Ya-Qian Lan

From Metal–Organic Framework to Nanoporous Carbon: Toward a Very High Surface Area and Hydrogen Uptake

In this work, with a zeolite-type metal-organic framework as both a precursor and a template and furfuryl alcohol as a second precursor, nanoporous carbon material has been prepared with an unexpectedly high surface area (3405 m(2)/g, BET method) and considerable hydrogen storage capacity (2.77 wt % at 77 K and 1 atm) as well as good electrochemical properties as an electrode material for electric double layer capacitors. The pore structure and surface area of the resultant carbon materials can be tuned simply by changing the calcination temperature.

Mesoporous Metal‐Organic Frameworks with Size‐tunable Cages: Selective CO2 Uptake, Encapsulation of Ln3+ Cations for Luminescence, and Column‐Chromatographic Dye Separation

Emerging as a new class of porous materials in the last two decades, metal-organic frameworks (MOFs) have been met with great interest owing to their tunable structures and porosities and a wide range of potential applications as functional materials. [ 1 , 2 ] A key feature in MOFs is the porosity, which plays a crucial role in the functional properties, typically in gas/liquid sorption and separation and transport of catalytic substrates/ products. [ 1 , 3 ] The MOFs with tunable pore sizes ranging from non-pores to mesopores are regarded to bridge the gap between zeolites and mesoporous silica. [ 4 ] In recent years much effort has been dedicated to develop MOFs with large and tunable pores, and there are a few mesoporous MOFs reported with various synthetic strategies. [ 1e , 5 ] Increasing the length of bridging ligands has been adopted as a main strategy, but reduced porosity imposed by interpenetration is nevertheless almost unavoidable. [ 6 ] Because of these diffi culties it has been rarely reported to obtain a series of mesoporous MOFs that retain both structure and tunable mesopores upon suppressed interpenetration. To the best of our knowledge, only Schröder, Zhou, and Lin’s groups have constructed a series of mesoporous Cu-/Zn-MOFs with fi xed framework topology but varied pore sizes by systematically varying the length of the bridged ligands, where they have concerned the high gas uptake capabilities or catalytic enantioselectivities, while no selective gas sorption behavior was found for these pore size-tailored MOFs. [ 7 ]

Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution

Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites.

Chiral Nanoporous Metal‐Organic Frameworks with High Porosity as Materials for Drug Delivery

A chiral nanoporous metal-organic framework (MOF) with high porosity is obtained based on nontoxic zinc and achiral hexadentate ligand. It shows high drug loading and slow release of the proportion of the loaded drug with a complete delivery time of about one week when used as a material for adsorption and delivery of anticancer 5-fluorouracil.

A fluorescent sensor for highly selective detection of nitroaromatic explosives based on a 2D, extremely stable, metal-organic framework.

A 2D, extremely stable, metal-organic framework (MOF), NENU-503, was successfully constructed. It displays highly selective and recyclable properties in detection of nitroaromatic explosives as a fluorescent sensor. This is the first MOF that can distinguish between nitroaromatic molecules with different numbers of NO2 groups.

Porous Molybdenum‐Based Hybrid Catalysts for Highly Efficient Hydrogen Evolution

We have synthesized a porous Mo-based composite obtained from a polyoxometalate-based metal-organic framework and graphene oxide (POMOFs/GO) using a simple one-pot method. The MoO2 @PC-RGO hybrid material derived from the POMOFs/GO composite is prepared at a relatively low carbonization temperature, which presents a superior activity for the hydrogen-evolution reaction (HER) in acidic media owing to the synergistic effects among highly dispersive MoO2 particles, phosphorus-doped porous carbon, and RGO substrates. MoO2 @PC-RGO exhibits a very positive onset potential close to that of 20 % Pt/C, low Tafel slope of 41 mV dec(-1) , high exchange current density of 4.8×10(-4)  A cm(-2) , and remarkable long-term cycle stability. It is one of the best high-performance catalysts among the reported nonprecious metal catalysts for HER to date.

N-rich zeolite-like metal–organic framework with sodalite topology: high CO2 uptake, selective gas adsorption and efficient drug delivery

A novel zeolite-like metal–organic framework (ZMOF) with sodalite topology, [Zn(HL)]·DMA (IFMC-1, L = 4,5-di(1H-tetrazol-5-yl)-2H-1,2,3-triazole and IFMC = Institute of Functional Material Chemistry), was solvothermally synthesized based on an N-rich aromatic ligand without a NH2 group. It exhibits high CO2 uptake and selective CO2/N2 adsorption capacity. For the first time, we investigated the influence of a large number of uncoordinated nitrogen atoms from aromatic rings for CO2 adsorption in ZMOFs. This result reveals that the high percentage of open N-donor sites leads to the high uptake capacity for CO2, even in the absence of any NH2 groups and open metal sites. In addition, it also exhibits efficient drug delivery capacity.

Two-Dimensional Tin Selenide Nanostructures for Flexible All-Solid-State Supercapacitors

Due to their unique electronic and optoelectronic properties, tin selenide nanostructures show great promise for applications in energy storage and photovoltaic devices. Despite the great progress that has been achieved, the phase-controlled synthesis of two-dimensional (2D) tin selenide nanostructures remains a challenge, and their use in supercapacitors has not been explored. In this paper, 2D tin selenide nanostructures, including pure SnSe2 nanodisks (NDs), mixed-phase SnSe-SnSe2 NDs, and pure SnSe nanosheets (NSs), have been synthesized by reacting SnCl2 and trioctylphosphine (TOP)-Se with borane-tert-butylamine complex (BTBC) and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone. Utilizing the interplay of TOP and BTBC and changing only the amount of BTBC, the phase-controlled synthesis of 2D tin selenide nanostructures is realized for the first time. Phase-dependent pseudocapacitive behavior is observed for the resulting 2D nanostructures. The specific capacitances of pure SnSe2 NDs (168 F g(-1)) and SnSe NSs (228 F g(-1)) are much higher than those of other reported materials (e.g., graphene-Mn3O4 nanorods and TiN mesoporous spheres); thus, these tin selenide materials were used to fabricate flexible, all-solid-state supercapacitors. Devices fabricated with these two tin selenide materials exhibited high areal capacitances, good cycling stabilities, excellent flexibilities, and desirable mechanical stabilities, which were comparable to or better than those reported recently for other solid-state devices based on graphene and 3D GeSe2 nanostructures. Additionally, the rate capability of the SnSe2 NDs device was much better than that of the SnSe NS device, indicating that SnSe2 NDs are promising active materials for use in high-performance, flexible, all-solid-state supercapacitors.

Self-Assembly and Photocatalytic Properties of Polyoxoniobates: {Nb24O72}, {Nb32O96}, and {K12Nb96O288} Clusters

Three novel polyoxoniobates, KNa(2)[Nb(24)O(72)H(21)]·38H(2)O (1), K(2)Na(2)[Nb(32)O(96)H(28)]·80H(2)O (2), and K(12)[Nb(24)O(72)H(21)](4)·107H(2)O (3) with molecular triangle, molecular square, and cuboctahedral molecular cage geometries, respectively, have been successfully synthesized by conventional aqueous methods. All the compounds are built from [Nb(7)O(22)](9-) fundamental building units. Compound 1 is the first isolated {Nb(24)O(72)} cluster, featuring three heptaniobate clusters linked in a ring by three additional NbO(6) octahedra, while compound 2 is the largest isopolyoxoniobate cluster reported to date, consisting of four heptaniobate clusters linked by four additional NbO(6) octahedra. Compound 3 is the largest solid aggregation of polyoxoniobates, assembled by four {KNb(24)O(72)} clusters joined by four K ions. To our knowledge, it is the first time these polyoxoniobate clusters have been crystallized with only alkali-metal counterions, thereby giving them the possibility of being redissolved in water. ESI-MS spectra indicate that compounds 1 and 2 remain structural integrity when the pure, crystalline polyanion salts are dissolved in water, while compound 3 is partially assembled into Nb(24) fragments. The UV-vis diffuse reflectance spectra of these powder samples indicate that the corresponding well-defined optical absorption associated with E(g) can be assessed at 3.35, 3.17, and 3.34 eV, respectively, revealing the presence of an optical band gap and the nature of semiconductivity with a wide band gap. UV-light photocatalytic H(2) evolution activities were observed for these compounds with Co(III)(dmgH)(2)pyCl as a cocatalyst and TEA as a sacrificial electron donor.

Solvent-Induced Controllable Synthesis, Single-Crystal to Single-Crystal Transformation and Encapsulation of Alq3 for Modulated Luminescence in (4,8)-Connected Metal–Organic Frameworks

In this work, for the first time, we have systematically demonstrated that solvent plays crucial roles in both controllable synthesis of metal-organic frameworks (MOFs) and their structural transformation process. With solvent as the only variable, five new MOFs with different structures have been constructed, in which one MOF undergoes solvent-induced single-crystal to single-crystal (SCSC) transformation that involves not only solvent exchange but also the cleavage and formation of coordination bonds. Particularly, a significant crystallographic change has been realized through an unprecedented three-step SCSC transformation process. Furthermore, we have demonstrated that the obtained MOF could be an excellent host for chromophores such as Alq3 for modulated luminescent properties.