Highly stable and porous porphyrin-based zirconium and hafnium phosphonates - electron crystallography as an important tool for structure elucidation
The Ni-metallated porphyrin-based tetraphosphonic acid (Ni-tetra(4-phosphonophenyl)porphyrin, Ni-H TPPP) was used for the synthesis of highly porous metal phosphonates containing the tetravalent cations Zr and Hf . The compounds were thoroughly characterized regarding their sorption properties towar...
Saved in:
Published in | Chemical science (Cambridge) Vol. 9; no. 24; pp. 5467 - 5478 |
---|---|
Main Authors | , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
England
Royal Society of Chemistry
28.06.2018
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | The Ni-metallated porphyrin-based tetraphosphonic acid (Ni-tetra(4-phosphonophenyl)porphyrin, Ni-H
TPPP) was used for the synthesis of highly porous metal phosphonates containing the tetravalent cations Zr
and Hf
. The compounds were thoroughly characterized regarding their sorption properties towards N
and H
O as well as thermal and chemical stability. During the synthesis optimization the reaction time could be substantially decreased under stirring from 24 to 3 h in glass vials. M-CAU-30, [M
(Ni-H
TPPP)(OH/F)
]·H
O (M = Zr, Hf) shows exceptionally high specific surface areas for metal phosphonates of
= 1070 and 1030 m
g
for Zr- and Hf-CAU-30, respectively, which are very close/correspond to the theoretical values of 1180 and 1030 m
g
. CAU-30 is always obtained as mixtures with one mol ZrO
/HfO
per formula unit as proven by TEM, electron diffraction, TG and elemental analysis. Hence experimentally derived specific surface areas are 970 and 910 m
g
, respectively. M-CAU-30 is chemically stable in the pH range 0 to 12 in HCl/NaOH and thermally up to 420 °C in air as determined by variable-temperature powder X-ray diffraction (VT-PXRD). The crystal structure of M-CAU-30 was determined by combining electron diffraction tomography for structure solution and powder X-ray diffraction data for the structure refinement. The crystal structure consists of chains of corner sharing MO
octahedra interconnected by the partly deprotonated linker molecules Ni-H
TPPP
. Thus 1D channels with pore diameters of 1.3 × 2.0 nm are formed. The redox activity of Zr-CAU-30 was investigated by cyclic voltammetry resulting in a reversible redox process at a half-wave potential of
= -0.649 V. |
---|---|
Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 2041-6520 2041-6539 |
DOI: | 10.1039/c8sc01533c |