3 research outputs found
Enhancement of CO2 uptake and selectivity in a metal-organic framework by incorporation of thiophene functionality
The complex [Zn2(tdc)2dabco] (H2tdc = thiophene-2,5-dicarboxylic acid; dabco = 1,4-diazabicyclooctane) shows a remarkable increase in CO2 uptake and CO2/N2 selectivity compared to the non-thiophene analogue [Zn2(bdc)2dabco] (H2bdc = benzene-1,4-dicarboxylic acid; terephthalic acid). CO2 adsorption at 1 bar for [Zn2(tdc)2dabco] is 67.4 cm3 x g–1 (13.2 wt.%) at 298 K and 153 cm3 x g–1 (30.0 wt.%) at 273 K. For [Zn2(bdc)2dabco] the equivalent values are 46 cm3 x g–1 (9.0 wt.%) and 122 cm3 x g–1 (23.9 wt.%), respectively. The isosteric heat of adsorption for CO2 in [Zn2(tdc)2dabco] at zero coverage is low (23.65 kJ x mol–1), ensuring facile regeneration of the porous material. The enhancement by the thiophene group on the separation of CO2/N2 gas mixtures has been confirmed by both ideal adsorbate solution theory (IAST) calculations and dynamic breakthrough experiments. The preferred binding sites of adsorbed CO2 in [Zn2(tdc)2dabco] have been unambiguously determined by in situ single crystal diffraction studies on CO2 loaded [Zn2(tdc)2dabco], coupled with quantum chemical calculations. These studies unveil the role of the thiophene moieties in the specific CO2 binding via an induced dipole interaction between the CO2 and the sulfur center, confirming that enhanced CO2 capacity in [Zn2(tdc)2dabco] is achieved without the presence of open metal sites. The experimental data and the theoretical insights suggest a viable strategy for improvement of adsorption properties of already known materials through incorporation of S-based heterocycles within their porous structures
Enhancement of CO<sub>2</sub> Uptake and Selectivity in a Metal–Organic Framework by the Incorporation of Thiophene Functionality
The complex [Zn<sub>2</sub>(tdc)<sub>2</sub>dabco] (H<sub>2</sub>tdc = thiophene-2,5-dicarboxylic
acid; dabco = 1,4-diazabicyclooctane) shows a remarkable increase
in carbon dioxide (CO<sub>2</sub>) uptake and CO<sub>2</sub>/dinitrogen
(N<sub>2</sub>) selectivity compared to the nonthiophene analogue
[Zn<sub>2</sub>(bdc)<sub>2</sub>dabco] (H<sub>2</sub>bdc = benzene-1,4-dicarboxylic
acid; terephthalic acid). CO<sub>2</sub> adsorption at 1 bar for [Zn<sub>2</sub>(tdc)<sub>2</sub>dabco] is 67.4 cm<sup>3</sup>·g<sup>–1</sup> (13.2 wt %) at 298 K and 153 cm<sup>3</sup>·g<sup>–1</sup> (30.0 wt %) at 273 K. For [Zn<sub>2</sub>(bdc)<sub>2</sub>dabco], the equivalent values are 46 cm<sup>3</sup>·g<sup>–1</sup> (9.0 wt %) and 122 cm<sup>3</sup>·g<sup>–1</sup> (23.9 wt %), respectively. The isosteric heat of adsorption for
CO<sub>2</sub> in [Zn<sub>2</sub>(tdc)<sub>2</sub>dabco] at zero coverage
is low (23.65 kJ·mol<sup>–1</sup>), ensuring facile regeneration
of the porous material. Enhancement by the thiophene group on the
separation of CO<sub>2</sub>/N<sub>2</sub> gas mixtures has been confirmed
by both ideal adsorbate solution theory calculations and dynamic breakthrough
experiments. The preferred binding sites of adsorbed CO<sub>2</sub> in [Zn<sub>2</sub>(tdc)<sub>2</sub>dabco] have been unambiguously
determined by in situ single-crystal diffraction studies on CO<sub>2</sub>-loaded [Zn<sub>2</sub>(tdc)<sub>2</sub>dabco], coupled with
quantum-chemical calculations. These studies unveil the role of the
thiophene moieties in the specific CO<sub>2</sub> binding via an induced
dipole interaction between CO<sub>2</sub> and the sulfur center, confirming
that an enhanced CO<sub>2</sub> capacity in [Zn<sub>2</sub>(tdc)<sub>2</sub>dabco] is achieved without the presence of open metal sites.
The experimental data and theoretical insight suggest a viable strategy
for improvement of the adsorption properties of already known materials
through the incorporation of sulfur-based heterocycles within their
porous structures