Syntheses and Structural Characterization of Lithium Carboxylate Frameworks and Guest-Dependent Photoluminescence Study

Five novel 3D lithium–organic frameworks, [Li2(H2pml)]·C4H8O2 (1, H4pml = 1,2,4,5-benzenetetracarboxylic or pyromellitic acid), [Li2(H2pml)] (2), [Li­(H2tatab)]·5H2O (3, H3tatab = 4,4′,4″-s-triazine-1,3,5-triyltri-p-aminobenzoic acid), [Li11(H3O)­(H2O)5(Html)6]·8C4H8O2 (4, H3tml = 1,2,4-benzenetricarboxylic or trimellitic acid), and [Li­{Li­(nmp)}­{Li­(H2O)­(nmp)}­{Li­(nmp)2}2(H2tms)­(Htms)2]·NMP·EtOH (5, H3tms = 1,3,5-benzenetricarboxylic or trimesic acid, nmp = 1-methyl-2-pyrrolidinone), were synthesized by solvothermal methods and characterized by single crystal X-ray diffraction, powder X-ray diffraction (PXRD), IR spectroscopy, and thermogravimetric analyses (TGA). Compounds 1 and 2 feature the same framework composition but different guest-controlled structures and topology. Compound 4 consists of a unique undecanuclear Li carboxylate complex {Li11(H2O)5(RCOO)18} and contains pores with diameter 7 Å. Furthermore, compound 4 demonstrates highly pronounced guest-dependent photoluminescence behavior: nitrobenzene completely quenches the light emission, while toluene enhances it.