The strain and ligand effects on the adsorption energies of key intermediates (*COOH, *CO, *CHO, and *COH) in CO2 reduction reactions on the Cu–M(111) (M = Ni, Co, Cu, Rh, Ir, Pd, Pt) heterolayered catalysts have been quantitatively separated using first-principles calculations. Contrary to the common belief that strain is always the leading factor influencing catalytic performance of the core–shell type heterostructure catalysts, the ligand effect due to the underlying hetero elements should not be ignored and may become dominant for strain-insensitive adsorbates (*CO and *COH). Moreover, the models of Cu(2 ML/3 ML)–M(111) (M = Ir, Rh, Pt, Pd) have been shown to be better catalysts for CO2 reduction, as they require lower overpotential to drive the reaction than the Cu(111) slab. Particularly, the overpotential is predicted to be lowered by 0.17 V for Cu(3 ML)–Ir(111) model catalyst. Thus, both effects should be considered in heterostructure catalyst design.

Thirteen new 1,3-substituted imidazolium poly(azolyl)borate salts with the general formula [R1R2im][B(H)4−n(azolyl)n] (R1 = methyl, n-butyl, 2-(diethylamino)ethyl; R2 = methyl; azolyl = pyrazolyl, imidazolyl, 1,2,4-triazolyl, tetrazolyl; n = 2, 3) have been synthesized through salt metathesis of the corresponding imidazolium chloride and potassium poly(azolyl)borates. The newly synthesized dihydrobis(azolyl)borate and hydrotris(azolyl)borate salts are liquids at room temperature except two of the 1,3-dimethylimidazolium derivatives, [mmim][H2B(pz)2] and [mmim][HB(pz)3]. Conductivity, thermal and physicochemical properties of the new borate ionic liquids were systematically investigated. With multiple azolyl groups serving as binding sites, these ionic liquids (ILs) generally exhibit high SO2 absorption capacity (up to 5.8 mol mol−1 of IL or 1.05 g g−1 of IL for 1-methyl-3-n-butylimidazolium hydrotris(imidazolyl)borate, compound 13).

Cation-assisted interactions between N-containing heterocycles (NHCs) and CO2 have been systematically studied by using density functional theory (DFT). For neutral and anionic (non-carbenoid) NHCs, the effects of monovalent cations (i.e., alkali metal ions) are moderate to small (the NHC–CO2 binding energy change, ΔBE usually < 25 kJ mol−1). However, for NHC carbenes, due to their strong basicity, the effects are strong (ΔBE > 60 kJ mol−1) and the monovalent cations play a critical role in the single carboxylation of dicarbenes with CO2. In comparison, divalent alkali earth metal cations, due to both their smaller sizes and higher formal charges, exhibit a much stronger influence (ΔBE > 100 kJ mol−1). Divalent cations should be incorporated into next generation CO2 capture reagents. Other aspects including the reaction potential energy surface (PES), orbital-based analyses of interactions, substitution effects, and the reactivity descriptors (cation size, reacting N lone pair orbital energy, etc.) have been discussed in detail as well.

A novel 2D structure composed only of carbon and nitrogen elements at the molar ratio of 1:1 is predicted by first-principles calculations. The basic structural units are 1,3,5-triazine molecules which trimerize and polymerize into a 2D network of semiconductor nature. Six triazine units comprise a hollow hexagon with a van der Waals hole diameter of about 2.4 Å, which is suitable for H2 separation from larger molecules. Metal atoms of various sizes can strongly bind over the polynitrogen pore, which suggests that the 2D network is an ideal support for single-atom catalysis.

The oxidation of CO on strained Pt(100) surface was studied using periodic density functional theory (DFT). Unlike the uniform response of global properties (e.g., d-band center) to strain, the localized nature of adsorption leads to complex site-dependent and adsorbate-dependent responses, invalidating the generally believed statement of “tension strengthens binding”. Moreover, the complex responses of reaction energetics to strain require direct study of the reaction under strain rather than extrapolating the known behaviors of individual adsorbates under strain or reaction energetics on unstrained surfaces. We show that the tensile strain lowers the reaction barrier of CO oxidation over the Pt(100) surface. This work provides a theoretical basis of utilizing strain to improve the Pt catalysts with a higher tolerance toward CO poisoning.

Synthesis of anisotropic nanostructures from materials with isotropic crystal structures often requires the use of seeds containing twin planes to break the crystalline symmetry and promote the preferential anisotropic growth. Controlling twinning in seeds is therefore critically important for high-yield synthesis of many anisotropic nanostructures. Here, we demonstrate a unique strategy to induce twinning in metal nanostructures for anisotropic growth by taking advantage of the large lattice mismatch between two metals. By using Au–Cu as an example, we show, both theoretically and experimentally, that deposition of Cu to the surface of single-crystalline Au seeds can build up strain energy, which effectively induces the formation of twin planes. Subsequent seeded growth allows the production of Cu nanorods with high shape anisotropy that is unachievable without the use of Au seeds. This work provides an effective strategy for the preparation of anisotropic metal nanostructures.Keywords: copper; core−shell; epitaxial growth; gold; lattice mismatch; twinned structure;

An example of using readily available, less reactive aryl bromides as arylating reagents in the Pd(II)-catalyzed intermolecular arylation of unactivated C(sp3)–H bonds is described. This reaction was promoted by a crucial 8-aminoquinolinyl directing group and a K2CO3 base, enabling regiospecific installation of an aryl scaffold at the β-position of carboxamides. A mechanistic study by DFT calculations reveals a C(sp3)–H activation-led pathway featuring the oxidative addition as the highest energy transition state.

Allylic rearrangement or the migration of a double bond from its original position in the carbon skeleton to an adjacent site was observed when 3,4,5,6-tetrahydrophthalate was hydrolyzed in a basic solution and in the presence of Co(II) and Mn(II) under hydrothermal conditions.

Arynes are shown to insert into some C═X double bonds, leading to benzannulated four-membered rings. The strain of these rings allow for a ready, spontaneous opening to afford o-quinomethide analogues. Subsequent nucleophilic addition re-aromatizes the intermediates to achieve ortho-difunctionalization of arynes. In this report, we describe the aryne insertion into the C═C double bonds of vinylogous amides and the C═N double bonds of carbodiimides. The correlation and comparison with aryne single bond insertion chemistry will be discussed. Computational studies for the ring-opening step, as well as the nature of the o-quinomethide intermediates, will also be discussed.

We report here that mono-N-protected amino acids (MPAAs), an important environmentally compatible structural motif, enable acceleration of Pd(II)-catalyzed dehydrogenative Heck reactions between pyridines and electron-deficient arenes with simple alkenes, leading to diversely functionalized C3- or meta-selective alkenylated pyridines and benzenes via non-chelate-assisted C–H activation. A comprehensive theoretical study by DFT calculations discloses that the amino scaffold of the MPAA ligand facilely converts to an X-type ligand by an initial N–H activation, resulting in a relatively low activation barrier for the C–H cleavage of pyridine. Then a property reversal of the amino group from X-type to L-type ligand allows the alkene substitution to take place smoothly, while the carboxyl group enables the formation of an intramolecular hydrogen bond, significantly decreasing the activation barrier for the carbopalladation. The results of calculations and the kinetic isotopic effect measurement support a rate-limiting C–H activation by a mechanism involving a concerted metalation/deprotonation pathway, with an endothermicity of 31.0 kcal/mol in the process.

Cation-assisted interactions between N-containing heterocycles (NHCs) and CO2 have been systematically studied by using density functional theory (DFT). For neutral and anionic (non-carbenoid) NHCs, the effects of monovalent cations (i.e., alkali metal ions) are moderate to small (the NHC–CO2 binding energy change, ΔBE usually < 25 kJ mol−1). However, for NHC carbenes, due to their strong basicity, the effects are strong (ΔBE > 60 kJ mol−1) and the monovalent cations play a critical role in the single carboxylation of dicarbenes with CO2. In comparison, divalent alkali earth metal cations, due to both their smaller sizes and higher formal charges, exhibit a much stronger influence (ΔBE > 100 kJ mol−1). Divalent cations should be incorporated into next generation CO2 capture reagents. Other aspects including the reaction potential energy surface (PES), orbital-based analyses of interactions, substitution effects, and the reactivity descriptors (cation size, reacting N lone pair orbital energy, etc.) have been discussed in detail as well.

Allylic rearrangement or the migration of a double bond from its original position in the carbon skeleton to an adjacent site was observed when 3,4,5,6-tetrahydrophthalate was hydrolyzed in a basic solution and in the presence of Co(II) and Mn(II) under hydrothermal conditions.