Synthesis of multifunctional metal–organic frameworks and tuning the functionalities with pendant ligands

Abstract

A series of multifunctional metal–organic frameworks (MOFs), SNU-170–SNU-176, has been synthesized using ligands, in which various functional pendants such as –NH₂, –SMe, –OMe, –OEt, –OPr, and –OBu are attached to the phenyl ring of 4-(2-carboxyvinyl)benzoic acid. The MOFs are isostructural but the interpenetration depends on the pendant group of the ligand. The MOFs exhibit high adsorption capacities for H₂, CO₂, and CH₄ gases, ligand-based photoluminescence, and chemical sensing abilities, all being affected by the pendant group. All of the as-synthesized MOFs can sense nitroaromatics by luminescence quenching, and some of the activated MOFs can sense the type of solvents by the altered emission maxima with enhanced intensity. In particular, SNU-176 synthesized from a mixture of two different ligands with –SMe and –OMe pendants shows higher gas adsorption capacities than the MOFs synthesized from the individual ligands (SNU-171 and SNU-172). It also shows the ability to differentiate nitrobenzene (NB) and 2,4-dinitrotoluene (DNT) unlike the MOFs composed of single ligands.