Heterometallic metal-organic frameworks: two-step syntheses, structures and catalytic for imine synthesis

Herein, two heterometallic metal organic frameworks were reported by two-step synthesis strategies. By employing the neutral {(Fe2ZnO)-Zn-III(O2CCCl3)(6)(CH3OH)(3)} (1) metalloligand precursor, two new heterometallic {Fe-2(II/III)-Zn} cluster-based coordination polymers, namely, {[(Fe2Zn)-Zn-II/III(BDC)(4)]center dot NH2(Me)(2)}(n) (MOF2) and {[(Fe2Zn)-Zn-II/III(mu(3)-O) (BTC)(2)(CH3CH2CH2OH)]center dot NH2(Me)(2)}(n) (MOF3), were synthesized and structurally character-ized. MOF2 exhibited 8-connected 3D bcg topological net based on (Fe2Zn)-Zn-II/III(OCO)(6) heterometallic unit. MOF3 showed 3D framework based on (Fe2Zn)-Zn-II/III(mu(3)-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.

Automated summary

Two heterometallic metal organic frameworks, MOF2 and MOF3, were synthesized by two-step strategies. These frameworks exhibited different topological structures and contained FeII and FeIII ions in a 1:1 ratio. Additionally, the transformation process involved dissolution, self-reduction of FeIII to FeII, and the cleavage/regeneration of coordination bonds, with heterogeneous catalytic effects observed in the synthesis of imines under solvent-free conditions.