Name: sulfate separation by selective crystallization with a bis-iminoguanidinium ligand
Uploaded: 2016-09-08T13:00:00
Description: Watch this Scientific Journal Video about Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand at JoVE.com

This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. We thank the University of North Carolina Wilmington for providing the seawater.

1. Synthesis of 1,4-Benzene-bis(iminoguanidinium) Chloride (BBIG-Cl)
<ol>
	<li>In Situ Synthesis of the 1,4-Benzene-bis(iminoguanidinium) Chloride Ligand (BBIG-Cl) and Its Crystallization with Sulfate
	<ol>
		<li>Add 0.067 g of terephthalaldehyde and 2.2 ml of a 0.5 M aqueous solution of aminoguanidinium chloride to 10 ml of deionized water in a 25 ml round bottom flask equipped with a magnetic stir bar.</li>
		<li>Stir the solution magnetically for four hours at 20 &#176;C. This will yield a slightly yellow s...

<ol>
	<li>Langton, M. L., Serpell, C. J., Beer, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anion+Recognition+in+Water:+Recent+Advances+from+Supramolecular+and+Macromolecular+Perspective.">Anion Recognition in Water: Recent Advances from Supramolecular and Macromolecular Perspective.</a> Angew. Chem. Int. Ed. 55, 1974-1987 (2016).</li><li>Busschaert, N., Caltagirone, C., Van Rossom, W., Gale, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+Supramolecular+Anion+Recognition.">Applications of Supramolecular Anion Recognition.</a> Chem. Rev. 115, 8038-8155 (2015).</li><li>Moyer, B. A., Custelcean, R., Hay, B. P., Sessler, J. L., Bowman-James, K., Day, V. W., Sung-Ok, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Case+for+Molecular+Recognition+in+Nuclear+Separations:+Sulfate+Separation+from+Nuclear+Wastes.">A Case for Molecular Recognition in Nuclear Separations: Sulfate Separation from Nuclear Wastes.</a> Inorg. Chem. 52, 3473-3490 (2013).</li><li>Kim, S. K., Lee, J., Williams, N. J., Lynch, V. M., Hay, B. P., Moyer, B. A., Sessler, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bipyrrole-Strapped+Calix[4]pyrroles:+Strong+Anion+Receptors+That+Extract+the+Sulfate+Anion.">Bipyrrole-Strapped Calix[4]pyrroles: Strong Anion Receptors That Extract the Sulfate Anion.</a> J. Am. Chem. Soc. 136, 15079-15085 (2014).</li><li>Jia, C., Wu, B., Li, S., Huang, X., Zhao, Q., Li, Q., Yang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+Efficient+Extraction+of+Sulfate+Ions+with+a+Tripodal+Hexaurea+Receptor.">Highly Efficient Extraction of Sulfate Ions with a Tripodal Hexaurea Receptor.</a> Angew. Chem. Int. Ed. 50, 486-490 (2011).</li><li>Rajbanshi, A., Moyer, B. A., Custelcean, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sulfate+Separation+from+Aqueous+Alkaline+Solutions+by+Selective+Crystallization+of+Alkali+Metal+Coordination+Capsules.">Sulfate Separation from Aqueous Alkaline Solutions by Selective Crystallization of Alkali Metal Coordination Capsules.</a> Cryst. Growth Des. 11, 2702-2706 (2011).</li><li>Custelcean, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Urea-Functionalized+Crystalline+Capsules+for+Recognition+and+Separation+of+Tetrahedral+Oxoanions.">Urea-Functionalized Crystalline Capsules for Recognition and Separation of Tetrahedral Oxoanions.</a> Chem. Commun. 49, 2173-2182 (2013).</li><li>Custelcean, R., Sloop, F. V., Rajbanshi, A., Wan, S., Moyer, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sodium+Sulfate+Separation+from+Aqueous+Alkaline+Solutions+via+Crystalline+Urea-Functionalized+Capsules:+Thermodynamics+and+Kinetics+of+Crystallization.">Sodium Sulfate Separation from Aqueous Alkaline Solutions via Crystalline Urea-Functionalized Capsules: Thermodynamics and Kinetics of Crystallization.</a> Cryst. Growth Des. 15, 517-522 (2015).</li><li>Custelcean, R., Williams, N. J., Seipp, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aqueous+Sulfate+Separation+by+Crystallization+of+Sulfate-Water+Clusters.">Aqueous Sulfate Separation by Crystallization of Sulfate-Water Clusters.</a> Angew. Chem. Int. Ed. 54, 10525-10529 (2015).</li><li>Custelcean, R., Williams, N. J., Seipp, C. A., Ivanov, A. S., Bryantsev, V. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aqueous+Sulfate+Separation+by+Sequestration+of+[(SO4)(H2O)4]4-+Clusters+within+Highly+Insoluble+Imine-Linked+Bis-Guanidinium+Crystals.">Aqueous Sulfate Separation by Sequestration of [(SO4)(H2O)4]4- Clusters within Highly Insoluble Imine-Linked Bis-Guanidinium Crystals.</a> Chem. Eur. J. 22, 1997-2003 (2016).</li><li>Khownium, K., Wood, S. J., Miller, K. A., Balakrishna, R., Nguyen, T. B., Kimbrell, M. R., Georg, G. I., David, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+Endotoxin-Sequestering+Compounds+with+Terephthaldehyde-bis-guanylhydrazone+Scaffolds.">Novel Endotoxin-Sequestering Compounds with Terephthaldehyde-bis-guanylhydrazone Scaffolds.</a> Bioorg. Med. Chem. Lett. 16, 1305-1308 (2006).</li><li>Pecharsky, V. K., Zavalij, P. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fundamentals of Powder Diffraction and Structural Characterization of Materials. , (2005).</li><li>Goldenberg, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Principles of NMR Spectroscopy: An Illustrated Guide. , (2016).</li></ol>

This technique is rather tolerant to many deviations from the written procedure, which makes it quite robust. There are however two critical steps that must be followed. First, the BBIG-Cl ligand needs to be as pure as possible. Impurities will not only affect the crystallization and the solubility of the resulting sulfate salt, but will also make it difficult to calculate the amount required for quantitative sulfate removal from solution. Second, all steps in the &#946; liquid scintillation counting section need to be f...

Selective separation of hydrophilic oxoanions (e.g., sulfate, chromate, phosphate) from competitive aqueous solutions represents a fundamental challenge with relevance to environmental remediation, energy production, and human health.1,2 Sulfate in particular is difficult to extract from water due to its intrinsic reluctance to shed its hydration sphere and migrate into less polar environments.3 Making aqueous sulfate extraction more efficient typically requires complex receptors that are difficult and tedious to synthesize and purify, often involving toxic reagents and solvents.4,5
Selective crystallization offers a simple yet effective alternative to sulfate separation from water.6-9 Though some metal cations such as Ba2+, Pb2+, or Ra2+ form very insoluble sulfate salts, their use in sulfate separation is not always practical due to their high toxicity and sometimes-low selectivity. Employing organic ligands as sulfate precipitants takes advantage of the structural diversity and amenability to design characteristic to organic molecules. An ideal organic ligand for aqueous sulfate crystallization should be soluble in water, yet form an insoluble sulfate salt or complex in a relatively short time and in the presence of high concentrations of competing ions. Additionally, it should be easy to synthesize and recycle. One such a ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), self-assembled in situ from two commercially available precursors, terephthalaldehyde and aminoguanidinium chloride, was recently found to be extremely effective in aqueous sulfate separation.10 The ligand is water-soluble in the chloride form, and selectively crystallizes with sulfate into an extremely insoluble salt that can be easily removed from solution by simple filtration. The BBIG ligand can then be recovered by deprotonation with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into the chloride form with aqueous HCl, and reused in another separation cycle. The efficacy of this ligand in removing sulfate from water is so great that monitoring the remaining sulfate concentration in solution is no longer a trivial task, requiring a more advanced technique that allows accurate measurement of trace amounts of the anion. For this purpose, radiolabeled 35S sulfate tracer in conjunction with &#946; liquid scintillation counting was employed, a technique commonly utilized in liquid-liquid extractive separations, and recently demonstrated to be effective in monitoring sulfate crystallization.8
This protocol demonstrates the one-pot in situ synthesis of the BBIG ligand and its crystallization as the sulfate salt from aqueous solutions. The ex situ synthesis of the ligand11 is also presented as a convenient method for the production of larger amounts of BBIG-Cl, which can be stored in the crystalline form until ready to use. Sulfate removal from seawater using the previously prepared BBIG-Cl ligand is then demonstrated. Finally, the use of 35S-labeled sulfate and &#946; liquid scintillation counting for measuring the sulfate concentration in seawater is demonstrated. This protocol is intended to provide a tutorial for those broadly interested in exploring the use of selective crystallization for aqueous anion separation.

<table border="0" cellpadding="0" cellspacing="0" width="740">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Terephthalaldehyde</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">T2207</td>
			<td style="width:313px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Aminoguanidinium Chloride</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">#396494</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium Sulfate</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">#239313</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Barium Chloride</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">#342920</td>
			<td>Highly Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethanol</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;"></td>
			<td>Reagent Grade (190 proof)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium Hydroxide</td>
			<td style="width:92px;">EMD</td>
			<td style="width:119px;">SX0590-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hydrochloric Acid</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">#258148</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Filter Paper</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;">-</td>
			<td>Any qualitative or analytical filter paper will work</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Syringe Filter (0.22 um)</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;">-</td>
			<td>Nylon filter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">35S Labeled Sulfate</td>
			<td style="width:92px;">Perkin Elmer</td>
			<td style="width:119px;">NEX041005MC</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ultima Gold Scintillation Cocktail</td>
			<td style="width:92px;">Perkin Elmer</td>
			<td style="width:119px;">#6013329</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Polypropylene Vials&#160;</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;">-</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Disposable Syringe (2-3 mL)</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;">-</td>
			<td>Any disposable plastic syringe works</td>
		</tr>
	</tbody>
</table>

sulfate separation by selective crystallization with a bis-iminoguanidinium ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

The powder X-ray diffraction pattern of BBIG-SO4 (Figure 1) allows for unambiguous confirmation of the identity of the crystallized solid. In comparing the obtained pattern versus the reference one, peak intensity matters less than peak positioning. All strong peaks shown in the reference should be present in the obtained sample. The appearance of strong peaks in the sample that are absent in the reference pattern indicates the presence of impurities.
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Watch this Scientific Journal Video about Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand at JoVE.com

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

The overall goal of this procedure is to separate the sulfate anions from competitive aqueous solutions by selective crystallization with a bis-guanidinium ligand synthesized in a single step from simple precursors.Sulfate separation from competitive aqueous solutions is challenging due to the strong hydrophilic nature of this anion and typically requires complex receptors that are difficult to synthesize and purify.The main advantage of this technique is that it combines the in situ ligand synthesis and anion separation into a single step.To begin the in situ procedure, add 10 milliliters of deionized water to a round-bottomed flask equipped with a magnetic stir bar.Then add 067 grams of terephthalaldehyde and 2.2 milliliters of a 0.5 molar aqueous solution of aminoguanidinium chloride.Stir the solution for four hours at 20 degrees Celsius.This will yield a slightly yellow solution of BIG chloride.Once the stirring is complete, add 0.5 milliliters of a one molar aqueous solution of sodium sulfate.This will precipitate out 1, 4 benzene bis aminoguanidinium sulfate as a crystalline white solid.Next, utilize vacuum filtration to recover the BIG sulfate.Wash the recovered solid on the filter paper five times with five milliliter aliquots of water to obtain the pure sulfate salt.Using powder x-ray defraction, check the phase purity of the crystalline BIG sulfate as described.For ex situ synthesis, first set up a 50 milliliter round-bottomed flash with a stir bar and hot plate.Add 20 milliliters of ethanol.Next, add four grams of terepthalaldehyde and 7.26 grams of aminoguanidinium chloride.Heat the solution to 60 degrees Celsius and stir it for two hours.Then cool the solution to 20 degrees Celsius and let it rest for three hours.Utilize a filter paper-equipped B

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The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used the ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer by generating a charged structure provides an opportunity to use extraction as a simple purification technique. By combining the use of a miscible organic solvent with saturated sodium bisulfite, aldehydes and reactive ketones can be successfully transformed into charged bisulfite adducts that can then be separated from other organic components of a mixture by the introduction of an immiscible organic layer. Here, we describe a simple protocol for the removal of aldehydes, including sterically-hindered neopentyl aldehydes and some ketones, from chemical mixtures. Ketones can be separated if they are sterically unhindered cyclic or methyl ketones. For aliphatic aldehydes and ketones, dimethylformamide is used as the miscible solvent to improve removal rates. The bisulfite addition reaction can be reversed by basification of the aqueous layer, allowing for the re-isolation of the reactive carbonyl component of a mixture.

Here, we present a protocol to remove aldehydes and reactive ketones from mixtures by a liquid-liquid extraction protocol directly with saturated sodium bisulfite in a miscible solvent. This combined protocol is rapid and facile to perform. The aldehyde or ketone can be re-isolated by the basification of the aqueous layer.

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer ...

Analyzing Protein Architectures and Protein-Ligand Complexes by Integrative Structural Mass Spectrometry

Proteins are an important class of biological macromolecules that play many key roles in cellular functions including gene expression, catalyzing metabolic reactions, DNA repair and replication. Therefore, a detailed understanding of these processes provides critical information on how cells function. Integrative structural MS methods offer structural and dynamical information on protein complex assembly, complex connectivity, subunit stoichiometry, protein oligomerization and ligand binding. Recent advances in integrative structural MS have allowed for the characterization of challenging biological systems including large DNA binding proteins and membrane proteins. This protocol describes how to integrate diverse MS data such as native MS and ion mobility-mass spectrometry (IM-MS) with molecular dynamics simulations to gain insights into a helicase-nuclease DNA repair protein complex. The resulting approach provides a framework for detailed studies of ligand binding to other protein complexes involved in important biological processes.

Mass spectrometry (MS) has emerged as an important tool for the investigation of structure and dynamics of macromolecular assemblies. Here, we integrate MS-based approaches to interrogate protein complex formation and ligand binding.

Proteins are an important class of biological macromolecules that play many key roles in cellular functions including gene expression, catalyzing ...

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...