Metal-organic frameworks constructed from versatile [WS _4Cu _x] ~(x-2) units: Micropores in highly interpenetrated systems

摘要

Five metal-organic frameworks (MOFs) formed by [WS _4Cu _x] ~(x-2) secondary building units (SBUs) and multi-pyridyl ligands are presented. The [WS _4Cu _x] ~(x-2) SBUs function as network vertexes showing various geometries and connectivities. Compound 1 contains one-dimensional channels formed in fourfold interpenetrating diamondoid networks with a hexanuclear [WS _4Cu _5] ~(3+) unit as SBU, which shows square-pyramidal geometry and acts as a tetrahedral node. Compound 2 contains brick-wall-like layer also with a hexanuclear [WS _4Cu _5] ~(3+) unit as SBU. The [WS _4Cu _5] ~(3+) unit in 2 is a new type of [WS _4Cu _x] ~(x-2) cluster unit in which the five Cu ~+ ions are in one plane with the W atom, forming a planar unit. Compound 3 shows a nanotubular structure with a pentanuclear [WS _4Cu _4] ~(2+) unit as SBU, which is saddle-shaped and acts as a tetrahedral node. Compound 4 contains large cages formed between two interpenetrated (10,3)-a networks also with a pentanuclear [WS _4Cu _4] ~(2+) unit acting as a triangular node. The [WS _4Cu _4] ~(2+) unit in 4 is isomeric to that in 3 and first observed in a MOF. Compound 5 contains zigzag chains with a tetrahedral [WS _4Cu _3] ~+ unit as SBU, which acts as a V-shaped connector. The influence of synthesis conditions including temperature, ligand, anions of Cu I salts, and the ratio of [NH _4] _2WS _4 to Cu ~I salt on the formation of these [WS _4Cu _x] ~(x-2)-based MOFs were also studied. Porous MOF _3 is stable upon removal and exchange of the solvent guests, and when accommodating different solvent molecules, it exhibits specific colors depending on the polarity of incorporated solvent, that is, it shows a rare solvatochromic effect and has interesting prospects in sensing applications. Versatile SBUs: [WS _4Cu _x] ~(x-2) units show different geometries and connectivities when used as secondary building units (SBUs) for constructing metal-organic frameworks (MOFs; see figure). Temperature and ligand are more important parameters for the synthesis of new [WS _4Cu _x] ~(x-2)-based MOFs than the ratio of [NH _4] _2WS _4 to Cu ~I salt.