Da-Dong Liang

Highly Stable Crystalline Catalysts Based on a Microporous Metal-Organic Framework and Polyoxometalates

A series of remarkable crystalline compounds [Cu(2)(BTC)(4/3)(H(2)O)(2)](6)[H(n)XM(12)O(40)].(C(4)H(12)N)(2) (X = Si, Ge, P, As; M = W, Mo) were obtained from the simple one-step hydrothermal reaction of copper nitrate, benzentricaboxylate (BTC), and different Keggin polyoxometalates (POMs). In these compounds, the catalytically active Keggin polyanions were alternately arrayed as noncoordinating guests in the cuboctahedral cages of a Cu-BTC-based metal-organic framework (MOF) host matrix. X-ray crystallographic analyses, TG, FT-IR, UV-vis, N(2) adsorption studies, and acid-base titration demonstrated their high stability and toleration for thermal and acid-base conditions. No POM leaching or framework decomposition was observed in our study. The representative acid catalytic performance of a compound containing PW(12) species was assessed through the hydrolysis of esters in excess water, which showed high catalytic activity and can be used repeatedly without activity loss. Moreover, catalytic selectivity, which is dependent on the molecular size of substrates, and substrate accessibility for the pore surface were observed. It is the first time that the well-defined, crystalline, MOF-supported POM compound has behaved as a true heterogeneous acid catalyst. The unique attributes of MOF and well-dispersed level of POMs prohibited the conglomeration and deactivation of POMs, which allowed for the enhancement of their catalytic properties.

A Sodalite-Type Porous Metal−Organic Framework with Polyoxometalate Templates: Adsorption and Decomposition of Dimethyl Methylphosphonate

A sodalite-type porous metal-organic framework with polyoxometalate templates, H(3)[(Cu(4)Cl)(3)(BTC)(8)](2)[PW(12)O(40)]·(C(4)H(12)N)(6)·3H(2)O (NENU-11; BTC = 1,3,5-benzenetricarboxylate), was obtained by a hydrothermal reaction. As a reasonable candidate for eliminating nerve gas, NENU-11 displays good adsorption behavior for dimethyl methylphosphonate (15.5 molecules per formula unit). In virtue of the catalytic activity of polyoxometalate guests, this nerve gas mimic could be facilely decomposed by a hydrolysis reaction.

A 9-connected metal–organic framework with gas adsorption properties

A 9-connected, trinuclear cluster-based microporous metal–organic framework, Ni3(OH)(Ina)3(BDC)1.5 (Ina = isonicotinate and BDC = 1,4-benzenedicarboxylate) (1), was synthesized and characterized. The structure is constructed from a 3D channel and two kinds of cages (tetrahedron and triangular pyramid cages). Compound 1 is microporous with a BET surface area of 1255 m2 g−1. It has been observed that the amount of adsorbed benzene (22.60%) is much higher than that of cyclohexane (1.40%), showing its potential to separate benzene and cyclohexane.

Synthesis, structure, and catalytic activity of Keggin-type polyoxometalate coordinated Cu(I): {[Cu(py)2]4[SiW12O40]}, via hydrothermal decarboxylation

A Keggin-type polyoxometalate [SiW12O40]4− supported transition metal complex, {[Cu(py)2]4[SiW12O40]} (py = pyridine), has been synthesized by hydrothermal decarboxylation and characterized by elemental analyses, IR spectra, thermal stability analyses, and single-crystal X-ray diffraction. The compound is a 1-D chain containing an inorganic–organic backbone with alternating [SiW12O40]4− clusters and [Cu(py)2]+ along the c-axis, and with both three- and four-coordinate copper. The luminescence properties indicated that the emission peak is emission of pyridine, assigned to the Cu(I) to pyridine charge transfer. This air-stable Cu(I) complex can efficiently catalyze the O-arylation of both phenols and aryl halides.