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Molybdenum diselenide (MoSe2) has been considered as promising electrocatalysts for catalyzing the hydrogen evolution reaction (HER) due to its narrow band gap and appropriate adsorption free energy. However, its catalytic performance is still impeded by inferior electrical conductivity and insufficient active sites, thus leading to unsatisfactory HER performance. Herein, MoSe2@N-doped carbon (NC) hollow nanoflowers with interfacial Mo-N-C bonds were controllably fabricated through the in situ selenization of the self-polymerized Mo-polydopamine precursor. Benefiting from the unique hollow structure, NC protective layer, and intimate interfacial interaction, the optimal MoSe2@NC displays good HER performance with low overpotentials (175 and 183 mV) and long-term stability (up to 12 h at -10 mA cm-2) in 0.5 M H2SO4 and 1.0 M KOH solutions, respectively. The theoretical results show that Mo-N-C bonds at the interface of MoSe2@NC give rise to relatively low unoccupied eg orbital density of states and ideal H2 adsorption free energy. This work presented here highlights the critical role of interfacial chemical bonds in regulating the electronic structure of nanomaterials and further improving the HER performance.

Three novel porous transition-metal-organic frameworks (TM-OFs), formulated as [Co

Eight new stable porous lanthanide metal-organic frameworks (Ln-OFs), namely, [Ln

Molybdenum diselenide (MoSe

The assembly of a fluorescent dicarboxylate ligand with a barium ion resulted in the formation of a 3D metal-organic framework, Ba5(ADDA)5(EtOH)2(H2O)3·5DMF (UPC-17), based on a 1D rod-shaped secondary building unit. The unprecedented solvent-dependent sensitivities of UPC-17 for the detection of Fe(3+)/Al(3+) ions and 4-nitrophenol with high efficiency were observed for the first time. Significantly, UPC-17 exhibits superior "turn-off" detection for the Fe(3+) ion in methanol and acetone emulsions but shows "turn-on" detection in tetrahydrofuran emulsion. Furthermore, the visible color changes in the detection process make them easy to distinguish by the naked eye, which further increases its application potential.

Two amino-functional copper metal-organic frameworks of formula [Cu3(ATTCA)2(H2O)3]·2DMF·11H2O·12EtOH (1) (H3ATTCA = 2-amino-[1,1:3,1-terphenyl]-4,4,5-tricarboxylic acid, pyz = pyrazine, DMF = dimethylformamide) and [Cu3(ATTCA)2(pyz)(H2O)]·2DMF·12H2O·8EtOH (2) were synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analyses, thermogravimetric analyses, and powder X-ray diffraction. Single-crystal X-ray diffraction analysis revealed that both complexes 1 and 2 are built of the Cu2(COO)4 paddlewheel secondary building units with an fmj topology. Importantly, complex 1 can be transformed into complex 2 by the single-crystal to single-crystal transformation of which the coordinated water molecules are replaced with pyz molecules. However, the adsorption abilities of 2 are obviously lower than those of 1, as its pores are partially blocked by pyz molecules. Moreover, gas-adsorption analysis showed that the amino-functional 1 possesses higher gas-adsorption capacity than UMCM-151 for N2, H2, CH4, and C2H2, especially for CO2.

To assemble metal-organic supramolecules such as a metallamacrocycle and metal-organic coordination cage (MOCC), a series of flexible dicarboxylate ligands with the appropriate angle, 2,2'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(1)), 2,2'-(2,5-dimethyl-1,4-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(2)), 2,2'-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)bis(sulfanediyl)dinicotinic acid (H(2)L(3)), and 2,2'-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(4)), have been designed and synthesized. Using these flexible ligands to assemble with metal ions, six metal-organic supramolecules, Cd(2)(L(1))(2)(dmf)(4)(H(2)O)(2).H(2)O (1), Mn(3)((1)L(2))(2)((2)L(2))(dmf)(2)(H(2)O)(2).5dmf (2), Cu(4)(L(3))(4)(H(2)O)(4).3dmf (3), Cu(4)(L(4))(4)(dmf)(2)(EtOH)(2).8dmf.6H(2)O (4), Mn(4)(L(4))(4)(dmf)(4)(H(2)O)(4).6dmf.H(2)O (5), and Mn(3)(L(4))(3)(dmf)(4).2dmf.3H(2)O (6), possessing a rectangular macrocycle, MOCCs or their extensions, and 1D or 2D coordination polymers, have been isolated. All complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, and thermogravimetric analysis. Complex 1 is a discrete rectangular macrocycle, while complex 2 is a 2D macrocycle-based coordination polymer in which the L(2) ligand adopts both syn and anti conformations. Complexes 3-5 are discrete MOCCs in which two binuclear metal clusters are engaged by four organic ligands. The different geometries of the secondary building units (SBUs) and the axial coordinated solvates on the SBUs result in their different symmetries. Complex 6 is a 1D coordination polymer, extended from a MOCC made up of two metal ions and three L(4) ligands. All of the flexible dicarboxylate ligands adopt a syn conformation except that in complex 2, indicating that the syn conformational ligand is helpful for the formation of a metallamacrocycle and a MOCC. The magnetic properties of complexes 5 and 6 have also been studied.

A three-dimensional porous Zn metal-organic framework (UPC-12) with high thermal and chemical stability was isolated in high yield and purity from a hydrothermal reaction. UPC-12 exhibits high selectivity for CO2 due to the formation of hydrogen bonds between CO2 molecules and the -COOH groups exposed inside the channels and the effective π-π interactions between CO2 molecules and the pillared bipyridine moieties of the MOF. The adsorption-desorption process was studied, for the first time, by both (13)C CP-TOSS NMR spectroscopy and in situ DRIFTS.

Two 3D noninterpenetrating porous metal-organic frameworks (PMOFs) [Cd3(L(1))2(DMA)2]·DMA [1, H3L(1) = tris(p-carboxylic acid)tridurylborane] and [Zn3(L(2))3(H2O)2]·5H2O·2EtOH [2, H2L(2) = 4,4'-((2,3,5,6-tetramethylphenyl)boranediyl)bis(2,3,5,6-tetramethylbenzoic acid)] were synthesized by employment of a C3-symmetric ligand (H3L(1)) to assembly with Cd(NO3)2 or Zn(NO3)2. Complex 1 exhibits a (3, 6)-connected topological network based on a Cd3 cluster and Y-shaped trinodal organic linker. Complex 2 shows a 6-connected topology, since in situ decarboxylic reaction of the initial H3L(1) occurred to generate a new ligand, H2L(2), which can be considered as a linear linker. Both 1 and 2 exhibit blue fluorescence. Significantly, complex 1 with larger channels is unstable upon the removal of guest molecules. In contrast, activated 2 exhibits higher stability and permanent porosity.

Zinc paddlewheel metal-organic frameworks (MOFs) frequently exhibit low stability or complete collapse upon the removal of axial ligands. Hence, there are very few reports on gas adsorption of zinc paddlewheel MOFs. In this work, the N2 and H2 adsorption measurements were carried out for a zinc MOF (namely, SDU-1) based on two types of paddlewheel secondary building units (SBUs): [Zn2(COO)3] and [Zn2(COO)4]. Because of the existence of inherent surface instability upon removal of solvates in zinc paddlewheel SBU, SDU-1 possesses a very low surface area. Through metal-ion metathesis in a single-crystal-to-single-crystal fashion, the Zn(2+) ions in SDU-1 were exchanged by Cu(2+) ions to generate Cu-SDU-1. Through the measurements of gas adsorption and catalytic test, the porosity and catalytic capacity of Cu-SDU-1 have been improved significantly, compared to SDU-1.

A new porous zirconium metal–organic framework (Zr MOF), Zr6(μ3-O)4(μ3-OH)4(OH)6(H2O)6(BTB)2·6DMF·H2O (1; H3BTB = 5′-(4-carboxyphenyl)[1,1′:3′,1″-terphenyl]-4,4″-dicarboxylic acid), based on Zr6 clusters and tricarboxylate ligands has been constructed and characterized. The Zr6 clusters were linked by BTB ligands to generate a 2D network of kgd topology. The interpenetrations among the 2D networks gave rise to a 3D porous framework, which represents the first Zr MOF constructed from 2D → 3D interpenetration. The gas uptake and catalytic properties for 1 have also been studied.

By application of mixed organic ligands of 5-amino-2,4,6-triiodoisophthalic acid (H(2)ATIBDC) and 4,4'-bipyridine (bpy) to assemble with Zn ions at room temperature, two novel polymorphic structures, Zn(ATIBDC)(bpy).3H(2)O (denoted as MONT-1 and MONT-2), possessing one-dimensional metal-organic nanotubular structures have been synthesized and characterized. MONT-1 was generated by connection of the zero-dimensional Zn-bpy squares through the bridging ATIBDC ligands, while MONT-2 was formed by connection of the one-dimensional Zn-bpy helix through the ATIBDC ligands. Both nanotubes possess highly crystalline stabilities and can absorb the uncoordinated water molecules reversibly.

The solvothermal reaction of Zn(NO(3))(2)·6H(2)O and 4,4',4''-(2,4,6-trimethylbenzene-1,3,5-triyl)tribenzoic acid (H(3)TMTA) in N,N'-diethylformamide or N,N-dimethylacetamide gave rise to two layered honeycomb frameworks. The different stacking arrangements of the 2D layers generate achiral (α-1) and chiral (β-1) architectures, which are supramolecular isomers. The homochiral crystallization of β-1 can be achieved through chiral inducement, which is confirmed by circular dichroism spectra.

By application of a newly developed C(3)-symmetric tripodal carboxylate ligand, 1,1',1''-(benzene-1,3,5-triyl)tripiperidine-4-carboxylic acid (H(3)BTPCA) to assemble with zinc ion in the presence of pyridine, a novel 2-fold interpenetrating polyhedral metal-organic framework with a primitive cubic network based on supermolecular building blocks (SBBs) has been synthesized. The basic paddlewheel secondary building units (SBUs) are connected by deprotonated BTPCA ligands to generate an octahedron as the SBB, which is further connected through the six vertexes by sharing the paddlewheel SBUs to give rise to the 3D primitive cubic network.