Value-added synthesized acidic polymer nanocomposite with waste chicken eggshell: A novel metal-free and heterogeneous catalyst for Mannich and hantzsch cascade reactions from alcohols

The removal of metals from chemical reactions has raised growing concerns for conserving natural resources and environmental safety. Therefore, it is necessary to expand simple procedures that use eco-friendly materials with high elimination capacities. In this paper, we have synthesized a new nanocomposite material in which eggshell membranes act as nucleation sites for CoFe₂O₄ nanoparticle precipitation in the attendance of an external magnetic field. In the next step anchoring a chlorosulfonic acid on the surface of eggshell‐coated magnetic nanoparticles as solid waste was transformed into a magnetic biomaterial, green, cheap, and environmentally friendly catalyst (CoFe₂O₄@Eggshell@SO₃H). Techniques such as FT-IR, VSM, FESEM, TEM, EDX, XRD, and TGA were used to characterize the as-synthesized catalyst. The catalytic property of the as-prepared catalyst was examined in the synthesis of 2,4,6-triarylpyridine, β-aminocarbonyl, and 2-amino-4,6-diphenylnicotinonitrile via alcohol-based oxidation. Excessive yield, quick reaction time, solvent-free condition, waste to wealth, and optimization with the layout of the experiment are the important advantages of the present work. Taken collectively, these results offer the conversion of wastage to fortune products around the world and utilization in organic metamorphosis.     

Developing Insoluble Polyoxometalate Clusters to Bridge Homogeneous and Heterogeneous Water Oxidation Photocatalysis

Cluster catalysts are attractive for their atomically precise structures, defined compositions, tunable coordination environments, uniform active sites, and their ability to transfer multiple electrons, but they suffer from poor stability and recyclability. Here, we report a general approach to the direct insolubilization of a water soluble polyoxometalate (POM) [{(B-α-PW₉O₃₄)Co₃(OH)(H₂O)₂(O₃PC(O)-(C₃H₆NH₃)PO₃)}₂Co]¹⁴⁻ ( Co₇ ) and formation of a series of POM-based solid catalysts with the counter-cations Ag⁺, Cs⁺, Sr²⁺, Ba²⁺, Pb²⁺, Y³⁺, and Ce³⁺. They exhibit improved catalytic activities for visible-light-driven water oxidation following the trend CsCo₇ > SrCo₇ > AgCo₇ > Ce^IIICo₇ > BaCo₇ > YCo₇ > PbCo₇ . While CsCo₇ exhibits mainly homogeneous catalysis, the others are predominantly heterogeneous catalysts. An optimal oxygen yield of 41.3 % and a high apparent quantum yield (AQY) of 30.6 % for SrCo₇ is obtained, which is comparable to that of the parent homogeneous POM. Band gap structures, UV/Vis spectra, and real-time laser flash photolysis experiments collectively suggest that easier electron transfer from the solid POM catalyst to the photosensitizer promotes photocatalytic water oxidation performance. These solid POM catalysts exhibit good stability, which is directly confirmed by a combination of Fourier-transform infrared spectroscopy, electron microscopy, X-ray diffraction patterns, Raman spectroscopy, X-ray photoelectron spectroscopy, five cycles of tests, and poisoning experiments.     

Synthesis of Cobalt-Tin and -Lead Tetrylidynes—Reactivity Study of the Triple Bond

Tetrylidynes [TbbSn≡Co(PMe₃)₃] ( 1 a ) and [TbbPb≡Co(PMe₃)₃] ( 2 ) (Tbb=2,6-[CH(SiMe₃)₂]₂-4-(t-Bu)C₆H₂) are accessed for the first time via a substitution reaction between [Na(OEt₂)][Co(PMe₃)₄] and [Li(thf)₂][TbbEBr₂] (E=Sn, Pb). Following an alternative procedure the stannylidyne [Ar*Sn≡Co(PMe₃)₃] ( 1 b ) was synthesized by hydrogen atom abstraction using AIBN from the paramagnetic hydride complex [Ar*SnH=Co(PMe₃)₃] ( 4 ) (AIBN=azobis(isobutyronitrile)). The stannylidyne 1 a adds two equivalents of water to yield the dihydroxide [TbbSn(OH)₂CoH₂(PMe₃)₃] ( 5 ). In reaction of the stannylidyne 1 a with CO₂ a product of a redox reaction [TbbSn(CO₃)Co(CO)(PMe₃)₃] ( 6 ) was isolated. Protonation of the tetrylidynes occurs at the cobalt atom to give the metalla-stanna vinyl cation [TbbSn=CoH(PMe₃)₃][BAr^F₄] ( 7 a ) [Ar^F=C₆H₃-3,5-(CF₃)₂]. The analogous germanium and tin cations [Ar*E=CoH(PMe₃)₃][BAr^F₄] (E=Ge 9 , Sn 7 b ) (Ar*=C₆H₃(2,6-Trip)₂, Trip=2,4,6-C₆H₂iPr₃) were also obtained by oxidation of the paramagnetic complexes [Ar*EH=Co(PMe₃)₃] (E=Ge 3 , Sn 4 ), which were synthesized by substitution of a PMe₃ ligand of [Co(PMe₃)₄] by a hydridoylene (Ar*EH) unit.     

Dual Photochemical H-Atom Transfer and Cobalt Catalysis for the Desaturative Synthesis of Phenols from Cyclohexanones

Phenols are integral aromatic molecules widely encountered in the structure of natural products and routinely utilised for the synthesis of high-value materials. Accessing highly substituted derivatives can often be difficult, especially when their functionalization pattern does not match the intrinsic reactivity leveraged by electrophilic aromatic substitution (S_EAr) chemistry. Here, we provide an alternative and mechanistically distinct approach for phenol synthesis using saturated cyclohexanone precursors. This process operates at ambient temperature, under simple purple light irradiation, and features a dual catalytic manifold carrying four sequential H-atom transfer processes.     

Constructions of a set of novel hydrogen-bonded supramolecules from reactions of cobalt(II) salt with bis(3,5-dimethylpyrazolyl)methane and different carboxylic acids

Reactions of CoX₂·6H₂O (X = Cl⁻, ClO₄⁻) with bis(3,5-dimethylpyrazolyl)methane (dmpzm) and formic acid, acetic acid, benzoic acid, salicylic acid, maleic acid, or fumaric acid under the presence of KOH solution produced a new family of Co(II)/dmpzm complexes, [Co(dmpzm)₂L]X·nH₂O (1: L = O₂CH, X = Cl, n = 2; 2: L = OAc, X = Cl, n = 3; 3: L = benzoate, X = ClO₄, n = 1/3; 4: L = salicylate, X = ClO₄, n = 1/3) and [Co₂(dmpzm)₄L](ClO₄)₂·nSolv (5: L = maleate, n = 3, Solv = H₂O; 6: L = fumarate, n = 2, Solv = MeOH). These compounds were structurally characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. Compounds 1–4 are mononuclear while 5–6 are binuclear. Each cobalt atom of 1–6 is hexacoordinate, with a distorted octahedral CoN₄O₂ coordination geometry incorporating two N,N′-bidentate dmpzm ligands and one O,O′-bidentate carboxylate ligand. There are rich intra- and intermolecular hydrogen bonds in the crystals of 1–6, thereby forming either 2D hydrogen-bonded networks (1 and 2) or 3D hydrogen-bonded networks (3–6). In addition, the thermal behaviors of 1–6 were also investigated.     

Construction of quaternary centres for natural polycycles: The Pauson-Khand approach

Construction of quaternary carbons is a challenge in PK chemistry, with few precedents in the literature. Starting from suitable functionalized enynes including an aromatic ring that templates the reaction, polycyclic ketones are obtained with a quaternary carbon. Special reaction conditions are necessary including the use of molecular sieves and co-catalysis with rhodium complexes jointly with cobalt carbonyl. The products obtained are intermediates in the synthesis of various natural products like the Hamigeran family and the steroidic alkaloid Conessine.     

Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1,10-phenanthroline)2 building blocks

Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen)₂(H₂O)(HTST)]·2H₂O (1), [Co₃(phen)₆(H₂O)₂(TST)₂]·7H₂O (2), and [Co₂Cu(phen)₆(H₂O)₂(TST)₂]·10H₂O (3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H₃TST) with the M²⁺ (M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). Complex 1 contains a cis-Co(II)(phen)₂ building block and an HTST as monodentate ligand; complex 2 consists of two TST as bidentate ligands connecting one trans- and two cis-Co(II)(phen)₂ building blocks; complex 3 is formed by replacing the trans-Co(II)(phen)₂ in 2 with a trans-Cu(II)(phen)₂, which is the first reported hetero-trinuclear supramolecular complex containing both the Co(II)(phen)₂ and Cu(II)(phen)₂ as building blocks. The study shows the flexible multifunctional self-assembly capability of the H₃TST ligands presenting in these supramolecular complexes through coordinative, H-bonding and even π-π stacking interactions. The photoluminescent optical properties of these complexes are also investigated and discussed as well as the second-order nonlinear optical properties of 1.     

基于片层结构钴卟啉金属有机骨架的高效氧还原反应电催化剂

使用片层结构的金属有机骨架作为前驱物,通过高温煅烧制备出氮掺杂的介孔碳材料,同时在片层碳骨架上均匀分布着石墨化碳包裹的钴纳米粒子.电化学测试表明,800℃制备的样品具有与铂炭（Pt/C）催化剂相接近的氧还原反应催化活性,催化稳定性和甲醇耐受性良好,显著超越商品化Pt/C催化剂.     

A Cobalt(I) Pincer Complex with an η2‐Caryl−H Agostic Bond: Facile C−H Bond Cleavage through Deprotonation,Radical Abstraction,and Oxidative Addition

The synthesis and reactivity of a Co^I pincer complex [Co(ϰ³P,CH,P‐P(CH)P^NMe‐iPr)(CO)₂]⁺ featuring an η²‐ C_aryl−H agostic bond is described. This complex was obtained by protonation of the Co^I complex [Co(PCP^NMe‐iPr)(CO)₂]. The Co^III hydride complex [Co(PCP^NMe‐iPr)(CNtBu)₂(H)]⁺ was obtained upon protonation of [Co(PCP^NMe‐iPr)(CNtBu)₂]. Three ways to cleave the agostic C−H bond are presented. First, owing to the acidity of the agostic proton, treatment with pyridine results in facile deprotonation (C−H bond cleavage) and reformation of [Co(PCP^NMe‐iPr)(CO)₂]. Second, C−H bond cleavage is achieved upon exposure of [Co(ϰ³P,CH,P‐P(CH)P^NMe‐iPr)(CO)₂]⁺ to oxygen or TEMPO to yield the paramagnetic Co^II PCP complex [Co(PCP^NMe‐iPr)(CO)₂]⁺. Finally, replacement of one CO ligand in [Co(ϰ³P,CH,P‐P(CH)P^NMe‐iPr)(CO)₂]⁺ by CNtBu promotes the rapid oxidative addition of the agostic η²‐C_aryl−H bond to give two isomeric hydride complexes of the type [Co(PCP^NMe‐iPr)(CNtBu)(CO)(H)]⁺.     

氧还原和析氧反应的双功能电催化剂--氮磷共掺碳负载四氧化三钴

金属-空气电池具备诸多优势,譬如绿色环保、能量转化率高、启动快速、能量密度高、使用寿命和干态存储时间长等.与燃料电池相比,金属-空气电池结构简单,放电电压平稳,成本低,但依然存在一些制约发展的问题,如阴极催化剂.阴极催化剂在金属-空气电池中发挥催化氧还原反应(oxygen reduction reaction, ORR)和析氧反应(oxygen evolution reac-tion, OER)的关键作用.铂及其合金常用作 ORR的单功能催化剂,而钌和铱等是目前 OER催化效率最高的,但 ORR活性很低,因此需要开发出一种廉价而又具备双功能催化作用的催化剂.单异原子掺杂的碳基催化剂的研究集中在 ORR催化性能上,而多异原子共掺碳最近有研究表明具有双催化氧的性质,如氮磷共掺碳.在这些氮磷共掺的碳架中,氮磷共掺物起着 OER催化作用,掺氮物为 ORR催化的活性位点,而掺磷物起着强化作用.异原子掺杂负载的钴基催化剂(如掺氮还原氧化石墨烯载 Co3O4)是近年来双功能催化剂研究的另一个热点.钴基催化剂有着催化 ORR和 OER的多价价态,然而其本身导电性能差,这一缺陷可通过杂化石墨化碳来弥补,石墨化碳有着优良的导电性能.据我们所知,目前仍没有关于氮磷共掺碳负载的 Co3O4双催化氧的研究.我们合成了氮磷共掺碳(NPC)负载的 Co3O4(Co3O4/NPC),并首次探索了其氧还原和析氧性能. Co3O4/NPC合成分两步进行.首先通过三聚氰胺与植酸之间的酯化或缩聚覆盖在导电炭黑颗粒表面,在保护气氛下焙烧得到 NPC,然后经溶剂热反应以及空气中氧化合成 Co3O4/NPC.催化剂的性能综合考虑了催化活性和稳定性两方面.采用线性扫描伏安法评估了 OER和 ORR的催化活性.对于 OER, Co3O4/NPC的起始电势是0.54 V (以饱和甘汞电极为参比电极),在0.80 V时电流密度达到21.95 mA/cm2,均优于 Co3O4/C和 NPC. Co3O4/NPC的高效 OER催化可归因于氮磷共掺物与 Co3O4之间的协同作用.对于 ORR, Co3O4/NPC的催化效率与商用 Pt/C相近,它们的扩散极限电流密度分别为–4.49和–4.76 mA/cm2(E =–0.80 V).在 ORR过程中, Co3O4起到主要的催化作用.采用计时电流(电流-时间)法评估了催化剂的稳定性.经6 h测定,对于 OER, Co3O4/NPC剩46%电流;而对于 ORR,剩95%电流.整体而言, Co3O4/NPC在 OER和 ORR中都表现出高的催化效率以及良好的稳定性.