Dong-Dong Zhou

Strong and Dynamic CO2 Sorption in a Flexible Porous Framework Possessing Guest Chelating Claws

Using a bis-triazolate ligand and tetrahedral Zn(II) ion, we synthesized a flexible porous coordination polymer functionalized with pairs of uncoordinated triazolate N-donors that can be used as guest chelating sites to give very high CO(2) adsorption enthalpy and CO(2)/N(2) selectivity. The dynamic CO(2) sorption behavior could be monitored well by single-crystal X-ray diffraction.

Monodentate hydroxide as a super strong yet reversible active site for CO2 capture from high-humidity flue gas

We demonstrate here that porous coordination frameworks, functionalized with monodentate hydroxide on the pore surface, can achieve ultrahigh CO2 adsorption affinity (124 kJ mol−1), adsorption capacity (9.1 mmol cm−3 at 298 K and 1 bar), and CO2/N2 selectivity (262 at 298 K) by the reversible formation/decomposition of bicarbonate in the adsorption/desorption processes. More importantly, these materials can capture up to 4.1 mmol cm−3 or 13.4 wt% of CO2 from simulated flue gases (CO2 pressure 0.10–0.15 bar at 313 K) even at high relative humidity (82%) and quickly release it under mild regeneration conditions (N2 purge at 358 K), representing the best CO2 capture performances reported to date.

Modular and Stepwise Synthesis of a Hybrid Metal–Organic Framework for Efficient Electrocatalytic Oxygen Evolution

The paddle-wheel type cluster Co2(RCOO)4(LT)2 (R = substituent group, LT = terminal ligand), possessing unusual metal coordination geometry compared with other cobalt compounds, may display high catalytic activity but is highly unstable especially in water. Here, we show that with judicious considerations of the host/guest geometries and modular synthetic strategies, the labile dicobalt clusters can be immobilized and stabilized in a metal-organic framework (MOF) as coordinative guests. The Fe(na)4(LT) fragment in the MOF [{Fe3(μ3-O)(bdc)3}4{Fe(na)4(LT)}3] (H2bdc = 1,4-benzenedicaboxylic acid, Hna = nicotinic acid) can be removed to give [{Fe3(μ3-O)(bdc)3}4] with a unique framework connectivity possessing suitable distribution of open metal sites for binding the dicobalt cluster in the form of Co2(na)4(LT)2. After two-step, single-crystal to single-crystal, postsynthetic modifications, a thermal-, water-, and alkaline-stable MOF [{Fe3(μ3-O)(bdc)3}4{Co2(na)4(LT)2}3] containing the desired dicobalt cluster was obtained, giving extraordinarily high electrocatalytic oxygen evolution activity in water at pH = 13 with overpotential as low as 225 mV at 10.0 mA cm-2.

A Metal–Organic Framework with a Pore Size/Shape Suitable for Strong Binding and Close Packing of Methane

Much effort has been devoted to develop new porous structures for methane storage. We report a new porous coordination framework showing exceptional methane uptakes (e.g. 263 v/v at 298 K and 65 bar) and adsorption enthalpies (21.6 kJ mol(-1)) as high as current record holders functionalized by open metal sites. Computational simulations demonstrated that the hierarchical pore structure consisting of single-wall nanocages has suitable sizes/shapes and organic binding sites to enforce not only strong host-methane and methane-methane interactions but also dense packing of methane molecules.

Visualizing the distinctly different crystal-to-crystal structural dynamism and sorption behavior of interpenetration-direction isomeric coordination networks

We show here that the interpenetration direction can be more important than the interpenetration number for the porosity, stability, framework flexibility and sorption behaviors of porous coordination frameworks. Solvothermal reactions of Zn(NO3)2 and a shape-asymmetric ligand 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid (H2mpba) in different solvents/templates gave three isomeric frameworks [Zn(Hmpba)2] (1, 2, 3) possessing the same polar dia networks and 4-fold interpenetration. However, their polar nets adopt parallel, orthogonal, and anti-parallel arrangements, respectively, giving very similar voids but totally different pore shapes for 1 and 2, and a nonporous structure for 3. Thermogravimetry, powder X-ray diffraction, and sorption analyses revealed remarkably different framework flexibilities and multi-step gas sorption behavior, in which 1 selectively adsorbs CO2 over N2, 2 adsorbs both CO2 and N2, while 3 adsorbs neither CO2 nor N2. Although these compounds cannot retain their single-crystallinity after structural transformations and their complicated structures hinder conventional structural characterization techniques, we successfully combined first-principle calculations and computational simulations to solve the crystal structures of their activated phases, and developed a dynamic computational simulation method combining sorption simulated annealing, molecular mechanics and grand canonical Monte Carlo modelling to perfectly simulate the CO2 adsorption/desorption isotherms and visualize the accompanying continuous/abrupt structural transformations, demonstrating the important role of interpenetration-direction isomerism in functional porous materials.

Drastic Enhancement of Catalytic Activity via Post‐oxidation of a Porous MnII Triazolate Framework

Mn(III) is a powerful active site for catalytic oxidation of alkyl aromatics, but it can be only stabilized by macrocyclic chelating ligands such porphyrinates. Herein, by using benzobistriazolate as a rigid bridging ligand, a porous Mn(II) azolate framework with a nitrogen-rich coordinated environment similar to that of metalloporphyrins was synthesized, in which the Mn(II) ions can be post-oxidized to Mn(III) to achieve drastic increase of catalytic (aerobic) oxidation performance.

A novel pillared-layer-type porous coordination polymer featuring three-dimensional pore system and high methane storage capacity

Solvothermal reaction of Zn(NO3)2, 4-(1H-pyrazol-4-yl)pyridine (Hpypz) and 1,3,5-benzenetricarboxylic acid (H3btc) in N,N-dimethylacetamide (DMA) produced a new porous coordination polymer [Zn5(pypz)4(btc)2] (1). Single-crystal X-ray diffraction study of 1 showed that deprotonated pypz– ligands served as 1,2,4-triazolate-like ligands, linking Zn(II) ions to form porous two-dimensional (2-D) sql-a layers {Zn(pypz)}+, which were further connected by eight-legged pillars {Zn2(btc)4(H2O)2}8– based on the typical paddlewheel dinuclear Zn2(RCOO)4(H2O)2 cluster to form a novel type of non-interpenetrated pillared-layer framework with 3-D intersecting pore system and large pore volume. Gas sorption measurements revealed that 1 possesses large BET surface area of 2061 m2 g–1 and very high methane total uptake of 245 cm3(STP) cm–3 at 298 K and 65 bar.

Flexible, Luminescent Metal–Organic Frameworks Showing Synergistic Solid-Solution Effects on Porosity and Sensitivity

Mixing molecular building blocks in the solid solution manner is a valuable strategy to obtain structures and properties in between the isostructural parent metal-organic frameworks (MOFs). We report nonlinear/synergistic solid-solution effects using highly related yet non-isostructural, phosphorescent CuI triazolate frameworks as parent phases. Near the phase boundaries associated with conformational diversity and ligand heterogeneity, the porosity (+150 %) and optical O2 sensitivity (410 times, limit of detection 0.07 ppm) can be drastically improved from the best-performing parent MOFs and even exceeds the records hold by precious-metal complexes (3 ppm) and C70 (0.2 ppm).

Two Novel Ion-Pair Complexes Based on Bis(isomaleonitriledithiolate)nickelate Anion and Substituted Triphenylphosphinium: Syntheses, Weak Interactions, and 3D Structures

Two new Ni(II) complexes, [4RBzTPP]2[Ni(i-mnt)2] (i-mnt = isomaleonitriledithiolate, [4RBzTPP]+ = 1-(4′-R-benzyl)triphenylphosphinium; R = Br(1) and CN(2)), were obtained in the crystalline form by the reaction of K2(i-mnt), NiCl2·6H2O and 1-(4′-R-benzyl)-triphenylphosphinium bromide in H2O. Both complexes crystallize in the triclinic system and the central Ni(II) ion has a distorted square planar coordination. Some weak hydrogen bonds, such as C‒H···S, C‒H···N, or C‒H···Ni, observed between the [Ni(i-mnt)2]2− anion and the cation, play important roles in the stacking of the molecules, and give rise to a 3D network structure.

Two Tetrabromocuprate(II) Salts with Substituted Benzyl Pyridinium: Syntheses, Weak Interactions, Crystal Structures, and Antibacterial Properties

Two tetrabromocuprate (II) salts with substituted benzyl pyridinium, [BzPy]2[CuBr4](1) and [4NO2BzPy]2[CuBr4](2) ([BzPy]+ = 1-benzylpyridinium; [4NO2BzPy]+ = 1-(4′-nitrobenzy- lpyridinium), were synthesized and characterized by elemental analysis, IR, MS, and single-crystal X-ray diffraction. The two salts comprise a [CuBr4]2−anion and two cations, and the [CuBr4]2−anion exhibits a distorted tetrahedral coordination geometry. The weak interactions such as p…π, π…π, C-H…π, C−H…Br or C−H…O hydrogen bonds play important roles in the stacking and stabilization of the two salts, and give rise to a 3D network structure. In addition, the two salts show good antibacterial activities for colibacillus, aurococcus, bacillus subtilus and bacillus thuringiensis.