Hierarchical Porous TiO₂ Embedded Unsymmetrical Zinc–Phthalocyanine Sensitizer for Visible-Light-Induced Photocatalytic H₂ Production

In this study, a novel visible-light-driven photocatalyst was designed based on unsymmetrical zinc–phthalocyanine photosensitizer on hierarchical porous TiO₂ (HPT) semiconductor. The HPT material has been prepared by a simple self-formation route. The present work successfully uses zinc phthalocyanine with spectral response extended to 700 nm triggers light harvesting center and HPT semiconductors for high photocatalytic H₂ production. This novel unsymmetrical zinc–phthalocyanine (PCH001) containing three <i>tert</i>-butyl and two carboxylic acid groups that act as “push” and “pull” electron transfer properties from the excited dye to the TiO₂ conduction band. The carboxylic group in the sensitizer serves as an anchoring group on to the surface of TiO₂ and to provide intimate electronic coupling between its excited-state wave function and the conduction-band manifold of the semiconductor. The excellent photophysical properties was governed further by choosing three <i>tert</i>-butyl groups which tuned the LUMO level of the sensitizer that provides directionality in the excited state in addition to low aggregation and high solubility. The Zn-PCH@TiO₂ composites exhibited promising activity and enhanced stability a photocatalytic system for visible-light-induced hydrogen production from water. The photocatalyst (HPT-0.25) shows H₂ production yield 2260 μmol and high turnover number (TON 18080) under visible/near IR light irradiation. Moreover, HPT-0.25 photocatalyst shows a broad visible/NIR light responsive range (400–800 nm) with high apparent quantum yields (AQY) of 7.15, 2.70, 11.57, 3.90, and 0.50% under λ = 420, 550, 690, 730, and 800 nm monochromatic light irradiation, respectively. The present work gives a new advance toward efficient solar energy conversion with promising visible/near IR light-driven photocatalytic activity

Understanding the Structural and Electronic Effect of Zr⁴⁺-Doped KNb(Zr)O₃ Perovskite for Enhanced Photoactivity: A Combined Experimental and Computational Study

Herein, for the first time we report the synthesis of a series of compositionally tunable Zr-doped novel KNb­(Zr)­O₃ perovskites using green and facile methodology and their superior photocatalytic activities toward photoinduced hydrogen production and dye degradation. The substitutional doping of Zr­(IV) in place of Nb­(V) leads to a decrease in the electronic band gap by inclusion of a new acceptor level near the valence band. The results on the optimally doped perovskite for the photocatalytic hydrogen evolution reaction reveal that the 20 mol % Zr-doped KNb­(Zr)­O₃ is 13 times more efficient as compared to the pristine KNbO₃ in terms of rate of H₂ evolution. The same nanocomposite is shown to exhibit 12-fold greater photocatalytic efficiency for degradation of <i>Rhodamine B (</i>RhB) (up to 83% after 210 min) than pure KNbO_3. Density functional theory calculations are carried out to understand the Zr doping effect on the electronic structure as well as the surface hydrogen evolution reaction. Overall, an optimized combination of morphology vs photophysical features synergizes the photocatalytic activity of these newly developed perovskites

An Ester Enolate–Claisen Rearrangement Route to Substituted 4-Alkylideneprolines. Studies toward a Definitive Structural Revision of Lucentamycin A

Substituted 4-alkylideneprolines represent a rare class of naturally occurring amino acids with promising biological activities. Lucentamycin A is a cytotoxic, marine-derived tripeptide that harbors a 4-ethylidine-3-methylproline (Emp) residue unique among known peptide natural products. In this paper, we examine the synthesis of Emp and related 4-alkylideneprolines employing a versatile ester enolate–Claisen rearrangement. The scope and selectivity of the key rearrangement reaction are described with a number of diversely substituted glycine ester substrates. Treatment of the allyl esters with excess NaHMDS at ambient temperature gives rise to highly substituted α-allylglycine products with good to excellent diastereoselectivities. Resolution of dipeptide diastereomers and cyclization to form the pyrrolidine rings provide rapid access to stereopure prolyl dipeptides. We have applied this strategy to the synthesis of four Emp-containing isomers of lucentamycin A in pursuit of a definitive stereochemical revision of the natural product. Our studies indicate that the Emp stereogenic centers are not the source of structural misassignment. The current strategy should find broad utility in the synthesis of additional natural product analogues and related 3-alkyl-4-alkylidene prolines

S‑Scheme ZIF-67/CuFe-LDH Heterojunction for High-Performance Photocatalytic H₂ Evolution and CO₂ to MeOH Production

The S-scheme heterojunction photocatalyst holds potential for better photocatalysis owing to its capacity to broaden the light absorption range, ease electron–hole separation, extend the charge carrier lifespan, and maximize the redox ability. In this study, we integrate zeolitic imidazolate frameworks (ZIFs-67) with the CuFe-LDH composite, offering a straightforward approach towards creating a novel hybrid nanostructure, enabling remarkable performance in both photocatalytic hydrogen (H2) evolution and carbon dioxide (CO2) to methanol (MeOH) conversion. The ZIF-67/CuFe-LDH photocatalyst exhibits an enhanced photocatalytic hydrogen evolution rate of 7.4 mmol g–1 h–1 and an AQY of 4.8%. The superior activity of CO2 reduction to MeOH generation was 227 μmol g–1 h–1 and an AQY of 5.1%, and it still exhibited superior activity after continuously working for 4 runs with nearly negligible decay in activity. The combined spectroscopic analysis, electrochemical study, and computational data strongly demonstrate that this hybrid material integrates the advantageous properties of the individual ZIF-67 and CuFe-LDH exhibiting distinguished photon harvesting, suppression of the photoinduced electron–hole recombination kinetics, extended lifetime, and efficient charge transfer, subsequently boosting higher photocatalytic activities

Single-Atom Ru Catalyst-Decorated CNF(ZnO) Nanocages for Efficient H₂ Evolution and CH₃OH Production

The presence of transition-metal single-atom catalysts effectively enhances the interaction between the substrate and reactant molecules, thus exhibiting extraordinary catalytic performance. In this work, we for the first time report a facile synthetic procedure for placing highly dispersed Ru single atoms on stable CNF(ZnO) nanocages. We unravel the atomistic nature of the Ru single atoms in CNF(ZnO)/Ru systems using advanced HAADF-STEM, HRTEM, and XANES analytical methods. Density functional theory calculations further support the presence of ruthenium single-atom sites in the CNF(ZnO)/Ru system. Our work further demonstrates the excellent photocatalytic ability of the CNF(ZnO)/Ru system with respect to H2 production (5.8 mmol g–1 h–1) and reduction of CO2 to CH3OH [249 μmol (g of catalyst)−1] with apparent quantum efficiencies of 3.8% and 1.4% for H2 and CH3OH generation, respectively. Our studies unambiguously demonstrate the presence of atomically dispersed ruthenium sites in CNF(ZnO)/Ru catalysts, which greatly enhance charge transfer, thus facilitating the aforementioned photocatalytic redox reactions

Single-Atom Ru Catalyst-Decorated CNF(ZnO) Nanocages for Efficient H₂ Evolution and CH₃OH Production

The presence of transition-metal single-atom catalysts effectively enhances the interaction between the substrate and reactant molecules, thus exhibiting extraordinary catalytic performance. In this work, we for the first time report a facile synthetic procedure for placing highly dispersed Ru single atoms on stable CNF(ZnO) nanocages. We unravel the atomistic nature of the Ru single atoms in CNF(ZnO)/Ru systems using advanced HAADF-STEM, HRTEM, and XANES analytical methods. Density functional theory calculations further support the presence of ruthenium single-atom sites in the CNF(ZnO)/Ru system. Our work further demonstrates the excellent photocatalytic ability of the CNF(ZnO)/Ru system with respect to H2 production (5.8 mmol g–1 h–1) and reduction of CO2 to CH3OH [249 μmol (g of catalyst)−1] with apparent quantum efficiencies of 3.8% and 1.4% for H2 and CH3OH generation, respectively. Our studies unambiguously demonstrate the presence of atomically dispersed ruthenium sites in CNF(ZnO)/Ru catalysts, which greatly enhance charge transfer, thus facilitating the aforementioned photocatalytic redox reactions