Heterometallic MOFs constructed from thiophene and furandicarboxylate ligands for heavy metal luminescence sensing

Abstract

Rational design of a series of new heterometallic MOFs was carried out by the judicious choice of the corresponding synthesis conditions and ligand geometry. Three heterometallic MOFs (H₂NMe₂)[LiZn(dmf)(tdc)₂]·DMF·H₂O (1), [{LiZn}₂Li₂Zn₂(dmf)₆(tdc)₆]·6DMF·H₂O (2) and [Li₂Zn₂(dmf)₂(fdc)₃]·2DMF·2H₂O (3) were obtained on the basis of the pre-synthesized pivalate complex [Li₂Zn₂(py)₂(piv)₆]. The angle between carboxylic groups greatly affects the possibility of retaining the initial tetranuclear node in the structure of the obtained MOFs. Compound 3 demonstrates permanent porosity with a calculated BET surface area value of 287 m² g⁻¹. Compounds 2 and 3 are capable of heavy metal sorption from their nitrate solution, and a significant flare-up of the luminescence of the obtained inclusion compounds is observed, where the quantum yield of luminescence increases by an order of magnitude in the case of cadmium inclusion.