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

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.