Application of metal − organic frameworks

The burgeoning field of metal-organic frameworks or porous coordination polymers has received increasing interest in recent years. In the last decade these microporous materials have found several applications including storage and separation of gases, sensors, catalysis and functional materials. In order to better design new metal-organic frameworks and porous coordination polymers with specific functionalities a fundamental issue is to achieve a basic understanding of the relationship between molecular parameters and structures, preferred adsorption sites and properties by using using modern theoretical methods. The focus of this mini-review is a description of the potential and emerging applications of metal-organic framework

Metal-organic framework based mixed matrix membranes: a solution for highly efficient CO2 capture?

The field of metal-organic framework based mixed matrix membranes (M(4)s) is critically reviewed, with special emphasis on their application in CO2 capture during energy generation. After introducing the most relevant parameters affecting membrane performance, we define targets in terms of selectivity and productivity based on existing literature on process design for pre- and post-combustion CO2 capture. Subsequently, the state of the art in M(4)s is reviewed against these targets. Because final application of these membranes will only be possible if thin separation layers can be produced, the latest advances in the manufacture of M-4 hollow fibers are discussed. Finally, the recent efforts in understanding the separation performance of these complex composite materials and future research directions are outlined.European Commission FP7 608490 ERC 33574

Facile synthesis of the DD3R zeolite : performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

Small pore size and hydrophobic nature of DD3R make this material a unique zeolite with high potential in industrial separation applications. However, the reproducible rapid synthesis of this zeolite is still a problem. In this work, a thorough assessment of different synthetic methods revealed that synthesis reproducibility relies on two main pillars: the use of properly cleaned autoclave liners and the synthesis composition. High quality DD3R crystals are obtained when KOH is used as a cleaning agent, eliminating memory effects, and when KF is used in the synthesis as a mineralizing agent. The effect of fluoride addition is investigated by use of several characterization techniques (13C, 19F and 29Si MAS-NMR and (2D) 29Si–1H correlation spectra), while monitoring the temporal crystallization of DDR. 29Si–1H NMR reveals that template molecules accommodated within the cages are sticking to these 8-ring windows through their amine group. High quality DD3R crystals are applied in the adsorptive separation of buta-1,3-diene and but-2-ene isomers, one of the most energy intensive separations in chemical industry. Mixture separation experiments revealed that the 8-ring apertures of the DD3R cages are only accessible to trans-but-2-ene and buta-1,3-diene, while excluding but-1-ene and cis-but-2-ene molecules, resulting in shape-selective separation in the presence of C4 mixtures

Small-angle X-ray scattering documents the growth of metal-organic frameworks

We present a combined in situ small- and wide-angle scattering (SAXS/WAXS) study on the crystallization of two topical metal-organic frameworks synthesized from similar metal and organic precursors: NH2-MIL-53(Al) and NH2-MIL-101(Al). A thorough analysis of SAXS data reveals the most important phenomena occurring during crystallization and unravels the effect of the solvent. NH2-MIL-53(Al) growth follows two routes: (i) through direct hydrolysis of AlCl3·6H2O in water, and (ii) via the intermediate NH2-MOF-235(Al), which forms in pure DMF or DMF/H2O mixtures. In the case of pure H2O as solvent, formation of NH2-MIL-53(Al) crystals proceeds through steady growth in all three dimensions. The addition of DMF to the synthesis mixture results in amorphous scattering entities forming very rapidly and subsequently arranging into the intermediate phase, NH2-MOF-235(Al). In DMF/H2O mixtures, amorphous precursors develop in rapid fashion with fractal character dominating, followed by densification, crystallization of NH2-MOF-235(Al) and slow transformation into NH2-MIL-53(Al). Formation of NH2-MIL-101(Al) only occurs when pure DMF is used as solvent, and it always proceeds through the formation of the intermediate NH2-MOF-235(Al). In this case a smooth scatterer surface is observed, with morphology and size constant in time. -------------------------------------------------------------------------------

Live encapsulation of a Keggin polyanion in NH2-MIL-101(Al) observed by in situ time resolved X-ray scattering

The templating effect of the Keggin polyanion derived from phosphotungstic acid (PTA) during the synthesis of NH2-MIL- 101(Al) has been investigated by means of in situ SAXS/WAXS. Kinetic analysis and structural observations demonstrate that PTA acts as a nucleation site and that it stabilizes the precursor phase NH2-MOF-235(Al). Surprisingly kinetics of formation are little changed

Small-angle X-ray scattering documents the growth of metal-organic frameworks

We present a combined in situ small- and wide-angle scattering (SAXS/WAXS) study on the crystallization of two topical metal-organic frameworks synthesized from similar metal and organic precursors: NH2-MIL-53(Al) and NH2-MIL-101(Al). A thorough analysis of SAXS data reveals the most important phenomena occurring during crystallization and unravels the effect of the solvent. NH2-MIL-53(Al) growth follows two routes: (i) through direct hydrolysis of AlCl3·6H2O in water, and (ii) via the intermediate NH2-MOF-235(Al), which forms in pure DMF or DMF/H2O mixtures. In the case of pure H2O as solvent, formation of NH2-MIL-53(Al) crystals proceeds through steady growth in all three dimensions. The addition of DMF to the synthesis mixture results in amorphous scattering entities forming very rapidly and subsequently arranging into the intermediate phase, NH2-MOF-235(Al). In DMF/H2O mixtures, amorphous precursors develop in rapid fashion with fractal character dominating, followed by densification, crystallization of NH2-MOF-235(Al) and slow transformation into NH2-MIL-53(Al). Formation of NH2-MIL-101(Al) only occurs when pure DMF is used as solvent, and it always proceeds through the formation of the intermediate NH2-MOF-235(Al). In this case a smooth scatterer surface is observed, with morphology and size constant in time. -------------------------------------------------------------------------------

Facile synthesis of the DD3R zeolite: performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

Small pore size and hydrophobic nature of DD3R make this material a unique zeolite with high potential in industrial separation applications. However, the reproducible rapid synthesis of this zeolite is still a problem. In this work, a thorough assessment of different synthetic methods revealed that synthesis reproducibility relies on two main pillars: the use of properly cleaned autoclave liners and the synthesis composition. High quality DD3R crystals are obtained when KOH is used as a cleaning agent, eliminating memory effects, and when KF is used in the synthesis as a mineralizing agent. The effect of fluoride addition is investigated by use of several characterization techniques (13C, 19F and 29Si MAS-NMR and (2D) 29Si–1H correlation spectra), while monitoring the temporal crystallization of DDR. 29Si–1H NMR reveals that template molecules accommodated within the cages are sticking to these 8-ring windows through their amine group. High quality DD3R crystals are applied in the adsorptive separation of buta-1,3-diene and but-2-ene isomers, one of the most energy intensive separations in chemical industry. Mixture separation experiments revealed that the 8-ring apertures of the DD3R cages are only accessible to trans-but-2-ene and buta-1,3-diene, while excluding but-1-ene and cis-but-2-ene molecules, resulting in shape-selective separation in the presence of C4 mixtures.status: publishe

Facile synthesis of the DD3R zeolite : performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

Small pore size and hydrophobic nature of DD3R make this material a unique zeolite with high potential in industrial separation applications. However, the reproducible rapid synthesis of this zeolite is still a problem. In this work, a thorough assessment of different synthetic methods revealed that synthesis reproducibility relies on two main pillars: the use of properly cleaned autoclave liners and the synthesis composition. High quality DD3R crystals are obtained when KOH is used as a cleaning agent, eliminating memory effects, and when KF is used in the synthesis as a mineralizing agent. The effect of fluoride addition is investigated by use of several characterization techniques (13C, 19F and 29Si MAS-NMR and (2D) 29Si–1H correlation spectra), while monitoring the temporal crystallization of DDR. 29Si–1H NMR reveals that template molecules accommodated within the cages are sticking to these 8-ring windows through their amine group. High quality DD3R crystals are applied in the adsorptive separation of buta-1,3-diene and but-2-ene isomers, one of the most energy intensive separations in chemical industry. Mixture separation experiments revealed that the 8-ring apertures of the DD3R cages are only accessible to trans-but-2-ene and buta-1,3-diene, while excluding but-1-ene and cis-but-2-ene molecules, resulting in shape-selective separation in the presence of C4 mixtures