Metal-organic Framework Compound Research Articles

Improved synthesis, thermal stability and catalytic properties of the metal-organic framework compound Cu 3(BTC) 2

The catalytic properties of the metal-organic framework compound Cu 3(BTC) 2(H 2O) 3 · xH 2O (BTC=benzene 1,3,5-tricarboxylate) were explored. Cu 2O-free powder samples of Cu 3(BTC) 2(H 2O) 3 · xH 2O were obtained using an improved synthesis at 393 K under hydrothermal conditions. The microporous material has a high specific pore volume of 0.41 cm 3 g −1 and a pore diameter of 10.7 Å (Horvath-Kawazoe). Removal of the three copper-bound water molecules allows to access the Lewis acid copper sites. The exchange of coordinated water by substrates or solvent molecules is recognized from the color change of the compound. For chemisorbed benzaldehyde, the IR stretching frequency ν(CO) is decreased from 1702 to 1687 cm −1. The chemisorption results in an activation of benzaldehyde for the liquid phase cyanosilylation with a reasonable yield of 50–60% after 72 h (313 K) and a high selectivity. Filtration experiments demonstrate that the reaction mechanism is heterogeneous. Coordinating solvents such as THF completely block the Lewis acid sites of the catalyst. Solvents such as CH 2Cl 2 or higher reaction temperatures (353 K) cause decomposition of the catalyst.

Poly[[aquaneodymium(III)]-micro(3)-decane-1,10-dicarboxylato-micro(3)-9-carboxynonanecarboxylato

The title compound, [Nd(C(10)H(16)O(4))(C(10)H(17)O(4))(H(2)O)](n), has a novel Nd-organic framework constructed from sebacic acid (C(10)H(18)O(4)) linkers, the longest aliphatic ligand used to date in lanthanide metal-organic framework compounds. The structure contains edge-shared chains of NdO(8)(H(2)O) tricapped trigonal prisms that propagate in the [100] direction, with Nd-O distances in the range 2.414 (4)-2.643 (4) A.

Advances in the chemistry of metal–organic frameworks

An extensive body of research results currently exists from the synthesis of metal–organic frameworks (MOFs), an area that has attracted widespread attention due to the facility with which well-defined molecular building blocks can be assembled into periodic frameworks and the promise that such a process holds for the logical design of materials. The synthesis of MOFs generally involves the copolymerization of organic links and metal ions in a polar solvent under mild temperatures (up to 200 °C) and autogenous pressures (up to 100 atm). Since most products can be considered kinetically driven and lie on local thermodynamic minima, factors such as solubility of the organic link and metal salt, solvent polarity, ionic strength of the medium, temperature and pressure play critical roles in determining the character of products. Indeed, slight perturbations in synthetic parameters have been the basis for the preparation of what seems to be a flood of new MOF compounds. In the spirit of this discussion we advance the following ideas and developments that we believe contribute to the maturity of the field: (I) a conceptual framework that unifies the processes involved in the designed synthesis of MOFs, and which can be extended to other materials with extended structures; (II) a thesis concerning the possible structures that may form from building blocks with various shapes; (III) important considerations for achieving the design and synthesis of frameworks in which it is possible to change chemical functionality and metrics without changing the underlying framework topology; (IV) the inevitability of porosity for designed structures and some factors affecting framework stability; (V) insights on catenation: interpenetration versus interweaving, forbidden catenation, and duals. These points will be presented to an extent that will stimulate discussion—it is not an attempt to be comprehensive or to give a thorough treatment of this rich field.