cg501273b_si_001.pdf (472.49 kB)
Phase Formation Study of Ca-Terephthalate MOF-Type Materials
journal contribution
posted on 2015-02-04, 00:00 authored by Matjaž Mazaj, Nataša Zabukovec LogarCa(BDC)(DMF)(H2O) with square lattice topology (sql)
and rhombic-shaped channels crystallizes under solvothermal conditions
(H2O/DMF mixture) in orthorhombic (Ca-BDC-orth) and triclinic (Ca-BDC-tric) conformations. The
latter structure is solved and described here for the first time.
The main difference between the two phases lies in the orientation
of the coordinated DMF molecule located within the channels of the
structure, influencing their porosity properties. In spite of the
small deviances in crystal structure, the formation of individual
phases can be controlled by the amount of base agent (TEA) and the
temperature of crystallization. Triclinic phase is formed at lower
synthesis temperature, and it is transformed into orthorhombic phase
at increased temperatures. Systematic phase formation study varying
TEA/Ca2+ molar ratios and the synthesis temperature showed
that higher temperature of the synthesis is required for the Ca-BDC-orth phase to occur from Ca-BDC-tric using
the TEA/Ca2+ ratio between 0.63–1.30 compared to
the syntheses with TEA/Ca2+ values out of this range. Within
the range of 0.63–1.30 the dissociation of the base is in the
buffer region indicating that stability of triclinic phase is related
to the thermodynamics at equilibrium conditions.