Metal–organic frameworks with improved moisture stability based on a phosphonate monoester: effect of auxiliary N-donor ligands on framework dimensionality

Abstract

A series of metal–organic frameworks (MOFs) based on a phosphonate monoester ligand, with structures featuring 1D chains, 2D layers or double layers, and 3D networks, have been successfully obtained in the presence of auxiliary N-donor ligands. The phosphonate monoester, behaving as a carboxylate linker, bridges metal ions, while the auxiliary N-donor ligands play a crucial role in both the structural diversity and the dimensionality variation of the resultant MOFs. Remarkably, the hydrophobic ethyl groups present in the phosphonate monoester linker offer protection/shielding for the hydrolytically vulnerable M–O bonds, resulting in the MOFs being highly moisture stable, as expected. The porous MOFs with 3D networks exhibited CO₂ adsorption and strong fluorescence emission.