Zhaoxu Wang

Porous NbO-type metal–organic framework with inserted acylamide groups exhibiting highly selective CO2 capture

A new expanded microporous NbO-type metal–organic framework [Cu2(BDPT4−)]n with inserted acylamide groups has been designed and synthesized, which shows both a large CO2-uptake capacity (156.4 cm3 g−1 at 1 bar) and a high selectivity for CO2 over N2 (39.8) and CH4 (7.2) at 273 K.

Enhanced water stability of a microporous acylamide-functionalized metal–organic framework via interpenetration and methyl decoration

A microporous acylamide-functionalized MOF with a 2-fold interpenetrated and methyl decorated framework (HNUST-4) has been designed and synthesized from [Cu2(COO)4] motifs and a C2-symmetric acylamide-linking tetracarboxylate, which exhibits good water stability, permanent porosity as well as high and selective CO2 uptake at ambient temperature.

COOPERATIVITY BETWEEN HYDROGEN BOND AND HALOGEN BOND IN HBr⋯BrX⋯HBr (X = F, Cl, Br)

An ab initio study has been carried out to investigate the structures, binding energies and atomic charge of the binary complexes HBr⋯BrX and ternary complexes HBr⋯BrX⋯HBr (X = F, Cl, Br) at the MP2/aug-cc-pvdz theoretical level. Four types of interactions are observed among these systems: hydrogen bond, halogen bond, unusual hydrogen bond and unusual halogen bond. Two types of stable structures existed in the trimers: acyclic and monocyclic. The stabilities of the complexes may be decided by three factors: the strength of the halogen bond, the nature of halogen or hydrogen bond of intermolecular interaction and the type of the trimers structure. The absolute value of the cooperativity contribution in these triads is in range of 0.77 ∼ 21.59%, which shows that the cooperative energy is of importance in them. The nature of the intermolecular interactions has been also investigated through the electrostatic potential and the theory of atoms in molecules (AIM). The values of ∇2ρ at BCPs are positive in all complexes, indicating that the interactions are closed-shell. The ratio |Vc|∕Gc of all complexes ranges from 0.782 to 0.935 (satisfy the condition |Vc|∕Gc 0, revealing that these complexes are predominantly electrostatic in character.

Theoretical investigation on the interplay of hydrogen bond and halogen bond in HX⋯(BrCl)n (X = F, Cl, Br and n = 1, 2) complexes

Quantum chemical calculations at the MP2 level with the aug-cc-pVTZ basis set were used to investigate the HX⋯(BrCl)n (X = F, Cl, Br and n = 1, 2) complexes. They are connected via hydrogen bond or halogen bond in dimers and together in trimers. Molecular geometries, interaction energies, cooperative energies and atomic charge of dyads and triads have been studied at the Mp2/aug-cc-pVTZ computational level. All studied trimers show cooperativity with the simultaneous presence of a hydrogen and one or two halogen bond. The molecular electrostatic potential has been employed to explore the formation mechanisms of these molecular complexes. The AIM analysis has been performed at the Mp2/aug-cc-pVTZ level to examine the topological characteristics, confirming the coexistence of hydrogen bonds and one or two halogen bond for each complex.

A highly porous acylamide decorated MOF-505 analogue exhibiting high and selective CO2 gas uptake capability

Porous metal–organic frameworks (MOFs) constructed from organic linkers and metal ions/clusters can provide special pore environments for selective CO2 capture. In this work, we designed and synthesized a highly porous acylamide-functionalized MOF (HNUST-7) from a nanosized linear diisophthalate ligand with linking acylamide groups and Cu(II)-paddlewheel clusters. Structural analysis shows that HNUST-7 possesses a (4,4)-connected NbO-type 3D open framework incorporating two different types of metal–organic cages. After activation, HNUST-7 displays a high BET surface area of 2804 m2 g−1 and large CO2 uptakes of 26.1 and 19.4 mmol g−1 under 30 bar at 273 and 298 K, respectively. In addition, with the optimized pores and functional sites (open copper sites and Lewis basic acylamide groups) integrated within the framework, HNUST-7 exhibits highly selective adsorption of CO2 over CH4 and N2 under ambient conditions, which have been verified by both single compound gas sorption measurements and dynamic column breakthrough experiments.

Insight into Capture of Greenhouse Gas (CO2) based on Guanidinium Ionic Liquids

Quantum mechanics and molecular dynamics are used to simulate guanidinium ionic liquids. Results show that the stronger interaction exists between guanidine cation and chlorine anion with interaction energy about 109.216 kcal/mol. There are two types of spatial distribution for the title system: middle and top. Middle mode is a more stable conformation according to energy and geometric distribution. It is also verified by radial distribution function. The continuous increase of carbon dioxide (CO2) does not affect the structure of ionic liquids, but CO2 molecules are always captured by the cavity of ionic liquids.

Cooperative effects between F … Ag bonded and X … Br (Cl) halogen-bonded interaction in BrF(ClF) … AgX … BrF(ClF) (X = F, Cl, Br) complexes: a theoretical study

The equilibrium structures, interaction energies and binding properties of ternary BrF(ClF) …  AgX … BrF(ClF)(X = F, Cl, Br) complexes and the corresponding binary systems have been studied by DFT method at the X3LYP/aug-cc-pVQZ level. Cooperative effects are probed by analysing charge transfer, electronic properties and orbital interactions when F … Ag bond and X … Br (Cl) halogen bond coexist in the same complex. The results indicate that the X … Br (Cl) halogen bond has a greater enhancing effect than the F … Ag bond does, resulting in a shorter binding distances, larger interaction energies and greater electron densities for the ternary complexes than for the corresponding binary ones. In addition, the origins of both the F … Ag bond and X … Br (Cl) halogen bond have been deduced via energy decomposition. GRAPHICAL ABSTRACT

A theoretical investigation on Cu/Ag/Au bonding in XH2P⋯MY(X = H, CH3, F, CN, NO2; M = Cu, Ag, Au; Y = F, Cl, Br, I) complexes

Intermolecular interaction of XH2P···MY (X = H, CH3, F, CN, NO2; M = Cu, Ag, Au; Y = F, Cl, Br, I) complexes was investigated by means of an ab initio method. The molecular interaction energies are in the order Ag < Cu < Au and increased with the decrease of RP···M. Interaction energies are strengthened when electron-donating substituents X connected to XH2P, while electron-withdrawing substituents produce the opposite effect. The strongest P···M bond was found in CH3H2P···AuF with -70.95 kcal/mol, while the weakest one was found in NO2H2P···AgI with -20.45 kcal/mol. The three-center/four-electron (3c/4e) resonance-type of P:-M-:Y hyperbond was recognized by the natural resonance theory and the natural bond orbital analysis. The competition of P:M-Y ↔ P-M:Y resonance structures mainly arises from hyperconjugation interactions; the bond order of bP-M and bM-Y is in line with the conservation of the idealized relationship bP-M + bM-Y ≈ 1. In all MF-containing complexes, P-M:F resonance accounted for a larger proportion which leads to the covalent characters for partial ionicity of MF. The interaction energies of these Cu/Ag/Au complexes are basically above the characteristic values of the halogen-bond complexes and close to the observed strong hydrogen bonds in ionic hydrogen-bonded species.

An unprecedented water stable acylamide-functionalized metal–organic framework for highly efficient CH4/CO2 gas storage/separation and acid–base cooperative catalytic activity

The high porosity, excellent water stability and optimized supramolecular host–guest interactions of MOFs are the three key factors for their potential practical applications in many important areas including gas storage/separation, catalysis and so on. In this study, we designed and constructed a highly porous (3, 36)-connected txt-type acylamide-functionalized metal–organic framework (HNUST-8) from a pyridine-based acylamide-linking diisophthalate and dicopper(II)-paddlewheel clusters. Interestingly, HNUST-8 possesses an exceptionally water-stable framework with a high BET surface area of about 2800 m2 g−1. At 298 K, HNUST-8 exhibits a high excess CO2 uptake of 19.7 mmol g−1 at 40 bar, an excellent total CH4 storage capacity of 223 cm3(STP) cm−3 with a large working capacity of 178 cm3(STP) cm−3 at 80 bar, as well as highly efficient CO2/CH4 and CO2/N2 separation under dynamic conditions at 1 bar. Moreover, with the Lewis acidic open copper(II) sites and Lewis basic acylamide groups integrated into the framework, HNUST-8 demonstrates efficient catalytic activity as an acid–base cooperative catalyst in a tandem one-pot deacetalization–Knoevenagel condensation reaction.