Four alkaline earth metal (Mg, Ca, Sr, Ba)-based MOFs as multiresponsive fluorescent sensors for Fe3+, Pb2+ and Cu2+ ions in aqueous solution

摘要

A series of new alkaline earth-metal organic frameworks (AE-MOFs), i.e. {[Mg-2(mu(6)-L)(mu(2)-OH2)(H2O)(4)]-DMF}(n) (1), [Ca-2(mu(10)-Q(EtOH)](n) (2), [Sr(mu(6)-H2L)(MeOH)](n) (3) and {[Ba-1.5(mu(5)-H2L)(mu(4)-H3L)(H2O)(3)}center dot 2(H2O)}(n)(4) were synthesized under solvothermal reaction by employing a symmetrical V-shaped multicarboxylic acid ligand H4L (H4L = 5,5'-oxydiisophthalic acid), resulting in versatile coordination modes as well as various topologies. 1 forms a uninodal 4-connected (6(6))-dia 3D topology based on dinuclear Mg-2(COO)(2)(mu(2)-OH2) clusters. 2 displays an unprecedented 3-nodal (5,5,10)-connected 3D net with (4(24).6(21))(4(8).6(2))(2) topology based on 1D [Ca(COO)](n) chains and dinuclear Ca-2(COO)(2) clusters. 3 indicates a uninodal 6-connected 3D net with (4(10).6(5))-sma topology based on 1D [Sr(COO)] chains. 4 features a new 4-nodal (4,5,6,6)-connected net with (4(3).6(3))2(4(6).6(4))(2)(4(6.)6(8).8)(4(6).6(9))(2) topology based on two types of 1D chains. 1-4 show solid-state fluorescent. properties at ambient temperature. Especially, 1 and 2 have multiresponsive recognition of Fe3+ and Pb2+ ions, Fe3+ and Cu2+ ions, respectively, while 3 and 4 show single selective detection for Fe3+ ion, signifying that they could be potential fluorescent sensors for specific heavy metal ions in water system. The sensing mechanism has also been discussed in detail.