Hydrothermal synthesis, ab-initio structure determination and NMR study of the first mixed Cu–Al fluorinated MOF

Abstract

Herein, the first fluorinated heterometallic metal–organic framework (MOF) containing both Cu(II) and Al(III) cations is presented. CuAlF_4.5(OH)_0.5(H₂O)[HAmTAZ]₂ (HAmTAZ = 3-amino-1,2,4-triazole) was hydrothermally synthesized. The structure of this paramagnetic compound was solved using the SDPD method (structural determination by powder diffractometry) and confirmed by ¹H, ¹⁹F and ²⁷Al solid-state nuclear magnetic resonance (NMR) experiments. The structure (space group Ima2, a = 16.306(3) Å, b = 8.9356(3) Å, c = 8.2884(2) Å) can be described from the Cu–HAmTAZ layers connected by AlF₅H₂O octahedra, generating a three-dimensional network with a pcu topology. This compound illustrates that from 2D MOFs within the M(HTAZ)₂(NCS)₂ (M = Mn, Fe, Co, Ni, Cu, Zn) system, insertion of AlF₅H₂O octahedra building units between the Cu–HAmTAZ layers provides a way to generate 3D F-MOFs.