Heterometallic metal-organic frameworks: Two-step syntheses, structures and catalytic for imine Synthesis

Abstract Herein, two heterometallic metal organic frameworks were reported by two-step synthesis strategies. By employing the neutral {Fe2IIIZnO(O2CCCl3)6(CH3OH)3} (1) metalloligand precursor, two new heterometallic{Fe2II/III-Zn} cluster-based coordination polymers, namely, {[FeII/III2Zn(BDC)4]•NH2(Me)2}n (MOF2) and {[FeII/III2Zn(μ3-O) (BTC)2(CH3CH2CH2OH)]·NH2(Me)2}n (MOF3), were synthesized and structurally characterized. MOF2 exhibited 8-connected 3D bcg topological net based on FeII/III2Zn(OCO)6 heterometallic unit. MOF3 showed 3D framework based on FeII/III2Zn(μ3-O) (OCO)4 trinuclear unit with binodal (3,6)-connected scu/p topology, and possessed two kinds of 1D hydrophobic and hydrophilic open channel along the c axis. Interestingly, both FeII and FeIII ions with 1:1 ratio were observed in the trinuclear unit and confirmed by bond valence sum (BVS), X-ray photoelectron spectroscopy (XPS) and Mossbauer spectroscopy studies. The transformation was accompanied by the dissolution, self-reduction of FeIII to FeII and the cleavage/regeneraion of coordination bonds. Meanwhile, the heterogeneous catalytic effects for one-pot synthesis of imine from amine and alcohols under solvent-free conditions were also studied.