Metal-Organic Frameworks Constructed from 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

Five new metal-organic frameworks based on 2,4,6-tris(4-pyridyl)-1,3,5-triazine (tpt) ligand have been hydrothermally synthesized. Reaction of tpt and AgNO₃ in an acidic solution at 180 °C yields {[Ag(Htpt)(NO₃)]NO₃·4H₂O}_n (1). Ag(I) is trigonally coordinated by two pyridyl nitrogen and one nitrato oxygen to form a 1D zigzag chain. Reaction of tpt with CuSO₄ affords {[Cu₂(tpt)₂(SO₄)₂(H₂O)₂]·4H₂O}_n (2). Copper(II) is bonded to two pyridyl nitrogen, two sulfato oxygen, and two water oxygen atoms to form an elongated octahedral geometry. Each H₂O ligand bridges two copper(II), whereas sulfate bridges copper(II) via µ-1,3 and µ-1,1 fashions. The copper(II)−sulfate−H₂O 2D layers are linked by bidentate tpt to form a 3D polymeric structure. Reaction of Cu(SO₄)₂, tpt, and 1,2,4,5-benzenetetracarboxylic acid (H₄btec) in the presence of piperidine gives [Cu(tpt)(H₂btec)_1/2]_n (3). Copper(I) is located in a trigonal-pyramidal coordination environment and coordinated by three pyridyl nitrogen of tpt in a plane, whereas a carboxylate oxygen is coordinated to the copper(I) axially. The tpt−Cu forms a layer, and the layers are linked through H₂btec²⁻ to form a 2D double-layered coordination polymer. Replacing CuSO₄ with ZnI₂ in the synthesis gives {[Zn(tpt)(btec)_1/2]·H₂O}_n (4). Zinc(II) is in a distorted tetrahedral geometry and linked through bidentate tpt and exotetradentate btec⁴⁻ to form a 2D coordination grid. Reaction of tpt with CuCN leads to the assembly of a 3D metal-organic framework [Cu₃(CN)₃(tpt)]_n (5). Copper(I) is trigonally coordinated by one pyridyl nitrogen and two cyanides to form an intriguing honeycomb architecture. Luminescence study shows that 1, 3, 4, and 5 have blue fluorescence, which can be assigned to be ligand-centered emissions. Thermal analysis shows that all of these complexes are quite stable, and especially for 4, the framework is stable up to 430 °C.