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Herein we report novel mesoporous zirconium-based metal-organic frameworks (MOFs) with zeolitic sodalite (sod) topology. Zr-sod-ZMOF-1 and -2 are constructed based on a novel cantellation design strategy. Distinctly, organic linkers are judiciously designed in order to promote the deployment of the 12-coordinated Zr hexanuclear molecular building block (MBB) as a tetrahedral secondary building unit, a prerequisite for zeolite-like nets. The resultant Zr-sod-ZMOFs exhibit mesopores with a diameter up to ≈43 A, while the pore volume of 1.98 cm3·g-1 measured for Zr-sod-ZMOF-1 is the highest reported experimental value for zeolite-like MOFs based on MBBs as tetrahedral nodes.

Developing the competence of molecular sorbents for energy-saving applications, such as C8 separations, requires efficient, stable, scalable, and easily recyclable materials that can readily transition to commercial implementation. Herein, we report an azobenzene-based cage for the selective separation of p-xylene isomer across a range of C8 isomers in both vapor and liquid states with selectivity that is higher than the reported all-organic sorbents. The crystal structure shows non-porous cages that are separated by p-xylene molecules through selective CH-π interactions between the azo bonds and the methyl hydrogen atoms of the xylene molecules. This cage is stable in solution and can be regenerated directly under vacuum to be used in multiple cycles. We envisage that this work will promote the investigation of the azo bond as well as guest-induced crystal-to-crystal phase transition in non-porous organic solids for energy-intensive separations.

Summary Chemical separations are of prime industrial importance; however, they consume a large portion of total industrial energy. Credibly, adsorbent-based separation methods offer the prospective to drastically lessen the energy demand of conventional energy-intensive separation processes. Prominently, a special class of porous materials, namely metal-organic frameworks (MOFs), are reasonably positioned to address various demanding separations in an energy-efficient manner. Out of a myriad of possible topologies for the construction of MOFs, face-transitive nets affording a sole type of window, preferably defined by three- or four-membered rings, can be regarded as ideal blueprints for the construction of MOFs for targeted separations. Intricate separations by MOFs based on some of these topologies are discussed, highlighting the effect of appropriate pore aperture and channel size with prerequisite functional groups on their separation performance. MOFs based on face-transitive nets offer great potential as effective fillers for the construction of practical mixed-matrix membranes (MMMs) with improved separation properties over conventional polymeric membranes.

Organic field-effect transistors (OFETs) are emerging as competitive candidates for gas sensing applications due to the ease of their fabrication process combined with the ability to readily fine-tune the properties of organic semiconductors. Nevertheless, some key challenges remain to be addressed, such as material degradation, low sensitivity, and poor selectivity toward toxic gases. Appropriately, a heterojunction combination of different sensing layers with multifunctional capabilities offers great potential to overcome these problems. Here, a novel and highly sensitive receptor layer is proposed encompassing a porous 3D metal-organic framework (MOF) based on isostructural-fluorinated MOFs acting as an NO2 specific preconcentrator, on the surface of a stable and ultrathin PDVT-10 organic semiconductor on an OFET platform. Here, with this proposed combination we have unveiled an unprecedented 700% increase in sensitivity toward NO2 analyte in contrast to the pristine PDVT-10. The resultant combination for this OFET device exhibits a remarkable lowest detection limit of 8.25 ppb, a sensitivity of 680 nA/ppb, and good stability over a period of 6 months under normal laboratory conditions. Further, a negligible response (4.232 nA/%RH) toward humidity in the range of 5%-90% relative humidity was demonstrated using this combination. Markedly, the obtained results support the use of the proposed novel strategy to achieve an excellent sensing performance with an OFET platform.

We apply molecular simulations to screen a database of reported metal-organic framework structures from the computation-ready, experimental (CoRE) MOF database to identify materials potentially capable of separating propane and propene by diffusion. We report a screening workflow that uses descriptor analysis, conventional molecular dynamics (MD), and Nudged Elastic Band (NEB) energy barrier calculations at both classical force field and Density Functional Theory (DFT) levels. For the first time, the effects of framework flexibility on guest transport properties were fully considered in a screening process and led to the identification of candidate MOFs. The hits identified by this proof-of-concept workflow include ZIF-8 and ZIF-67 previously shown to have large differences in propane and propene diffusivities as well as two other materials that have not been tested experimentally yet. This work emphasises the importance of taking into account framework flexibility when studying guest transport in porous materials, demonstrates the potential of the data-driven identification of high-performance materials and highlights the ways of improving the predictive power of the screening workflow.

Summary Metal-organic frameworks (MOFs) have attracted significant attention as sorbents for low-energy separation of CO2 from flue gas. Herein, we report the use of an interpenetration approach to developing a fluorinated MOF with the appropriate pore system to enable the efficient capture of CO2 from flue gas at 298 K. The MOF, dptz-CuTiF6, exhibits excellent volumetric and gravimetric CO2 uptakes at 10% CO2 and 298 K, which are superior to those of the reference aqueous amine technique, with significantly lower energy input for regeneration (38 kJ mol−1 versus 105 kJ mol−1). In cyclic breakthrough experiments, dptz-CuTiF6 achieves complete CO2 desorption at 298 K under inert gas purging. Single-crystal X-ray diffraction studies demonstrate that the exceptional CO2 adsorption capacity, moderate CO2 heat of adsorption, and high CO2-N2 selectivity are due to the optimal packing of the CO2 molecules within the MOF as well as the favorable thermodynamics and kinetics from cooperative host-guest interactions.

In this work, the reticular chemistry approach was implemented on a very stable ultra-microporous fluorinated MFFIVE-1-Ni MOFs to unveil the effect of subtle changes of the structure-employment of different fluorinated inorganic block on the adsorption of C2H2, C2H4 and CO2. A series of variable temperature single C2H2, C2H4 and CO2 adsorption isotherms and mixed gas adsorption column breakthrough experiments for different C2H2/C2H4 and CO2/C2H2 gas pair systems were carried out on the two isoreticular NbOFFIVE-1-Ni and AlFFIVE-1-Ni, containing respectively [NbOF5]2− and [AlF5]2− inorganic building blocks. The introduction of potential open metal site in a very confined pores led to favoring interaction of C2H2 but lowering the interaction with CO2, which resulted in enhancement of C2H2/C2H4 selectivity at low C2H2 concentration but a decrease in CO2/C2+ selectivity. The comparison of the C2H2/C2H4 and CO2/C2H2 separation performances with the structures of the MFFIVE-1-Ni MOFs provides useful information to shed light on the relationship between the structural features of this MOF platform and C2H2/C2H4 and CO2/C2H2 separation properties. This is a critical step in the wanted rational discovery/design of materials with enhanced performances for C2H2 recovery from C2H4 and CO2 at different concentration and having different level of input energy for recycling.

Conventional materials for gas/vapor sensing are limited to a single probe detection ability for specific analytes. However, materials capable of concurrent detection of two different probes in their respective harmful levels and using two types of sensing modes have yet to be explored. In particular, the concurrent detection of uncomfortable humidity levels and CO2 concentration (400–5000 ppm) in confined spaces is of extreme importance in a great variety of fields, such as submarine technology, aerospace, mining, and rescue operations. Herein, we report the deliberate construction and performance assessment of extremely sensitive sensors using an interdigitated electrode (IDE)-based capacitor and a quartz crystal microbalance (QCM) as transducing substrates. The unveiled sensors are able to simultaneously detect CO2 within the 400–5000 ppm range and relative humidity levels below 40 and above 60%, using two fluorinated metal–organic frameworks, namely, NbOFFIVE-1-Ni and AlFFIVE-1-Ni, fabricated as a thi...

The separation of styrene (ST) and ethylbenzene (EB) mixtures is of great importance in the petrochemical and plastics industries. Current technology employs multiple cycles of energy-intensive distillation due to the very close boiling points of ST and EB. Here, we show that the molecular sieving properties of easily scalable and stable trianglimine crystals offer ultrahigh selectivity (99%) for styrene separation. The unique molecular sieving properties of trianglimine crystals are corroborated by DFT calculations, suggesting that the incorporation of the nonplanar EB requires a significant deformation of the macrocyclic cavity whereas the planar ST can be easily accommodated in the cavity.

Energy-efficient approaches to propylene/propane separation such as molecular sieving are of considerable importance for the petrochemical industry. The metal organic framework NbOFFIVE-1-Ni adsorbs propylene but not propane at room temperature and atmospheric pressure, whereas the isostructural SIFSIX-3-Ni does not exclude propane under the same conditions. The static dimensions of the pore openings of both materials are too small to admit either guest, signalling the importance of host dynamics for guest entrance to and transport through the channels. We use ab initio calculations together with crystallographic and adsorption data to show that the dynamics of the two framework-forming units, polyatomic anions and pyrazines, govern both diffusion and separation. The guest diffusion occurs by opening of the flexible window formed by four pyrazines. In NbOFFIVE-1-Ni, (NbOF5)2− anion reorientation locates propane away from the window, which enhances propylene/propane separation., Porous materials acting as molecular sieves for propylene/propane separation are important for the petrochemical industry. Here the authors show an example of how specific guest-host interactions can result in structural changes in the porous host and shut down diffusion of one of the two similar guest molecules.

Development of advanced CO2 capture physical adsorbents in powdered form is a key step, nevertheless their transformation into particulates is a process of paramount importance for their deployment...

The discovery of appropriate synthetic reaction conditions for fabricating a stable zirconium-based molecular sieve (Zr-fum-fcu-MOF) with minimal defects and its utilization in the challenging separation of linear paraffins from branched paraffins is reported. The crystallinity and structural defects were modulated and adjusted at the molecular level by controlling the synthetic reaction conditions (i.e., amounts of modulators and ligands). The impact of molecular defects on the separation of n-butane from iso-butane was studied through the preparation, fine characterization, and performance evaluation of Zr-fum-fcu-MOFs with varying degrees of defects. Defect-rich Zr-fum-fcu-MOFs were found to have poor n-butane/iso-butane separation, mainly driven by thermodynamics, while Zr-fum-fcu-MOFs with fewer or minimal defects showed efficient separation, driven mainly by kinetics and full molecular exclusion mechanisms. The impact of intrinsic defects (i.e., missing organic or inorganic blocks) on the associated mechanisms involved in the separation of n-butane/iso-butane was evidenced through single-gas adsorption, mixed-gas column breakthrough experiments, and calorimetric studies. This investigation demonstrates, for the first time, the importance of controlling intrinsic defects to maintain the selective exclusion behavior of hydrocarbon isomers when using molecular sieves.

The process used to upgrade natural gas, biogas and refinery-off-gas directly influences the cost of producing the fuel and often requires complex separation strategies and operational systems to remove contaminants such as hydrogen sulfide (H2S) and carbon dioxide (CO2). Here we report a fluorinated metal–organic framework (MOF), AlFFIVE-1-Ni, that allows simultaneous and equally selective removal of CO2 and H2S from CH4-rich streams in a single adsorption step. The simultaneous removal is possible for a wide range of H2S and CO2 compositions and concentrations of the gas feed. Pure component and mixed gas adsorption, single-crystal X-ray diffraction and molecular simulation studies were carried out to elucidate the mechanism governing the simultaneous adsorption of H2S and CO2. The results suggest that concurrent removal of CO2 and H2S is achieved via the integrated favourable sites for H2S and CO2 adsorption in a confined pore system. This approach offers the prospect of simplifying the complex schemes for removal of acid gases. Contaminants such as CO2 and H2S present in natural gas and biogas streams must be removed before use; existing strategies to do so can be rather complex. Here, the authors use a fluorinated porous metal–organic framework to remove CO2 and H2S from CH4-rich feeds in a single step, potentially simplifying the process.

Here we introduce for the first time a metal-free trianglamine-based supramolecular organic framework, T-SOF-1, with permanent intrinsic porosity and high affinity to CO2. The capability of tuning the pore aperture dimensions is also demonstrated by molecular guest encapsulation to afford excellent CO2/CH4 separation for natural gas upgrading.

Summary Hydrolytically stable adsorbents, with notable water uptake, are of prime importance and offer great potential for many water-adsorption-related applications. Nevertheless, deliberate construction of tunable porous solids with high porosity and high stability remains challenging. Here, we present the successful deployment of reticular chemistry to address this demand: we constructed Cr- soc -MOF-1, a chemically and hydrolytically stable chromium-based metal-organic framework (MOF) with underlying soc topology. Prominently, Cr- soc -MOF-1 offers the requisite thermal and chemical stability concomitant with unique adsorption properties, namely extraordinary high porosity (apparent surface area of 4,549 m 2 /g) affording a water vapor uptake of 1.95 g/g at 70% relative humidity. This exceptional water uptake is maintained over more than 100 adsorption-desorption cycles. Markedly, the adsorbed water can be fully desorbed by just the simple reduction of the relative humidity at 25°C. Cr- soc -MOF-1 offers great potential for use in applications pertaining to water vapor control in enclosed and confined spaces and dehumidification.

A series of porous organic polymers (POPs) were synthesized using tetrahedral 1,3,5,7-tetracyanoadamantane as the main building block. The POP frameworks in the presence of different amounts of molten ZnCl2 as an ionic liquid were allowed to alter/enhance the Brunauer–Emmett–Teller (BET) surface areas of the POPs in the range from 760 to 1560 m2 g−1. The mechanism of the carbonization was unveiled by IR, EA and solid-state NMR; which is in situ ionic liquid induced polymerization and carbonization of the POPs.

Summary The development of highly stable separation agents is recognized as a decisive step toward the successful deployment of energy-efficient and cost-effective separation processes. Here, we report the synthesis and construction of a metal-organic framework (MOF), kag -MOF-1, that has adequate structural and chemical features and affords a stable adsorbent with unique and appropriate adsorption properties for gas processing akin to acid gas removal, dehydration, and benzene-toluene-xylene (BTX) sieving. A combination of X-ray diffraction experiments, adsorption studies, mixed-gas breakthrough adsorption column testing, calorimetric measurements, and molecular simulations corroborated the exceptional separation performance of kag -MOF-1 and its prospective use as a multifunctional adsorbent. The unique adsorption properties of kag -MOF-1, resulting from the contracted pore system with aligned periodic array of exposed functionalities, attest to the prominence of this new generation of ultra-microporous material as a prospective practical adsorbent toward cost-effective and more simplified gas and vapor processing flowcharts for natural gas upgrading and flue gas scrubbing.

In this work, we present the implementation of reticular chemistry and the molecular building block approach to unveil the appropriateness of Rare Earth (RE) based Metal-Organic Frameworks (MOFs) with fcu topology for H2S removal applications. Markedly, RE-fcu-MOFs, having different pore aperture sizes in the range of 4.7–6.0 A and different functionalities, showed excellent properties for the removal of H2S from CO2 and CH4 containing gases such as natural gas, biogas and landfill gas. A series of cyclic mixed gas breakthrough experiments were carried out on three isoreticular fcu-MOFs, containing linkers of different lengths (between 8.4 and 5 A), by using simulated natural gas mixture containing CO2/H2S/CH4 (5%/5%/90%) under different adsorption and regeneration conditions. The fcu-MOF platform has good H2S removal capacity with a high H2S/CO2 selectivity, outperforming benchmark materials like activated carbon and Zeolites in many aspects. The comparison of H2S removal performance with the related structures of the RE-fcu-MOFs provides insightful information to shed light on the relationship between the structural features of the MOF and its associated H2S separation properties. The excellent H2S/CO2 and H2S/CH4 selectivity of these materials offer great prospective for the production of pure H2S, with acceptable levels of CO2for Claus process to produce elemental sulfur.

Highly connected and edge-transitive nets are of prime importance in crystal chemistry and are regarded as ideal blueprints for the rational design and construction of metal–organic frameworks (MOFs). We report the design and synthesis of highly connected MOFs based on reticulation of the sole two edge-transitive nets with a vertex figure as double six-membered-ring (d6R) building unit, namely the (4,12)-coordinated shp net (square and hexagonal-prism) and the (6,12)-coordinated alb net (aluminum diboride, hexagonal-prism and trigonal-prism). Decidedly, the combination of our recently isolated 12-connected (12-c) rare-earth (RE) nonanuclear [RE9(μ3-OH)12(μ3-O)2(O2C–)12] carboxylate-based cluster, points of extension matching the 12 vertices of hexagonal-prism d6R, with 4-connected (4-c) square porphyrinic tetracarboxylate ligand led to the formation of the targeted RE-shp-MOF. This is the first time that RE-MOFs based on 12-c molecular building blocks (MBBs), d6R building units, have been deliberately tar...

A cooperative experimental/modeling strategy was used to unveil the structure/gas separation performance relationship for a series of isostructural metal–organic frameworks (MOFs) with soc-topology (square-octahedral) hosting different extra-framework counter ions (NO3−, Cl− and Br−). In3+-, Fe3+-, Ga3+- and the newly isolated Al(III)-based isostructural soc-MOF were extensively studied and evaluated for the separation-based production of high-quality fuels (i.e., CH4, C3H8 and n-C4H10) and olefins. The structural/chemical fine-tuning of the soc-MOF platform promoted equilibrium-based selectivity toward C2+ (C2H6, C2H4, C3H6 C3H8 and n-C4H10) and conferred the desired chemical stability toward H2S. The noted dual chemical stability and gas/vapor selectivity, which have rarely been reported for equilibrium-based separation agents, are essential for the production of high-purity H2, CH4 and C2+ fractions in high yields. Interestingly, the evaluated soc-MOF analogues exhibited high selectivity for C2H4, C3H6 and n-C4H10. In particular, the Fe, Ga and Al analogues presented relatively enhanced C2+/CH4 adsorption selectivities. Notably, the Ga and Al analogues were found to be technically preferable because their structural integrities and separation performances were maintained upon exposure to H2S, indicating that these materials are highly tolerant to H2S. Therefore, the Ga-soc-MOF was further examined for the selective adsorption of H2S in the presence of CO2- and CH4-containing streams, such as refinery-off gases (ROG) and natural gas (NG). Grand canonical Monte Carlo (GCMC) simulations based on a specific force field describing the interactions between the guest molecules and the Ga sites supported and confirmed the considerably higher affinity of the Ga-soc-MOF for C2+ (as exemplified by n-C4H10) than for CH4. The careful selection of an appropriate metal for the trinuclear inorganic molecular building block (MBB), i.e., a Ga metal center, imbues the soc-MOF platform with the requisite hydrolytic stability, H2S stability, and exceptional gas selectivity for ROG and NG upgrading. Finally, the soc-MOF was deployed as a continuous film on a porous support, and its gas permeation properties as a membrane were evaluated.

The separation of related molecules with similar physical/chemical properties is of prime industrial importance and practically entails a substantial energy penalty, typically necessitating the operation of energy-demanding low temperature fractional distillation techniques. Certainly research efforts, in academia and industry alike, are ongoing with the main aim to develop advanced functional porous materials to be adopted as adsorbents for the effective and energy-efficient separation of various important commodities. Of special interest is the subclass of metal-organic frameworks (MOFs) with pore aperture sizes below 5-7 Å, namely ultra-microporous MOFs, which in contrast to conventional zeolites and activated carbons show great prospects for addressing key challenges in separations pertaining to energy and environmental sustainability, specifically materials for carbon capture and separation of olefin/paraffin, acetylene/ethylene, linear/branched alkanes, xenon/krypton, etc. In this tutorial review we discuss the latest developments in ultra-microporous MOF adsorbents and their use as separating agents via thermodynamics and/or kinetics and molecular sieving. Appreciably, we provide insights into the distinct microscopic mechanisms governing the resultant separation performances, and suggest a plausible correlation between the inherent structural features/topology of MOFs and the associated gas/vapour separation performance.

The development of functional solid-state materials for carbon capture at low carbon dioxide (CO2) concentrations, namely, from confined spaces (0.5%) and in particular from air (400 ppm), is of prime importance with respect to energy and environment sustainability. Herein, we report the deliberate construction of a hydrolytically stable fluorinated metal-organic framework (MOF), NbOFFIVE-1-Ni, with the appropriate pore system (size, shape, and functionality), ideal for the effective and energy-efficient removal of trace carbon dioxide. Markedly, the CO2-selective NbOFFIVE-1-Ni exhibits the highest CO2 gravimetric and volumetric uptake (ca. 1.3 mmol/g and 51.4 cm(3) (STP) cm(-3)) for a physical adsorbent at 400 ppm of CO2 and 298 K. Practically, NbOFFIVE-1-Ni offers the complete CO2 desorption at 328 K under vacuum with an associated moderate energy input of 54 kJ/mol, typical for the full CO2 desorption in conventional physical adsorbents but considerably lower than chemical sorbents. Noticeably, the contracted square-like channels, affording the close proximity of the fluorine centers, permitted the enhancement of the CO2-framework interactions and subsequently the attainment of an unprecedented CO2 selectivity at very low CO2 concentrations. The precise localization of the adsorbed CO2 at the vicinity of the periodically aligned fluorine centers, promoting the selective adsorption of CO2, is evidenced by the single-crystal X-ray diffraction study on NbOFFIVE-1-Ni hosting CO2 molecules. Cyclic CO2/N2 mixed-gas column breakthrough experiments under dry and humid conditions corroborate the excellent CO2 selectivity under practical carbon capture conditions. Pertinently, the notable hydrolytic stability positions NbOFFIVE-1-Ni as the new benchmark adsorbent for direct air capture and CO2 removal from confined spaces.

Separating one organic from another Separating closely related organic molecules is a challenge (see the Perspective by Lin).The separation of acetylene from ethylene is needed in high-purity polymer production. Cui et al. developed a copper-based metal-organic framework with hexafluorosilicate and organic linkers designed to have a high affinity for acetylene. These materials, which capture four acetylene molecules in each pore, successfully separated acetylene from mixtures with ethylene. Propane and propylene are both important feedstock chemicals. Their physical and chemical similarity, however, requires energy-intense processes to separate them. Cadiau et al. designed a fluorinated porous metal-organic framework material that selectively adsorbed propylene, with the complete exclusion of propane. Science , this issue pp. 141 and 137 ; see also p. 121

Metal–organic frameworks (MOFs) are an important class of porous materials with numerous potential applications. Molecular level understanding of various processes involving MOFs is very important in order to design porous materials with improved properties. Here we describe the elucidation by means of single-crystal X-ray diffraction (SCD) of three different phases of Zn2(bdc)2(bpy) at different pressures of CO2. Moreover, this is a rare example where new space is created in the structure under gas pressure – space that was not previously occupied by guest molecules in any of the related structures. In addition to in situ SCD and sorption analysis, pressure-gradient differential scanning calorimetry (PG-DSC) provides very useful information about the system. This study represents the first instance where PG-DSC has been used to study the sorption behavior of a flexible porous framework.

We unveil a unique kinetic driven separation material for selectively removing linear paraffins from iso-paraffins via a molecular sieving mechanism. Subsequent carbonization and thermal treatment of CD-MOF-2, the cyclodextrin metal-organic framework, afforded a carbon molecular sieve with a uniform and reduced pore size of ca. 5.0 Å, and it exhibited highly selective kinetic separation of n-butane and n-pentane from iso-butane and iso-pentane, respectively.

Metal-organic frameworks (MOFs) have emerged as an important and unique class of functional crystalline hybrid porous materials in the past two decades. Due to their modular structures and adjustable pore system, such distinctive materials have exhibited remarkable prospects in key applications pertaining to adsorption such as gas storage, gas and liquid separations, and trace impurity removal. Evidently, gaining a better understanding of the structure-property relationship offers great potential for the enhancement of a given associated MOF property either by structural adjustments via isoreticular chemistry or by the design and construction of new MOF structures via the practice of reticular chemistry. Correspondingly, the application of isoreticular chemistry paves the way for the microfine design and structure regulation of presented MOFs. Explicitly, the microfine tuning is mainly based on known MOF platforms, focusing on the modification and/or functionalization of a precise part of the MOF structure or pore system, thus providing an effective approach to produce richer pore systems with enhanced performances from a limited number of MOF platforms. Here, the latest progress in this field is highlighted by emphasizing the differences and connections between various methods. Finally, the challenges together with prospects are also discussed.

Herein we demonstrate how the combined use of the molecular building block (MBB) approach and reticular chemistry allows the fabrication of a highly stable, ultra-microporous metal–organic framework (MOF) that is an efficient sorbent for the challenging separation of propane/propylene.

Conventional adsorbents, namely zeolites and silica gel, are often used to control humidity by adsorbing water; however, adsorbents capable of the dual functionality of humidification and dehumidification, offering the desired control of the moisture level at room temperature, have yet to be explored. Here we report Y-shp-MOF-5, a hybrid microporous highly connected rare-earth-based metal-organic framework (MOF), with dual functionality for moisture control within the recommended range of relative humidity (45%-65% RH) set by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). Y-shp-MOF-5 exhibits exceptional structural integrity, robustness, and unique humidity-control performance, as confirmed by the large number (thousand) of conducted water vapor adsorption-desorption cycles. The retained structural integrity and the mechanism of water sorption were corroborated using in situ single-crystal X-ray diffraction (SCXRD) studies. The resultant working water uptake of 0.45 g·g

The development of practical solutions for the energy-efficient capture of carbon dioxide is of prime importance and continues to attract intensive research interest. Conceivably, the implementation of adsorption-based processes using different cycling modes, e.g., pressure-swing adsorption or temperature-swing adsorption, offers great prospects to address this challenge. Practically, the successful deployment of practical adsorption-based technologies depends on the development of made-to-order adsorbents expressing mutually two compulsory requisites: i) high selectivity/affinity for CO2 and ii) excellent chemical stability in the presence of impurities. This study presents a new comprehensive experimental protocol apposite for assessing the prospects of a given physical adsorbent for carbon capture under flue gas stream conditions. The protocol permits: i) the baseline performance of commercial adsorbents such as zeolite 13X, activated carbon versus liquid amine scrubbing to be ascertained, and ii) a standardized evaluation of the best reported metal-organic framework (MOF) materials for carbon dioxide capture from flue gas to be undertaken. This extensive study corroborates the exceptional CO2 capture performance of the recently isolated second-generation fluorinated MOF material, NbOFFIVE-1-Ni, concomitant with an impressive chemical stability and a low energy for regeneration. Essentially, the NbOFFIVE-1-Ni adsorbent presents the best compromise by satisfying all the required metrics for efficient CO2 scrubbing.

Drying natural gas efficiently Natural gas must be purified before it can be transported. The preparation process also includes a drying step to remove water. Microporous adsorbents such as zeolites are used for this purpose, but they often need to be heated to temperatures up to 250°C to remove the water so that they can be reused. Cadiau et al. describe a fluorinated metal-organic framework containing nickel metal centers that can remove water from gas streams but that can be regenerated by heating to only 105°C. Science , this issue p. 731