Ethane/Ethylene Separations in Flexible Diamondoid Coordination Networks via an Ethane-Induced Gate-Opening Mechanism.

Separating ethane (CH) from ethylene (CH) is an essential and energy-intensive process in the chemical industry. Here, we report two flexible diamondoid coordination networks, and , that exhibit gate-opening between narrow-pore (NP) and large-pore (LP) phases for CH, but not for CH. thereby exhibited a type F-IV isotherm at 273 K with no CH uptake and a high uptake (111 cm g, 1 atm) for the NP and LP phases, respectively.

Hydrogen bond unlocking-driven pore structure control for shifting multi-component gas separation function.

Purification of ethylene (CH) as the most extensive and output chemical, from complex multi-components is of great significance but highly challenging. Herein we demonstrate that precise pore structure tuning by controlling the network hydrogen bonds in two highly-related porous coordination networks can shift the efficient CH separation function from CH/CH/CH ternary mixture to CO/CH/CH/CH quaternary mixture system. Single-crystal X-ray diffraction revealed that the different amino groups on the triazolate ligands resulted in the change of the hydrogen bonding in the host network, which led to changes in the pore shape and pore chemistry.

An aliphatic MOF with a molecular sieving effect for efficient CH/CH separation.

A metal-organic framework, SDMOF-1, with rigid pores of about 3.4 Å, which is appropriate for accommodating CH molecules, exhibits high CH adsorption capacity and great separation capability of the CH/CH mixture. This work provides a new method to design aliphatic MOFs with a molecular sieving effect to realize efficient gas separation.

Crystal Engineering of Two Light and Pressure Responsive Physisorbents.

An emerging strategy in the design of efficient gas storage technologies is the development of stimuli-responsive physisorbents which undergo transformations in response to a particular stimulus, such as pressure, heat or light. Herein, we report two isostructural light modulated adsorbents (LMAs) containing bis-3-thienylcyclopentene (BTCP), LMA-1 [Cd(BTCP)(DPT) ] (DPT=2,5-diphenylbenzene-1,4-dicarboxylate) and LMA-2 [Cd(BTCP)(FDPT) ] (FDPT=5-fluoro-2,diphenylbenzene-1,4-dicarboxylate). Both LMAs undergo pressure induced switching transformations from non-porous to porous via adsorption of N , CO and C H .

Reversible transformations between the non-porous phases of a flexible coordination network enabled by transient porosity.

Flexible metal-organic materials that exhibit stimulus-responsive switching between closed (non-porous) and open (porous) structures induced by gas molecules are of potential utility in gas storage and separation. Such behaviour is currently limited to a few dozen physisorbents that typically switch through a breathing mechanism requiring structural contortions. Here we show a clathrate (non-porous) coordination network that undergoes gas-induced switching between multiple non-porous phases through transient porosity, which involves the diffusion of guests between discrete voids through intra-network distortions.

Highly Robust Microporous Metal-Organic Frameworks for Efficient Ethylene Purification under Dry and Humid Conditions.

Two C H -selective metal-organic framework (MOF) adsorbents with ultrahigh stability, high surface areas, and suitable pore size have been designed and synthesized for one-step separation of ethane/ethylene (C H /C H ) under humid conditions to produce polymer-grade pure C H . Experimental results reveal that these two MOFs not only adsorb a high amount of C H but also display good C H /C H selectivity verified by fixed bed column breakthrough experiments. Most importantly, the good water stability and hydrophobic pore environments make these two MOFs capable of efficiently separating C H /C H under humid conditions, exhibiting the benchmark performance among all reported adsorbents for separation of C H /C H under humid conditions.

Significantly Enhanced Carbon Dioxide Selective Adsorption via Gradual Acylamide Truncation in MOFs: Experimental and Theoretical Research.

A gradual amide truncation strategy was presented to tune the pore chemistry and CO capture performance of a series of tetracarboxylate-based Cu-MOFs. These MOFs exhibited a high density of Lewis basic sites (LBSs) and open metal sites and were prepared with the goal to enhance CO selective adsorption capacity. [Cu(L1)(HO)] (: NJU-Bai for Nanjing University Bai's group), [Cu(L2) (HO)] (), and [Cu(L)(HO)] (: NTUniv for Nantong University) were synthesized, and we observed that the CO adsorption capacities and MOF structures were impacted by subtle changes in ligands.

Investigating H Adsorption in Isostructural Metal-Organic Frameworks M-CUK-1 (M = Co and Mg) through Experimental and Theoretical Studies.

A combined experimental and theoretical study of H adsorption was carried out in Co-CUK-1 and Mg-CUK-1, two isostructural metal-organic frameworks (MOFs) that consist of M ions (M = Co and Mg) coordinated to pyridine-2,4-dicarboxylate (pdc) and OH ligands. These MOFs possess saturated metal centers in distorted octahedral environments and narrow pore sizes and display high chemical and thermal stability. Previous experimental studies revealed that Co-CUK-1 exhibits a H uptake of 183 cm g at 77 K/1.

Self-Adjusting Metal-Organic Framework for Efficient Capture of Trace Xenon and Krypton.

The capture of the xenon and krypton from nuclear reprocessing off-gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, the development of high-performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the nuclear reprocessing off-gas conditions remains challenging. Herein, we report a self-adjusting metal-organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off-gas.

Metal-Organic Framework Based Hydrogen-Bonding Nanotrap for Efficient Acetylene Storage and Separation.

The removal of carbon dioxide (CO) from acetylene (CH) is a critical industrial process for manufacturing high-purity CH. However, it remains challenging to address the tradeoff between adsorption capacity and selectivity, on account of their similar physical properties and molecular sizes. To overcome this difficulty, here we report a novel strategy involving the regulation of a hydrogen-bonding nanotrap on the pore surface to promote the separation of CH/CO mixtures in three isostructural metal-organic frameworks (MOFs, named MIL-160, CAU-10H, and CAU-23, respectively).

Tuning the Selectivity between CH and CO in Molecular Porous Materials.

A combined experimental and theoretical study of CH and CO adsorption and separation was performed in two isostructural molecular porous materials (MPMs): ([Cu(adenine)Cl]Cl) and ([Cu(adenine)(TiF)]). It was revealed that displayed higher low-pressure uptake, isosteric heat of adsorption (), and selectivity for CH than CO, whereas the opposite was observed for . While contains only one type of accessible channel, which has a greater preference toward CH, contains three distinct accessible channels, one of which is a confined region between two large channels that represents the primary binding site for both adsorbates.

One-step ethylene production from a four-component gas mixture by a single physisorbent.

One-step adsorptive purification of ethylene (CH) from four-component gas mixtures comprising acetylene (CH), ethylene (CH), ethane (CH) and carbon dioxide (CO) is an unmet challenge in the area of commodity purification. Herein, we report that the ultramicroporous sorbent Zn-atz-oba (Hoba = 4,4-dicarboxyl diphenyl ether; Hatz = 3-amino-1,2,4-triazole) enables selective adsorption of CH, CH and CO over CH thanks to the binding sites that lie in its undulating pores. Molecular simulations provide insight into the binding sites in Zn-atz-oba that are responsible for coadsorption of CH, CH and CO over CH.

Efficient propyne/propadiene separation by microporous crystalline physiadsorbents.

Selective separation of propyne/propadiene mixture to obtain pure propadiene (allene), an essential feedstock for organic synthesis, remains an unsolved challenge in the petrochemical industry, thanks mainly to their similar physicochemical properties. We herein introduce a convenient and energy-efficient physisorptive approach to achieve propyne/propadiene separation using microporous metal-organic frameworks (MOFs). Specifically, HKUST-1, one of the most widely studied high surface area MOFs that is available commercially, is found to exhibit benchmark performance (propadiene production up to 69.

Toward an Understanding of the Propensity for Crystalline Hydrate Formation by Molecular Compounds. Part 2.

The propensity of molecular organic compounds to form stoichiometric or nonstoichiometric crystalline hydrates remains a challenging aspect of crystal engineering and is of practical relevance to fields such as pharmaceutical science. In this work, we address the propensity for hydrate formation of a library of eight compounds comprised of 5- and 6-membered -heterocyclic aromatics classified into three subgroups: linear dipyridyls, substituted Schiff bases, and tripodal molecules. Each molecular compound studied possesses strong hydrogen bond acceptors and is devoid of strong hydrogen bond donors.

Molecular Sieving of Acetylene from Ethylene in a Rigid Ultra-microporous Metal Organic Framework.

Rigid molecular sieving materials are the ideal candidates for gas separation (e. g., C H /C H ) due to their ultrahigh adsorption selectivity and the absence of gas co-adsorption.

Nanospace Engineering of Metal-Organic Frameworks through Dynamic Spacer Installation of Multifunctionalities for Efficient Separation of Ethane from Ethane/Ethylene Mixtures.

Herein, a dynamic spacer installation (DSI) strategy has been implemented to construct a series of multifunctional metal-organic frameworks (MOFs), LIFM-61/31/62/63, with optimized pore space and pore environment for ethane/ethylene separation. In this respect, a series of linear dicarboxylic acids were deliberately installed in the prototype MOF, LIFM-28, leading to a dramatically increased pore volume (from 0.41 to 0.

Amino-Functionalised Hybrid Ultramicroporous Materials that Enable Single-Step Ethylene Purification from a Ternary Mixture.

Pyrazine-linked hybrid ultramicroporous (pore size <7 Å) materials (HUMs) offer benchmark performance for trace carbon capture thanks to strong selectivity for CO over small gas molecules, including light hydrocarbons. That the prototypal pyrazine-linked HUMs are amenable to crystal engineering has enabled second generation HUMs to supersede the performance of the parent HUM, SIFSIX-3-Zn, mainly through substitution of the metal and/or the inorganic pillar. Herein, we report that two isostructural aminopyrazine-linked HUMs, MFSIX-17-Ni (17=aminopyrazine; M=Si, Ti), which we had anticipated would offer even stronger affinity for CO than their pyrazine analogs, unexpectedly exhibit reduced CO affinity but enhanced C H affinity.

Pore Engineering for One-Step Ethylene Purification from a Three-Component Hydrocarbon Mixture.

Ethylene production from C2 hydrocarbon mixtures through one separation step is desirable but challenging because of the similar size and physical properties of acetylene, ethylene, and ethane. Herein, we report three new isostructural porous coordination networks (, , ; NPU represents Northwestern Polytechnical University) that are sustained by 9-connected nodes based upon a hexanuclear metal cluster of composition [Mn(μ-O)(CHCOO)]. exhibit a dual cage structure that was systematically fine-tuned in terms of cage size to realize selective adsorption of CH and CH over CH.

A MOF-based Ultra-Strong Acetylene Nano-trap for Highly Efficient C H /CO Separation.

Porous materials with open metal sites have been investigated to separate various gas mixtures. However, open metal sites show the limitation in the separation of some challenging gas mixtures, such as C H /CO . Herein, we propose a new type of ultra-strong C H nano-trap based on multiple binding interactions to efficiently capture C H molecules and separate C H /CO mixture.

Synergistic sorbent separation for one-step ethylene purification from a four-component mixture.

Purification of ethylene (CH), the largest-volume product of the chemical industry, currently involves energy-intensive processes such as chemisorption (CO removal), catalytic hydrogenation (CH conversion), and cryogenic distillation (CH separation). Although advanced physisorbent or membrane separation could lower the energy input, one-step removal of multiple impurities, especially trace impurities, has not been feasible. We introduce a synergistic sorbent separation method for the one-step production of polymer-grade CH from ternary (CH/CH/CH) or quaternary (CO/CH/CH/CH) gas mixtures with a series of physisorbents in a packed-bed geometry.

Molecular Sieving and Direct Visualization of CO in Binding Pockets of an Ultramicroporous Lanthanide Metal-Organic Framework Platform.

Inspired by the structure of carbonic anhydrase, we developed a robust ultramicroporous lanthanide metal-organic framework (MOF) platform (NKMOF-3-Ln), which possesses a porous pocket to selectively bind with CO at ambient conditions. Notably, CO molecules can be precisely observed in the single-crystal structure of NKMOF-3-Ln. Highly ordered CO molecules can strongly interact with the framework via electrostatic interaction of nitrates.

A Metal-Organic Framework Based Methane Nano-trap for the Capture of Coal-Mine Methane.

As a major greenhouse gas, methane, which is directly vented from the coal-mine to the atmosphere, has not yet drawn sufficient attention. To address this problem, we report a methane nano-trap that features oppositely adjacent open metal sites and dense alkyl groups in a metal-organic framework (MOF). The alkyl MOF-based methane nano-trap exhibits a record-high methane uptake and CH /N selectivity at 298 K and 1 bar.

Robust Microporous Metal-Organic Frameworks for Highly Efficient and Simultaneous Removal of Propyne and Propadiene from Propylene.

Simultaneous removal of trace amounts of propyne and propadiene from propylene is an important but challenging industrial process. We report herein a class of microporous metal-organic frameworks (NKMOF-1-M) with exceptional water stability and remarkably high uptakes for both propyne and propadiene at low pressures. NKMOF-1-M separated a ternary propyne/propadiene/propylene (0.