Search

Two scandium coordination polymers (Sc-CPs), [Sc(L1)2(DMF)] (DMF = N,N′-dimethyl formamide, H2L1 = pyrazine-2,3-dicarboxylic acid) (1) and [Sc(L2)(C2O4)0.5(H2O)2]·H2O (H2L2 = pyrazine-2,5-dicarboxylic acid) (2), were prepared via hydrothermal and microwave (MW) heating techniques. It is noted that MW heating can effectively accelerate the reaction compared with a conventional hydrothermal method and decrease the crystal size of the samples. 1 shows a 1D non-planar double chain, while 2 exhibits a brick-like 2D network. After activation, 1 and 2 exhibit good catalytic performance for the cyanosilylation reaction of aromatic aldehydes; in addition, the catalysts prepared by the MW method exhibit better catalytic activity compared with those synthesized by the conventional hydrothermal method.

In our previous work, a family of isostructural lanthanide metal-organic frameworks, [Ln3(L)3(H2O)2]·(H3O)3·(H2O)4·(DMF)3 (abbreviated as Ln3(L)3(H2O)2, Ln = Eu, Tb, Sm, Dy and Gd) were synthesized under solvothermal conditions based on a semi-rigid tetravalent carboxylic tetracarboxylic acid (3,3′,5,5′-biphenyltetracarboxylic acid, H4L). Due to the good sensitization of the H4L ligand, Ln3(L)3(H2O)2 all show the intense characteristic emission bands of the corresponding lanthanide ions. The optical properties of Ln3(L)3(H2O)2 can be easily tuned by doping different lanthanide ions into the same host frameworks. Moreover, white-light emission can be successfully realized for four kinds of codoped compounds Tb0.005Eu0.005Gd0.990L, Dy0.006Eu0.006Gd0.988L, Dy0.0002Sm0.001Gd0.9988L and Tb0.002Sm0.006Gd0.992L (the value refer to the starting molar ratios of Ln3+ ions).

Recently, layered bismuth oxyhalides (BiOX) have been a well-deserved hotspot in the field of photocatalysis owning to their fascinating physicochemical properties derived from unique layered structures. Nevertheless, insufficient sunlight absorption, rapid recombination of electron-hole (e--h+) pairs, finite carrier concentration, and weak interaction between BiOX surface and reactant molecules inevitably limit the photocatalytic performance of BiOX. Given this, vacancy engineering, which can unleash the great potential to manipulate crystal and electronic structures and surface chemistry of BiOX, is widely applied to improve BiOX to meet the increasingly diverse theoretical and applicable needs. In this review, we focus on recent development in the design of appropriate vacancies on the BiOX for photocatalytic application. The introduction and analysis of popular vacancies creating approaches for BiOX and techniques to distinguish various vacancies are provided. The inherent functionality of BiOX vacancies in photocatalysis at the molecular level is clarified. Then we present representative photocatalytic applications, performance, and corresponding vacancy behavior of vacancy-mediated BiOX. Finally, based on an unambiguous understanding of the vacancy–property relationships and a complete view of the state of the art of vacancy-mediated BiOX, the future directions and possibilities for the rational design of vacancies to acquire ideal properties are explored.

A new three-dimensional manganese-based metal–organic framework Mn4L2(HL)(H2O)5, (1), based on semi-rigid 5-((4′-(tetrazol-5′’-yl)benzyl)oxy)isophthalic acid ligand (H3L) have been prepared and characterized under solvothermal condition. In the structure of 1, trinuclear Mn3O13N2 units are linked each other by sharing vertex and edge to form left- and right- hand helical O-Mn-O chains along b axis, then adjacent left and right handed helical chains are interconnected by L3− and HL2− ligands to generate a 2D layer and L3− ligands with mode II connect the neighboring layers to form a 3D network. 1 shows high stability under different pH conditions and various organic solvents. After activation, 1 exhibits excellent catalytic properties for two typical C C bond reactions, cyanosilylation and Knoevenagel condensation reaction of aldehydes, under solvent-free conditions at room temperature.

Sc-CP 1, 1A, 1B and 1C with controllable morphologies were successfully synthesized by the conventional hydrothermal method and microwave (MW) assisted hydrothermal method. 1 was macroscopic, 1A was nano sized, while 1B and 1C were micron sized. Sc-CP 1 showed two-dimensional (2D) layered structure which was constructed from the connections of left- and right-hand helical chains. Catalytic experiments showed the catalytic performances of Sc-CP 1, 1A, 1B and 1C for the cyanosilylation reaction of aromatic aldehydes were dependent on the morphologies of the particles. Flower-ball-like 1C featuring a high concentration of Lewis acidic Sc(III) sites on its exposed external surfaces showed better catalytic activity than others, the best constant rate of which was 6.4 ​× ​10−3 min−1.

Two new three-dimensional (3D) Sc(III)-based metal organic frameworks (MOFs) [Sc2(OH)2(TDC)2]·4H2O (1) and [Sc3O(fum)3(H2O)3(NO3)]·DMF (2) (H2TDC = 2,5-thiophenedicarboxylic acid, H2fum = fumaric acid) have been hydrothermally synthesized. For 1, TDC2− ligands connect infinite one-dimensional (1D) -Sc-OH-Sc-OH- chains to form open-framework with rhombic channels along the a axis. In 2, flexible fum2− ligands link adjacent trimer [Sc3O(COO)6(H2O)3] secondary building units showing hexagonal-closed circular pores with a diameter of approximate 9.9 A. Furthermore, the desolvated material la can retain the framework, presenting good catalytic activity, significant universality and substrate-selectivity for Strecker-type reactions of trimethylsilyl cyanide (TMSCN) and various aromatic aldimines, especially for N-benzyl 4-methoxybenzaldimine.