Lanthanide contraction effect and white-emitting luminescence in a series of metal–organic frameworks based on 2,5-pyrazinedicarboxylic acid

Abstract

A series of lanthanide and yttrium MOFs of two structural types [M₂(H₂O)₂(nmp)₂(pzc)₃] (1M) and [M₂(H₂O)₄(pzc)₃]·NMP·5H₂O (2M) (where M – lanthanide or yttrium cation, nmp – N-methyl-2-pyrrolidone, pzc²⁻ – 2,5-pyrazinedicarboxylate) was synthesized and characterized by single crystal and powder X-ray diffraction crystallography, TG, elemental analyses and IR-spectroscopy. The effect of lanthanide contraction has led to the fact that lanthanides at the beginning of the series (from lanthanum to gadolinium) have a structure different from the structure of lanthanides at the end of the series and yttrium (from terbium and beyond). According to PXRD patterns of the obtained samples mixed metal materials could be obtained not only as crystalline mixtures of two structure types but also as crystalline products of single structure type. Varying the ratio of lanthanides in the initial reaction mixture allowed us to obtain a wide color range of luminescence, including several near-white-light emitting samples.