Showing papers by "Zhen Hua Li published in 2018"

Undercoordinated Site-Abundant and Tensile-Strained Nickel for Low-Temperature COx Methanation

Abstract: By means of the rapid quenching (RQ) technique, we fabricate RQ Ni with peculiar undercoordinated site (UCS) abundant and tensile-strained structural characteristics. In liquid-phase CO methanation at 473 K, RQ Ni displays markedly higher specific activity and CH4 selectivity in comparison to Raney Ni, supported Ni, and Al2O3-supported Pd and Pt. RQ Ni shows comparable activity but higher CH4 selectivity in comparison to Ru/Al2O3, with Ru being documented as the most active metal for CO methanation. Density functional theory (DFT) calculations confirm that the UCSs are the active centers and reveal that the tensile-strain effect can further accelerate the rate-limiting CO dissociation step. Attractively, RQ Ni is also powerful in converting the greenhouse gas CO2 to CH4 at 473 K with an unprecedentedly high TOF of CO2 of 86.9 × 10–3 s–1 and impressively high selectivity of >99%.

Highly Stable Molecular Borromean Rings

Abstract: A series of Cp*Rh-based molecular Borromean rings (BRs) are prepared from naphthazarine or metallaligand. Some of as-synthesized BRs display high stability and are formed in high yields in solution. The reason is related to the length ratio of the long-arm linker and short-arm linker, where smaller aspect ratios of the metallarectangles promote improved stability and yields of the BRs in solution. Increasing the width of the metallaligand or pyridyl ligand hinders the formation of BRs and leads to unoccupied monomeric rectangles, which were further used as catalysts for the acyl transfer reaction between N-acetylimidazole and (4-(pyridin-4-yl)phenyl) methanol.

Addition of dihydrogen to a borylborenium center

Abstract: The activation of a H–H bond, the simplest covalent bond, is a fundamentally important process. Addition of H2 to an elemental center typically occurs on low valent transition metal or main group complexes through oxidative addition to afford metal dihydride complexes. In contrast, activation of H2 on a high valent center generally results in heterolytic cleavage of the H–H bond to a proton and hydride. Here, we report experimental and computational evidence for the addition of H2 to a borenium center in an N-heterocyclic carbene (NHC) coordinated borylborenium cation, which leads to the formation of a dihydroborenium complex accompanied by the elimination of two σ-bonded substituents, namely mesityl (Mes) and pinacolboryl (Bpin) groups, as mesitylboronic ester.

Synthesis of an oxygen-linked germinal frustrated Lewis pair and its application in small molecule activation

Abstract: Reaction of Mes2P(O)Li with (C6F5)2BCl gave access to an oxygen-linked germinal intramolecular frustrated Lewis pair Mes2P(O)B(C6F5)2 (1) Compound 1 is stable at room temperature and only decomposes when heated to 90 °C NMR analysis and theoretical analysis revealed the frustrated nature between the boron and phosphorus centers Compound 1 shows typical frustrated Lewis pair reactivity when treated with dihydrogen, carbon dioxide, alkyne and alkene The reaction of 1 with isoprene resulted in selective formation of 3,4-phosphoryl/boryl addition product 8

Designing Metal-Free Frustrated Lewis Pairs Catalyst for the Efficient Dehydrogenation of Ammonia Borane.

Abstract: Ammonia borane (AB) has been in the spotlight for the chemical storage of hydrogen over the past decade. However, the development of methods for efficient and controlled hydrogen release from AB under mild conditions is still underway. Herein, using density functional theory (DFT) computations, we designed a metal-free frustrated Lewis pair (FLP) catalyst o-(BPh2 )C6 H4 (NiPr2 ) (M1) that can efficiently dehydrogenate AB to release more than two equivalents of H2 under mild conditions. Catalyst M1 can dehydrogenate not only AB to H2 N=BH2 (AOB) and H2 , but also oligomers of AOB with rather low free-energy barriers. The high dehydrogenation activity of M1 is the key of new oligomerization routes to the efficient dehydrogenation of AB to borazine (BZ) or H2 B-(NH=BH)n -NH2 (PIB) and finally to polyborazylene (PBZ) so that more than two equivalents of H2 can be released. A first-principle kinetic Monte Carlo (KMC) study reveals that the activity of our catalytic system can be tuned by varying the initial concentration of M1 and AB. This work can guide the design of catalyst for the highly efficient utilization of AB as a hydrogen storage material.

Chiral Ferrocenyl N,N Ligands with Intramolecular Hydrogen Bonds for Highly Enantioselective Allylic Alkylations

Abstract: Several novel ferrocene-derived bidentate nitrogen ligands, which were incorporated with multi-chiral factors, have been designed and synthesized by rational combination of oxazoline and pyridine. Their catalytic performances were preliminarily investigated in palladium-catalyzed asymmetric allylic alkylation, and excellent reactivities and enantioselectivities (up to 99% yield and 98% ee) were realized using the ligand with matched chirality. DFT calculations illustrated that an intramolecular hydrogen bond formed between the hydroxyl group and the oxazoline fragment of the ligand contributed to the optimal conformation of the ligand-Pd-allyl complex.

Method for preparing multi-ion embedded supercapacitor with electrochemical alkaline activation

Abstract: A method for preparing a multi-ion embedded supercapacitor with electrochemical alkaline activation. A simple and rapid electrochemical alkaline activation method is employed to perform activation or deactivation processing on a transition metal hydroxide containing cobalt or nickel to realize intelligent regulation and control of the hydroxide electrode materials to storage capacity of various metal cations, and is applied to an ion embedded supercapacitor. Provided is a universal method capable of improving storage capacity of electrode materials of an ion embedded supercapacitor, and the range of application of the transition metal hydroxide electrode materials is further widened in the field of energy storage.