polyaziridine-based polymers with controlled architectures and desired functionalities was developed by organocatalytic ring-opening polymerization (ROP) of N-sulfonyl aziridines with a carboxylic acid as initiator. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (MTBD) and phosphazene t-Bu-P4 organocatalysts have demonstrated high catalytic efficiency in connection with the controlled/living character of the ROP of 2-methyl-N-tosylaziridines (TsMAz) initiated by benzoic acid. Aryl carboxylic acids bearing an azido or a hydroxyl group as well as bio-derived vanillic acid and syringic acid and alkyl- and alkenyl-substituted carboxylic acids, such as acetic acid, palmitic acid, and methacrylic acid, can all initiate the ROP of TsMAz toward well-defined P(TsMAz)s. α,ω-Diamino telechelic, star-shaped P(TsMAz)s, and poly(styrene-co-methacrylic acid)-graft-poly(2-methyl-N-tosylaziridine) [P(St-co-MAA)-g-P(TsMAz)] have been conveniently synthesized from the corresponding multicarboxyl (macro)initiators. Finally, this protocol has been applied for the synthesis of a linear photoresponsive P(TsMAz) and an aggregation-induced emission (AIE)-active 4-arm P(TsMAz) star from the corresponding functionalized carboxylic acids.

An unprecedented nickel-catalyzed decarbonylative silylation via CO extrusion intramolecular recombination fragment coupling of unstrained and nondirecting group-Assisted silyl ketones is described. The inexpensive and readily available catalyst performs under mild reaction conditions and enables the synthesis of structurally diverse arylsilanes, including heterocyclic and natural product derivatives.

Producing aromatics directly from the smallest hydrocarbon building block, methane, is attractive because it could help satisfy increasing demand for aromatics while filling the gap created by decreased production from naphtha crackers. The system that catalyzes the direct methane dehydroaromatization (MDA) best so far is Mo supported on zeolite. Mo has shown to outperform other transition metals (TMs). Here we attempt to explain the superiority of Mo by directly comparing Fe and Mo supported on HZSM-5 zeolite. To determine the most important parameters responsible for the superior performance of Mo, detailed characterization using X-ray absorption spectroscopy (XAS) techniques combined with catalytic testing and theoretical calculations are performed. The higher abundance of mono- and dimeric sites for the Mo system, their ease of carburization in methane, as well as intrinsically lower activation energy barriers of breaking the methane C–H bond over Mo explain the better catalytic performance. In addition, a pretreatment in CO is presented to more easily carburize Fe and thereby improve its catalytic performance.

A simple and efficient catalytic system for a chemo- and regioselective ortho-alkenylation of anilines is presented. The new magnesium-catalyzed reaction allows the use of a wide range of alkynes and anilines with different electronic and steric properties and provides free as well as protected anilines with excellent yields.

Hot carrier (HC) cooling is a critical photophysical process that significantly influences the optoelectronic performance of hybrid perovskite-based devices. The hot carrier extraction at the device interface is very challenging because of its ultrashort lifetime. Here, ultrafast transient reflectance spectroscopy measurements and time-domain ab initio calculations show how the dielectric constant of the organic spacers can control and slow the HC cooling dynamics in single-crystal 2D Ruddlesden–Popper hybrid perovskites. We find that (EA)2PbI4 (EA = HOC2H4NH3+) that correspond to a high dielectric constant organic spacer has a longer HC cooling time compared to that of (AP)2PbI4 (AP = HOC3H6NH3+) and (PEA)2PbI4 (PEA = C6H5C2H4NH3+). The slow HC relaxation process in the former case can be ascribed to a stronger screening of the Coulomb interactions, a small nonradiative internal conversion within the conduction bands, as well as a weak electron–phonon coupling. Our findings provide a strategy to prolong the hot carrier cooling time in low-dimensional hybrid perovskite materials by using organic spacers with reduced dielectric confinement.

We demonstrate enhancement of the photoluminescence (PL) properties of individual zero-dimensional (0D) Cs4PbBr6 perovskite nanocrystals (PNCs) upon encapsulation by alumina using an appropriately modified atomic layer deposition method. In addition to the increased PL intensity and improved long-term stability of encapsulated PNCs, our single-particle studies reveal substantial changes in the PL blinking statistics and the persistent appearance of the long-lived, “delayed” PL components. The blinking patterns exhibit a modification from the fast switching between fluorescent ON and OFF states found in bare PNCs to a behavior with longer ON states and more isolated OFF states in alumina-encapsulated PNCs. Controlled exposure of 0D nanocrystals to moisture suggests that the observed PL lifetime changes may be related to water-induced “reservoir” states that allow for longer-lived charge storage with subsequent back-feeding into the emissive states. Viable encapsulation of PNCs with metal oxides that can preserve and even enhance their PL properties can be utilized in the fabrication of extended structures on their basis for optoelectronic and photonic applications.

Shaping and optimal compositional formulation are major challenges in the successful industrial application of heterogeneous catalysts. The choice of components during formulation plays a vital role in endowing the final catalyst's mechanical strength, durability, and lifetime and may even affect activity and selectivity. Herein, we evaluate the application of spray drying to manufacture spherical ZSM-5-based catalysts and their applicability in the methanol-to-olefins process. Several critical parameters of the spray drying process and various aspects related to catalyst formulation (binder, zeolite, and clay) are investigated. Chemical composition and structure of the clay matrix substantially influence the catalytic performance.