Irreversible High-Temperature Hydrogen Interaction with the Metal Organic Framework Cu3(BTC)2

Unsaturated metal coordination sites in metal organic frameworks (MOFs) offer preferential hydrogen adsorption sites. In addition, MOFs can be applied as scaffolds for nano metal hydrides operating at elevated temvratures. For these reasons, the thermal stability of the framework with unsaturated Cu2+. coordination sites in a hydrogen atmosphere has been investigated in Cu-3(BTC)(2). It is found that Cu-3(BTC)(2) irreversibly binds 1.1 wt % of hydrogen at the temperatures between 323 and 423 K and 2 bar H-2 pressure, which corresponds to three hydrogen atoms per BTC ligand. In accordance, FTIR and NMR spectroscopy show that the BTC linkers are converted to their acid form, whereas XRD reveals the presence of reduced Cu-0 metal particles and decomposition of the framework. When designing more strongly interacting MOFs for H-2 storage applications or as template for light metal hydrides, one has to take possible reduction of the metal centers and the stability of the lattice into account.