Enhancing Gas Adsorption and Separation Capacity through Ligand Functionalization of Microporous Metal–Organic Framework Structures

Abstract

Hydroxyl- and amino- functionalized [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O leads to two new structures, [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O (BDC=terephthalic acid, TED=triethylenediamine, BDC-OH=2-hydroxylterephthalic acid, BDC-NH(2)=2-aminoterephthalic acid). Single-crystal X-ray diffraction and powder X-ray diffraction studies confirmed that the structures of both functionalized compounds are very similar to that of their parent structure. Compound [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O can be considered a 3D porous structure with three interlacing 1D channels, whereas both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O contain only 1D open channels as a result of functionalization of the BDC ligand by the OH and NH(2) groups. A notable decrease in surface area and pore size is thus observed in both compounds. Consequently, [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O takes up the highest amount of H(2) at low temperatures. Interestingly, however, both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O show significant enhancement in CO(2) uptake at room temperature, suggesting that the strong interactions between CO(2) and the functionalized ligands, indicating that surface chemistry, rather than porosity, plays a more important role in CO(2) adsorption. A comparison of single-component CO(2), CH(4), CO, N(2), and O(2) adsorption isotherms demonstrates that the adsorption selectivity of CO(2) over other small gases is considerably enhanced through functionalization of the frameworks. Infrared absorption spectroscopic measurements and theoretical calculations are also carried out to assess the effect of functional groups on CO(2) and H(2) adsorption potentials.

Incorporating the Thiazolo[5,4-d]thiazole Unit into a Coordination Polymer with Interdigitated Structure

“…A higher heat of adsorption is usually indicative for stronger framework CO2 interactions [47]. Representative values are 20kJ/mol for [Zn(1,4-BDC)(TED)], 30 kJ/mol for HKUST-1, 47 kJ/mol for Mg-MOF-74, 63 kJ/mol for MIL-100-Cr and 96 kJ/mol for mmen-Cu-BTTri [48][49][50][51][52]. The heat of adsorption curve ( Figure 8) has a relative maximum at a quantity adsorbed of about 4 cm 3 /g STP with 27.7 kJ/mol.…”

Effect of the structural constituents of metal organic frameworks on carbon dioxide capture

“…In general, functionalization of organic linkers is performed to increase the affinity of the resultant material towards CO 2 molecules and to improve CO 2 selectivity over other molecules [147]. This can be achieved through the tuning of a MOF's physical and chemical properties to design an ideal CO 2 adsorbent, which can make use of both physisorption and chemisorption for capture.…”

The synthesis of mesostructured NH2-MIL-101(Cr) and kinetic and thermodynamic study in tetracycline aqueous solutions

“…Some reports have appeared on the introduction of synthesis a series of functionalized MOFs containing the BDC-X ligand (X = -NH 2 , -OH, -CH 3 and -NO 2 ) [28][29][30][31][32]. For instance, Kim et al [33] have studied that NH 2 -MIL-125 showed a higher catalytic activity and significantly superior CO 2 adsorption capacity than MIL-125.…”