Baylis–Hillman Reaction as a Versatile Platform for the Synthesis of Diverse Functionalized Polymers by Chain and Step Polymerization

The Baylis–Hillman reaction, which is a carbon–carbon bond forming reaction between an aldehyde and an activated alkene, was utilized to prepare densely functionalized monomers suitable for chain and step polymerization. By reacting formaldehyde with various alkyl acrylates, a series of alkyl α-hydroxymethyl acrylate monomers were synthesized. These monomers efficiently underwent RAFT polymerization to provide α-hydroxymethyl-substituted polyacrylates with well controlled molecular weight and low polydispersity. The resulting homopolymers were also efficient macro-chain transfer agents for further RAFT polymerization. The Baylis–Hillman reaction was also utilized to synthesize alkene functionalized diols which underwent step-growth polymerization to provide polyesters and poly­(ester urethane)­s. Furthermore, it was demonstrated that the alkene group can be quantitatively functionalized by thiol–ene click chemistry to provide a series of polymers with diverse physical properties

Identifying the Role of Photogenerated Holes in Photocatalytic Methanol Dissociation on Rutile TiO₂(110)

As an important model reaction, photocatalytic methanol dissociation on rutile TiO₂(110) has drawn much attention, but its reaction mechanism remains elusive. Using DFT+U calculations, we investigate the whole dissociation process of methanol into formaldehyde with and without photogenerated holes, aiming to illustrate how the hole is involved in the dissociation. We find that the O–H dissociation of methanol is a heterolytic cleavage process and is likely to be thermally driven; the presence of a hole has no promotion on the barrier and enthalpy change. In contrast, the subsequent C–H bond cleavage follows the homolytic cleavage mode and is likely to be photochemically driven; great enhancement can be made in both kinetics and thermodynamics when holes are introduced. The essential roles of holes in promoting C–H dissociation are identified, and what kinds of catalytic reactions can or cannot be facilitated by holes is discussed. Our findings may considerably broaden the understanding of photocatalytic chemistry

Unique Trapped Dimer State of the Photogenerated Hole in Hybrid Orthorhombic CH₃NH₃PbI₃ Perovskite: Identification, Origin, and Implications

Revealing the innate character and transport of the photogenerated hole is essential to boost the high photovoltaic performance in the lead-based organohalide perovskite. However, knowledge at the atomic level is currently very limited. In this work, we systematically investigate the properties of the photogenerated hole in the orthorhombic CH₃NH₃PbI₃ using hybrid functional PBE0 calculations with spin–orbit coupling included. An unexpected trapping state of the hole, localized as I₂^– (I dimer), is uncovered, which was never reported in photovoltaic materials. It is shown that this localized configuration is energetically more favorable than that of the delocalized hole state by 191 meV and that it can highly promote the diffusion of the hole with an energy barrier as low as 131 meV. Furthermore, the origin of I dimer formation upon trapping of the hole is rationalized in terms of electronic and geometric effects, and a good linear correlation is found between the hole trapping capacity and the accompanying structural deformation in CH₃NH₃PbX₃ (X = Cl, Br, and I). It is demonstrated that good CH₃NH₃PbX₃ materials for the hole diffusion should have small structural deformation energy and weak hole trapping capacity, which may facilitate the rational screening of superior photovoltaic perovskites

RSCU values in the mitogenome of <i>Conus quercinus</i>.

<p>Codon families are indicated below the X-axis.</p

D-loop length of <i>Conus</i> mitogenomes.

<p>D-loop length of <i>Conus</i> mitogenomes.</p

Ka/Ks ratios for the 13 mitochondrial PCGs among three representative <i>Conus</i> species.

<p>GenBank accession numbers: KY609509 for <i>C</i>. <i>quercinus</i>, NC_008797 for <i>C</i>. <i>textile</i>, and NC_030536 for <i>C</i>. <i>striatus</i>.</p

The phylogenetic tree of <i>Conus</i> species based on 13 complete mitogenome sequences.

<p>GenBank accession numbers: NC_008098.1 for <i>L</i>. <i>cerithiformis</i>, NC_008797.1 for <i>C</i>. <i>textile</i>, NC_013239.1 for <i>O</i>. <i>dimidiate</i>, NC_013242.1 for <i>F</i>. <i>similis</i>, NC_013243.1 for <i>C</i>. <i>borgesi</i>, NC_023460.1 for <i>C</i>. <i>consors</i>, NC_027518.2 for <i>C</i>. <i>tulipa</i>, NC_027957.1 for <i>C</i>. <i>tribblei</i>, NC_030213.1 for <i>C</i>. <i>gloriamaris</i>, NC_030354.1 for <i>C</i>. <i>capitaneus</i>, NC_030536.1 for <i>C</i>. <i>striatus</i>, and NC_032377.1 for <i>C</i>. <i>californicus</i>. The red branch highlights our present study of <i>C</i>. <i>quercinus</i>. Please note that the outgroups <i>L</i>. <i>cerithiformis</i>, <i>O</i>. <i>dimidiata</i> and <i>F</i>. <i>similis</i> are allochthonous species. Branch lengths and topologies were obtained using the Bayesian inference analysis.</p

Scheme of the D-loop region in <i>C</i>. <i>quercinus</i> compared with <i>C</i>. <i>consors</i>.

<p>The region spans 943 bp and exhibits several outstanding motifs. The upper and lower red boxes denote the tRNA-Phe and COX3, and the blue box points to a long AT tandem repeat stretch.</p

Nucleotide composition of <i>Conus</i> mitogenomes.

<p>Nucleotide composition of <i>Conus</i> mitogenomes.</p

Hybrids of Two-Dimensional Ti₃C₂ and TiO₂ Exposing {001} Facets toward Enhanced Photocatalytic Activity

Effectively harvesting light to generate long-lived charge carriers to suppress the recombination of electrons and holes is crucial for photocatalytic reactions. Exposing the highly active facets has been regarded as a powerful approach to high-performance photocatalysts. Herein, a hybrid comprised of {001} facets of TiO₂ nanosheets and layered Ti₃C₂, an emerging 2D material, was synthesized by a facile hydrothermal partial oxidation of Ti₃C₂. The in situ growth of TiO₂ nanosheets on Ti₃C₂ allows for the interface with minimized defects, which was demonstrated by high-resolution transmission electron microscopy and density functional theory calculations. The highly active {001} facets of TiO₂ afford high-efficiency photogeneration of electron–hole pairs, meanwhile the carrier separation is substantially promoted by the hole trapping effect by the interfacial Schottky junction with 2D Ti₃C₂ acting as a reservoir of holes. The improved charge separation and exposed active facets dramatically boost the photocatalytic degradation of methyl orange dye, showing the promise of 2D transition metal carbide for fabricating functional catalytic materials