Presented in this article are the anion-tuning formation, crystal structures and luminescent properties of four coordination polymers of N,N′-di(3-pyridine) oxamide (DPOM), including two ...one-dimensional (1D) chain/ladder polymers, Ni(DPOM)(H2O)4SO4·2H2O (1) and Cd4(DPOM)6(NO3)8 (2), as well as two 3D coordination polymers, Zn2(DPOM)(H2O)4(SO4)2 (3) and Cd2(DPOM)(H2O)4(SO4)2 (4). The results of single crystal X–ray diffraction analyses indicate that in these coordination polymers, DPOM ligand serves as a bridge, connecting metal ions by both terminal pyridine N atoms. 1 is a 1D chain structure formed by the bridge of DPOM. 2 is a 1D ladder-like structure featuring Cd(NO3)2 structural units bridged by DPOM ligands. Both 3 and 4 are 3D pillar-layer structures with the 2D inorganic layer ZnSO4/CdSO4 pillared by DPOM ligands. The results of photoluminescent measurements illustrate that upon excitation, 2–4 can emit fluorescence in 408, 416, and 422nm in the solid state, respectively.
Reported in this article are the crystal structures and luminescent properties of four coordination polymers of N,N′-di(3-pyridine) oxamide ligand prepared by anion-tuning approach. Display omitted
•Four coordination polymers have been constructed by anion-tuning.•Their structures have been determined by X-ray diffraction.•They are potential luminescent materials.
A 3D microporous cadmium(II) metal-organic framework based on 1H-tetrazole exhibits strong hydrogen binding with an initial enthalpy of adsorption of 13.3 kJ/mol, due to the smaller pore sizes and ...the high hydrogen binding affinity of the tetrazolyl-ring-decorated inner surface of the pores.
The solar-driven CO
reduction is a challenge in the field of "artificial photosynthesis", as most catalysts display low activity and selectivity for CO
reduction in water-containing reaction systems ...as a result of competitive proton reduction. Herein, we report a dinuclear heterometallic complex, CoZn(OH)L
(ClO
)
(CoZn), which shows extremely high photocatalytic activity and selectivity for CO
reduction in water/acetonitrile solution. It achieves a selectivity of 98 % for CO
-to-CO conversion, with TON and TOF values of 65000 and 1.8 s
, respectively, 4, 19, and 45-fold higher than the values of corresponding dinuclear homometallic CoCo(OH)L
(ClO
)
(CoCo), ZnZn(OH)L
(ClO
)
(ZnZn), and mononuclear CoL
(CH
CN)(ClO
)
(Co), respectively, under the same conditions. The increased photocatalytic performance of CoZn is due to the enhanced dinuclear metal synergistic catalysis (DMSC) effect between Zn
and Co
, which dramatically lowers the activation barriers of both transition states of CO
reduction.
Five three‐dimensional (3D) coordination polymers, {(NiL)(NiL)(V16O42)}n·2nH2O (1), (NiL)3(VO3)6n·5nH2O (2), (NiL)3(V6O18)n·7nH2O (3), (NiL)3(V8O23)n (4), and (NiL)4(V10O29)n (5), have been obtained ...by the reaction of the macrocyclic nickel complex NiL(ClO4)2 (L = 1,4,8,11‐tetraazacyclotetradecane) with NH4VO3 under different conditions. Single‐crystal X‐ray diffraction analyses revealed that the VO3– anion assumes diverse species and structures in these five coordination polymers, including the V16O42n4n– sheet, V6O186– ring, VO3nn– chain, VO3nn– sheet, and V10O29n8n– chain. The V16O42n4n– sheets, V6O186– rings, VO3nn– chains, VO3nn– sheets, and V10O29n8n– chains are linked together through NiL2+ bridges to form the 3D frameworks of 1–5. The single‐crystal to single‐crystal transformation between 2 and desolvated 2 was successfully realized. Electrochemical measurements indicate that 2 and 4 are potential catalysts for water splitting.
Five coordination polymers have been constructed from a macrocyclic NiII complex and vanadium polyoxoanions. The vanadium polyoxoanions assume diverse structures, namely the V16O42n4n– sheet, V6O186– ring, VO3nn– chain, VO3nn– sheet, and V10O29n8n– chain. Electrochemical measurements indicate that two of the coordination polymers are potential catalysts for water splitting.
The mismatched fast‐electron‐slow‐proton process in the electrocatalytic oxygen evolution reaction (OER) severely restricts the catalytic efficiency. To overcome these issues, accelerating the proton ...transfer and elucidating the kinetic mechanism are highly sought after. Herein, inspired by photosystem II, we develop a family of OER electrocatalysts with FeO6/NiO6 units and carboxylate anions (TA2−) in the first and second coordination sphere, respectively. Benefiting from the synergistic effect of the metal units and TA2−, the optimized catalyst delivers superior activity with a low overpotential of 270 mV at 200 mA cm−2 and excellent cycling stability over 300 h. A proton‐transfer‐promotion mechanism is proposed by in situ Raman, catalytic tests, and theoretical calculations. The TA2− (proton acceptor) can mediate proton transfer pathways by preferentially accepting protons, which optimizes the O−H adsorption/activation process and reduces the kinetic barrier for O−O bond formation.
We developed an electrocatalytic model that is designed to obtain superior oxygen evolution reaction activity (270 mV at 200 mA cm−2) and cycle stability (over 300 h) by tuning the proton transfer pathway. The electron‐rich terephthalic acid anion located in the second coordination sphere of the active center can mediate proton transfer pathways by preferentially accepting protons, which reduces the kinetic barrier for O−O bond formation.
Synergistic catalytic effects aid the photocatalytic reduction of CO2 to CO by a dinuclear cobalt cryptate complex in CH3CN/H2O solution. In their Communication on page 738 ff., D. C. Zhong, T. B. ...Lu, and co‐workers demonstrate that one CoII unit serves as a catalytic center and the other CoII unit acts as an assistant catalytic site to facilitate the cleavage of the C−O bond of the O=C−OH intermediate, thus leading to a higher catalytic activity than for the corresponding mononuclear CoII complex.
A dinuclear cobalt complex Co
(OH)L
(ClO
)
(1, L
=N(CH
)
NHCH
(m-C
H
)CH
NH(CH
)
N) displays high selectivity and efficiency for the photocatalytic reduction of CO
to CO in CH
CN/H
O (v/v=4:1) under ...a 450 nm LED light irradiation, with a light intensity of 100 mW cm
. The selectivity reaches as high as 98 %, and the turnover numbers (TON) and turnover frequencies (TOF) reach as high as 16896 and 0.47 s
, respectively, with the calculated quantum yield of 0.04 %. Such high activity can be attributed to the synergistic catalysis effect between two Co
ions within 1, which is strongly supported by the results of control experiments and DFT calculations.
Covalent organic frameworks (COFs) have been widely studied in photocatalytic CO2 reduction reaction (CO2RR). However, pristine COFs usually exhibit low catalytic efficiency owing to the fast ...recombination of photogenerated electrons and holes. In this study, we fabricated a stable COF‐based composite (GO‐COF‐366‐Co) by covalently anchoring COF‐366‐Co on the surface of graphene oxide (GO) for the photocatalytic CO2 reduction. Interestingly, in absolute acetonitrile (CH3CN), GO‐COF‐366‐Co shows a high selectivity of 94.4 % for the photoreduction of CO2 to formate, with a formate yield of 15.8 mmol/g, which is approximately four times higher than that using the pristine COF‐366‐Co. By contrast, in CH3CN/H2O (v : v=4 : 1), the main product for the photocatalytic CO2 reduction over GO‐COF‐366‐Co is CO (96.1 %), with a CO yield as high as 52.2 mmol/g, which is also approximately four times higher than that using the pristine COF‐366‐Co. Photoelectrochemical experiments demonstrate the covalent bonding of COF‐366‐Co and GO to form the GO‐COF‐366‐Co composite facilitates charge separation and transfer significantly, thereby accounting for the enhanced catalytic activity. In addition, theoretical calculations and in situ Fourier transform infrared spectroscopy reveal H2O can stabilize the *COOH intermediate to further form a *CO intermediate via O−H(aq)⋅⋅⋅O(*COOH) hydrogen bonding, thus explaining the regulated photocatalytic performance.
The photocatalytic performance for the reduction of CO2 to HCOO− or CO can be significantly enhanced by covalently anchoring COF‐366‐Co on the surface of graphene oxide.
A catalyst developed from a Cu
complex of (Et
N)Cu(pyN
)(HCO
)⋅0.5 CH
OH⋅H
O (1⋅0.5 CH
OH⋅H
O; pyN
=bis(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate(2-)) shows a high activity to catalyze the ...reduction reaction of CO
to CO driven by visible light in 4:1 acetonitrile/water (v:v) using Ru(phen)
(PF
)
as photosensitizer and TEOA as sacrificial reductant, with a high TON of 9900 and a high CO selectivity of 98 %. The results of isotope labeling experiment, durability tests and energy dispersive spectroscopy reveal that 1 is robust during the photocatalytic process.
The gelation ability of melamine was evaluated under various acidic conditions, and the related gelator aggregates were investigated with scanning electron microscopy, transmission electron ...microscopy, single-crystal X-ray diffraction, thermo-gravimetric analysis, differential scanning calorimetric analysis, rheological experiments, 1 H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and powder X-ray diffraction. It was found that melamine interacted strongly with a number of organic/inorganic acids in water, forming thermal-reversible supramolecular hydrogels with different critical gelator concentrations (CGCs). The CGCs of gelators successively made with salicylic acid, m -hydroxybenzoic acid and p -hydroxybenzoic acid decreased because of the steric hindrance, whereas those related to oxalic acid dihydrate and orthoboric acid presented higher values due to the lack of a phenyl ring in the molecular structures. More interestingly, a unique onium salt, 2,4,6-triamino-1,3,5-triazin-1-ium benzoate dihydrate (TTIBD), was formed via the Lewis acid–base reaction of benzoic acid and melamine. It crystallized in the monoclinic space group C 2/ c ( Z = 8) with lattice parameters a = 21.477 (3) Å, b = 10.2253 (14) Å, c = 12.3312 (17) Å and β = 98.717 (3)°. The formed hydrogel not only exhibited thermo-sensitive characteristics and solid-like behavior, but also showed a solution–gel–crystal transition, being an amorphous-to-crystalline phase transition. By increasing the concentration from 0.04 to 0.12 mol L −1 , the gel–solution transition temperature increased from 23.0 to 49.5 °C, and the gel–crystal transition time decreased from 430 to 253 min, but both leveled off upon increasing the concentration. The TTIBD crystal along with the corresponding hydrogel was self-assembled via hydrogen bonds and π–π stacking interactions.
PDF
