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Novel Lanthanide(III) Porphyrin-Based Metal–Organic Frameworks: Structure, Gas Adsorption, and Magnetic Properties
journal contribution
posted on 2021-09-17, 23:43 authored by Nikolas Király, Vladimír Zeleňák, Nina Lenártová, Adriana Zeleňáková, Erik Čižmár, Miroslav Almáši, Vera Meynen, Andrej Hovan, Róbert GyepesThe present work
focuses on the hydrothermal synthesis and properties
of porous coordination polymers of metal–porphyrin framework
(MPF) type, namely, {[Pr4(H2TPPS)3]·11H2O}n (UPJS-10), {[Eu/Sm(H2TPPS)]·H3O+·16H2O}n (UPJS-11), and
{[Ce4(H2TPPS)3]·11H2O}n (UPJS-12) (H2TPPS = 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrakisbenzenesulfonate(4-)).
The compounds were characterized using several analytical techniques:
infrared spectroscopy, thermogravimetric measurements, elemental analysis,
gas adsorption measurements, and single-crystal structure analysis
(SXRD). The results of SXRD revealed a three-dimensional open porous
framework containing crossing cavities propagating along all crystallographic
axes. Coordination of H2TPPS4– ligands
with Ln(III) ions leads to the formation of 1D polymeric chains propagating
along the c crystallographic axis. Argon sorption
measurements at −186 °C show that the activated MPFs have
apparent BET surface areas of 260 m2 g–1 (UPJS-10) and 230 m2 g–1 (UPJS-12). Carbon dioxide adsorption isotherms at 0
°C show adsorption capacities up to 1 bar of 9.8 wt % for UPJS-10 and 8.6 wt % for UPJS-12. At a temperature
of 20 °C, the respective CO2 adsorption capacities
decreased to 6.95 and 5.99 wt %, respectively. The magnetic properties
of UPJS-10 are characterized by the presence of a close-lying
nonmagnetic ground singlet and excited doublet states in the electronic
spectrum of Pr(III) ions. A much larger energy difference was suggested
between the two lowest Kramers doublets of Ce(III) ions in UPJS-12. Finally, the analysis of X-band EPR spectra revealed the presence
of radical spins, which were tentatively assigned to be originating
from the porphyrin ligands.
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present work focusesexcited doublet statesargon sorption measurementsadsorption capacities decreasedln ( iiism ( h12 . b3 sub2 sub2 suppr ( iiiporous coordination polymersce ( iiigas adsorption measurementstpps )< subtpps )]· h20 ° c4 – sup10 bcrystal structure analysisc gas adsorptionthermogravimetric measurements{[ pr{[ ce>< sub(< btentatively assignedsxrd revealedsxrd ).respective coradical spinsnovel lanthanideinfrared spectroscopyhydrothermal synthesiselemental analysiselectronic spectrumcrystallographic axiscrystallographic axesactivated mpfs1 bar