Fine tuning of the physico-chemical properties of a MIL-53(Al) type - Mesoporous alumina composite using a facile sacrificial-template synthesis approach

Abstract

Though Metal Organic Frameworks (MOF's) and MOF-derived solids have been employed in various applications, especially catalysis, there is still a constant search for better performing MOF-based hybrid catalysts. In this work, we employed sacrificial template method in synthesizing MIL-53(Al) type-porous Alumina (MA) composites that exhibit different physico-chemical and catalytic properties compared to parent solids (MIL-53 and mesoporous Al 2 O 3). Structural investigations demonstrated that composites possess combined structure of both the parent solids. Novel composites possess hierarchical (meso-& micro-) pores, with average pore width in the range of ~14 to 16 nm. NH 3 adsorption calorimetry and isopropanol test enabled deducting the possible nature and strength of acid-basic sites in composites. 'MA' composites show intermediate chemical properties and synergistic multifunctional catalytic behavior compared to parent solids. This work reveals, for the first time, extensively tunable physico-chemical properties of a novel class of solids: "the MIL-53(Al) type-porous alumina composites" that can have a huge potential as multifunctional catalysts.

Facile synthesis of hierarchically structured MIL-53(Al) with superior properties using an environmentally-friendly ultrasonic method for separating lead ions from aqueous solutions

“…The high crystallinity and porosity of the sample yield a high BET surface area of 1538.6 m 2 /g and a vast average pore size of 1.74 nm. BET surface area and average pore size are greater than those conventionally synthesized MIL-53(Al) introduced in the literature 21 – 23 ; it could be explained by the effect of ultrasound waves on the crystalline structure of MIL-53(Al). Ultrasonic intensity as a driving force ends up in a substantial quantity of cavitation bubbles, and increases in crystallinity, leading to a higher BET expanse in line with the XRD pattern 19 , 24 .…”

“…4 . The synthesized sample resembles an IUPAC-type IV isotherm with a type H4 hysteresis loop, illustrating hierarchical structure including mesoporous and microporous in the sample while conventional synthesis MIL-53(Al) only possesses a microporous structure 21 . Furthermore, BET data of MIL-53(Al) are given in Table 1 .…”

“…Ultrasonic intensity as a driving force ends up in a substantial quantity of cavitation bubbles, and increases in crystallinity, leading to a higher BET expanse in line with the XRD pattern 19 , 24 . Moreover, the high intensity of ultrasonic waves creates mesopores in the structure of MOFs 25 , leading to a hierarchical ((meso- and micro-) pores) structures attending to a more significant average pore sizes 21 , 26 .

Figure 4 N 2 adsorption–desorption isotherm of UAS MIL-53(Al).

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Facile Synthesis of Hierarchically Structured MIL-53(Al) With Superior Properties Using An Environmentally-Friendly Ultrasonic Method For Separating Lead Ions From Aqueous Solutions

“…The high crystallinity and porosity of the sample yield a high BET surface area of 1538.6 m2/g and a vast average pore size of 1.74 nm. BET surface area and average pore size are greater than those conventionally synthesized MIL-53(Al) introduced in the literature [20][21][22] ; it could be explained by the effect of ultrasound waves on the crystalline structure of MIL-53(Al). Ultrasonic intensity as a driving force ends up in a substantial quantity of cavitation bubbles, and increases in crystallinity, leading to a higher BET expanse in line with the XRD pattern discussed 18,23 .…”

“…Ultrasonic intensity as a driving force ends up in a substantial quantity of cavitation bubbles, and increases in crystallinity, leading to a higher BET expanse in line with the XRD pattern discussed 18,23 . Moreover, the high intensity of ultrasonic waves creates mesopores in the structure of MOFs 24 , leading to a hierarchical ((meso-and micro-) pores) structures attending to a more significant average pore sizes 20,25 . 1 Measured using t-plot method.…”