Organic-inorganic hybrid 1-D double chain heteropolymolybdates constructed from plenary Keggin germanomolybdate anions and hepta-nuclear Cu-RE-pic heterometallic clusters.

Two unprecedented organic-inorganic hybrid 1-D double chain germanomolybdates containing hepta-nuclear Cu-RE-pic heterometallic clusters [NH4]2[RE(H2O)5]2[Cu(pic)2]2[Cu(pic)2(H2O)2]3[α-GeMo12O40]2·22H2O [RE = La3+ (1), Ce3+ (2), and Hpic = 2-picolinic acid] were successfully obtained by the stepwise self-assembly strategy via the conventional solution method. The most striking structural feature of 1 and 2 is that the two plenary Keggin [α-GeMo12O40]4- polyoxoanions are joined by an organic-inorganic hybrid hepta-nuclear Cu-RE-pic {[RE(H2O)5]2[Cu(pic)2(H2O)2]3[Cu(pic)2]2}6+ heterometallic moiety. What is more interesting is that their adjacent structural units are connected together by {Cu(pic)2} bridges, forming a 1-D extended double chain architecture. Furthermore, the adsorption capacity of 1 toward dyes in aqueous solutions was deeply investigated. It is fascinating that 1 shows a good adsorption capacity toward basic violet 3 (BV 3) in aqueous solutions and the adsorption kinetics conforms to the second-order kinetic model.