This work reports the design and preparation of a recyclable fibrous heterogeneous photocatalyst (PANRB-4F) for visible-light-induced, metal-free C–heteroatom bond formation. The catalyst was prepared by immobilizing the organic dye photosensitizer Rose Bengal onto a polyacrylonitrile-based fibrous support, providing a stable heterogeneous platform for photoredox catalysis. The immobilization ensures firm integration of the photoactive species within the high-surface-area fibrous architecture, enabling efficient light harvesting and creating a convenient solid–liquid interfacial environment for the reactions. Under visible-light irradiation, PANRB-4F efficiently promotes thiocyanation and selenylation of Indoles at room temperature (25 °C). A wide range of substrates bearing diverse functional groups are well tolerated under these mild conditions, affording the corresponding products in generally good to excellent yields. These transformations proceed without the use of metal catalysts, highlighting the environmentally friendly nature of the system. Importantly, the heterogeneous fibrous catalyst can be easily recovered by simple physical separation and reused for multiple cycles with negligible loss of activity, demonstrating excellent operational stability. Overall, this study shows that immobilizing organic photosensitizers on fibrous polymer supports provides a practical, metal-free, and recyclable photocatalytic platform for visible-light-driven C–heteroatom bond-forming transformations.
Although decatungstate (DT) photocatalysis has advanced rapidly, applications for net-oxidative transformations without external oxidants remain limited, primarily due to DT's inherent propensity to favor redox-neutral pathways. Herein, we report two electrophotocatalytic dehydrogenative cyclizations utilizing aldehydes with N-acryloyl aldehyde hydrazones or N-acryloylbenzamides. Using tetrabutylammonium decatungstate (TBADT) as a hydrogen atom transfer photocatalyst, these transformations afford aroylated dihydropyrazoles and isoquinoline-1,3-diones with retention of the ketone moiety. This protocol features oxidant-free, acid-free, and base-free conditions, a stoichiometric charge of 2 F mol–1, and a robust functional group tolerance. Demonstrations include gram-scale synthesis, sunlight-driven operation, and an all-solar-driven setup powered by photovoltaic panels, collectively underscoring the practicality and sustainability of this method.
A series of novel phosphorus-free nitrogen-containing heterogeneous hydroformylation catalysts based on porous aromatic frameworks (PAFs) were designed and synthesized. Among them, PAF-EDA-Rh (EDA=ethylene diamine fragment) demonstrated the lowest Rh leaching and stable oxygenates yields in five consecutive runs. Additionally, it was active in hydrogenation of the produced aldehydes, i.e. promoted reductive hydroformylation tandem reaction. At longer reaction times, alcohols were the dominant products. By FTIR, XPS, and XAS methods, it was established that in fresh PAF-EDA-Rh catalyst Rh presents as highly-coordinated Rh3+ species. After reaction, the carbonyl complexes with lower coordination number and Rh oxidation state, which are supposed to be active species, are formed. The activity of PAF-EDA-Rh in reductive hydroformylation of various substrates demonstrates its potential for the use in one-step synthesis of primary alcohols from olefins.
High-temperature oxidation reactions driven by lattice oxygen on metal oxide catalysts are crucial for numerous industrial transformation processes. However, the catalytic performance is often limited by the inherently sluggish migration rate of stable lattice oxygen in conventionally synthesized catalysts under high temperatures. Herein, we pre-treated the TiO2 support via high-temperature reduction to generate abundant surface defect sites. Subsequent leveraging the defect anchoring effect during integration with V2O5 to drive the formation of interfacial miscibilited V2O5/TiO2 catalyst with lattice distortion. This strategy, accompanied by a high density of oxygen vacancies, promote spontaneous migration of lattice oxygen at high-temperature and its participation in the catalytic cycle. Compared to conventional V2O5/TiO2, the modified V2O5/TiO2 catalyst demonstrates an approximately threefold enhancement in the initial reaction rate (0.59mol/(gcat∙ s)) for the oxidation of 3-methylpyridine. This enhancement is attributed to the interfacial miscibilited V2O5/TiO2 catalyst exhibit improved electron transfer capability and O2 activation rate, thereby synergistically facilitating the key activation of C-H bond in the oxidation process. The findings in this work provide an effective catalyst design strategy for enhancing high-temperature catalytic oxidations through deliberate lattice engineering.
The development of efficient metal-free photocatalysts is of great importance for advancing solar-driven CO2 conversion. Graphitic carbon nitride (g-C3N4) has attracted extensive attention due to its unique electronic structure and excellent stability; however, its photocatalytic efficiency is severely limited by rapid photogenerated charge carrier recombination. Herein, we construct a metal-free COFV/CNNS heterojunction by exploiting the electronic disparity between electron-rich carbon nitride nanosheets (CNNS) and an electron-deficient π-conjugated covalent organic framework (COFV). A polyethyleneimine (PEI)-mediated surface modification strategy is employed to regulate interfacial assembly and enhance interfacial contact between the two components. The intimate heterointerface induces interfacial charge redistribution driven by the intrinsic electronic disparity between CNNS and COFV, leading to the formation of a built-in electric field at the interface through Fermi-level equilibration and electronic coupling. This internal electric field, together with the strong interfacial interaction, promotes efficient separation and directional migration of photogenerated charge carriers, thereby suppressing recombination and significantly enhancing photocatalytic performance. The optimized COFV/CNNS-60 composite exhibits a CO evolution rate of 14.8 times that of pristine CNNS and 3.9 times that of COFV under visible-light irradiation (λ ≥ 420 nm) in pure water without any sacrificial agents. This work provides a general strategy for constructing high-performance metal-free photocatalysts via interfacial electronic regulation and interface engineering, offering new insights into sustainable solar-to-fuel conversion.
The selective partial hydrogenation of pyridine rings, particularly in functionalized nitrogen heterocycles, remains a significant challenge due to the tendency of conventional catalysts to over-hydrogenate or exhibit poor regioselectivity. Herein, we report a bimetallic PdCo/C catalyst supported on coconut shell carbon (CSC), synthesized via a simple impregnation method, for the selective hydrogenation of methyl nicotinate to methyl 3-tetrahydropyridinecarboxylate (MTPC). Comprehensive characterization by XRD, SEM, and N2 adsorption-desorption confirms the formation of a micro-mesoporous carbon architecture with uniformly dispersed Pd-Co bimetallic particles. Catalytic evaluation reveals a pronounced synergistic effect between Pd and Co, wherein Pd doping modifies the electronic properties of Co and optimizes the catalyst surface for partial hydrogenation. Systematic investigation of metal loading, reaction temperature, and time establishes that the optimized 1%Pd-10%Co/C-350 catalyst achieves complete conversion of methyl nicotinate with 86.0% selectivity toward MTPC under mild conditions (70 °C, 2 h), while successfully preserving the ester functionality. This work demonstrates that bimetallic synergy in PdCo/C provides an effective strategy for controlling chemoselective hydrogenation of pyridine derivatives, offering a promising and sustainable approach for the selective reduction of nitrogen-containing heteroaromatic compounds.
