The influence of coordination modes and active sites of a 5-(triazol-1-yl) nicotinic ligand on the assembly of diverse MOFs

Abstract

Six new complexes based on 5-(triazol-1-yl)nicotinic acid (HL), namely [Cu₂(L)₃(H₂O)(OH)]_n (1), [Co(L)₂(H₂O)₂]_n (2), [Mn(L)₂(H₂O)₂]_n (3), {[Co(L)(H₂O)_0.5(DMF)_0.5(NO₃)_0.5]·(Cl)_0.5·DMF·2H₂O}_n (4), {[Cu(L)(O)_0.5]·CH₃OH·2.5H₂O}_n (5) and {[Co₂(L)₄(H₂O)]·2DMA·2H₂O}_n (6), were synthesized under hydro(solvo)thermal conditions. The L⁻ ligand in 1–6 reveals various coordination modes and forms diverse secondary building units (SBUs) in the final structures. Complex 1 shows a 2D layered structure with a rare (3,8)-connected topology based on tetranuclear [Cu₄(COO)₆(H₂O)₂(OH)₂N₆] SBUs. 2 and 3 are isostructural and display 2D 4-connected sql nets with a point symbol of (4⁴·6²). 4 and 5 have similar spatial 3D porous frameworks, which can be simplified as a (3,6)-connected 2-nodal net via dinuclear [Co₂(COO)₂(O)₂(NO₃)(N)₄] SBUs and [Cu₂(COO)₂(O)(N)₄] SBUs, respectively. 6 is a 3D porous framework constructed by dinuclear [Co₂(COO)₄(H₂O)(N)₄] motifs with a uninodal 4-connected qtz net. The magnetic properties and gas sorption behaviour of these complexes were investigated carefully, showing that 3 exhibits ferrimagnetic character and 4 demonstrates its effective storage capacity for CO₂ as well as high selectivity for CO₂ over CH₄ under ambient conditions.