A Rationale for the Large Breathing of the Porous Aluminum Terephthalate (MIL‐53) Upon Hydration

Abstract

Aluminum 1,4-benzenedicarboxylate Al(OH)[O(2)C-C(6)H(4)-CO(2)]. [HO(2)C-C(6)H(4)-CO(2)H](0.70) or MIL-53 as (Al) has been hydrothermally synthesized by heating a mixture of aluminum nitrate, 1,4-benzenedicarboxylic acid, and water, for three days at 220 degrees C. Its 3 D framework is built up of infinite trans chains of corner-sharing AlO(4)(OH)(2) octahedra. The chains are interconnected by the 1,4-benzenedicarboxylate groups, creating 1 D rhombic-shaped tunnels. Disordered 1,4-benzenedicarboxylic acid molecules are trapped inside these tunnels. Their evacuation upon heating, between 275 and 420 degrees C, leads to a nanoporous open-framework (MIL-53 ht (Al) or Al(OH)[O(2)C-C(6)H(4)-CO(2)]) with empty pores of diameter 8.5 A. This solid exhibits a Langmuir surface area of 1590(1) m(2)g(-1) together with a remarkable thermal stability, since it starts to decompose only at 500 degrees C. At room temperature, the solid reversibly absorbs water in its tunnels, causing a very large breathing effect and shrinkage of the pores. Analysis of the hydration process by solid-state NMR ((1)H, (13)C, (27)Al) has clearly indicated that the trapped water molecules interact with the carboxylate groups through hydrogen bonds, but do not affect the hydroxyl species bridging the aluminum atoms. The hydrogen bonds between water and the oxygen atoms of the framework are responsible for the contraction of the rhombic channels. The structures of the three forms have been determined by means of powder X-ray diffraction analysis. Crystal data for MIL-53 as (Al) are as follows: orthorhombic system, Pnma (no. 62), a = 17.129(2), b = 6.628(1), c = 12.182(1) A; for MIL-53 ht (Al), orthorhombic system, Imma (no. 74), a = 6.608(1), b = 16.675(3), c = 12.813(2) A; for MIL-53 lt (Al), monoclinic system, Cc (no. 9), a = 19.513(2), b = 7.612(1), c = 6.576(1) A, beta = 104.24(1) degrees.

A Novel Bismuth‐Based Metal–Organic Framework for High Volumetric Methane and Carbon Dioxide Adsorption

“…The total micropore volume calculated from maximum N 2 uptake at saturation is 0.39 cm 3 g -1 , consistent with the total crystallographically-determined pore volume of 0.37 cm 3 g -1 . The pore volume and BET surface area of NOTT-220a are comparable to some of the light metal based MOFs [e.g., MIL-53(Al), 24 NOTT-300(Al) 25 ], and are much higher than the values previously reported for heavy metal based MOFs (e.g., Bi-MOFs 10a-c , UMOFs 26 , Ba-MOFs 27 ), but are lower than those of the most porous MOFs based upon Zn(II) or Cu(II) ions. 4 Gravimetric H 2 adsorption isotherms at 77 K show good reversibility and an absence of hysteresis, and give a total storage capacity of 1.5 wt% at 1.0 bar and 2.8 wt% at 20 bar at 77 K (Figure 3b).…”

New Group 13 MIL‐53 Derivates based on 2,5‐Thiophenedicarboxylic Acid

“…8.5 ϫ 8.5 Å). [19] Arranging each TDC 2-linker is possible in two ways, because it can be rotated around 180°along the connection axis. There is no obvious chemical reason why one of the possibilities should be preferred.…”

Visualizing MOF Mixed Matrix Membranes at the Nanoscale: Towards Structure‐Performance Relationships in CO2/CH4 Separation Over NH2‐MIL‐53(Al)@PI

“…[ 11 ] Metal organic frameworks (MOFs) are recently attracting a lot of attention as potential fi ller materials for MMMs since the pioneering work by Yehia et al [ 12 ] These crystalline nanostructures can be synthesised at mild conditions and display high surface areas and large pore volumes, generally in the micropore range. [ 13 ] Besides, they offer an almost unlimited number Visualizing MOF Mixed Matrix Membranes at the Nanoscale: Towards Structure-Performance Relationships in CO 2 /CH 4 Separation Over NH 2 -MIL-53(Al)@PI Mixed matrix membranes (MMMs) composed of metal organic framework (MOF) fi llers embedded in a polymeric matrix represent a promising alternative for CO 2 removal from natural gas and biogas. Here, MMMs based on NH 2 -MIL-53(Al) MOF and polyimide are successfully synthesized with MOF loadings up to 25 wt% and different thicknesses.…”