Adsorption of hydrogen and methane on intrinsic and alkali metal cations-doped Zn<Subscript>2</Subscript>(NDC)<Subscript>2</Subscript>(diPyTz) metal–organic framework using GCMC simulations

In this study, the adsorption of hydrogen and methane on the Zn₂(NDC)₂(diPyTz) [(NDC = 2,6-naphthalenedicarboxylate, diPyTz = di-3,6-(4-pyridyl)-1,2,4,5-tetrazine)] metal–organic framework (MOF) and the effect of its doping with alkali metal cations (Li⁺, Na⁺, K⁺) were investigated using Grand Canonical Monte Carlo simulations. The results indicated that the triply catenating Zn₂(NDC)₂(diPyTz), possessing small pores preferentially adsorbed hydrogen. Doping of Zn₂(NDC)₂(diPyTz) with alkali metal cations enhanced the hydrogen adsorption on the MOF. However, this enhancement became weaker as the atomic number of metal cation increased. The simulation results showed that the hydrogen adsorption on the Li⁺-doped Zn₂(NDC)₂(diPyTz) was almost 2.35 times greater than that of the corresponding undoped MOF at low pressure and room temperature. This suggests that the doping of MOFs with alkali metal cations especially lithium is a desired strategy for hydrogen storage. Furthermore, the results revealed that the adsorption of hydrogen on the Zn₂(NDC)₂(diPyTz) was higher than that of methane at room temperature.     

Water‐stable Adenine‐based MOFs with Polar Pores for Selective CO2 Capture

Here, we report two novel water‐stable amine‐functionalized MOFs, namely IISERP‐MOF26 ([NH₂(CH₃)₂][Cu₂O(Ad)(BDC)]?(H₂O)₂(DMA), 1 ) and IISERP‐MOF27 ([NH₂(CH₃)₂]_1/2[Zn₄O(Ad)₃(BDC)₂]?(H₂O)₂(DMF)_1/2, 2 ), which show selective CO₂ capture capabilities. They are made by combining inexpensive and readily available terephthalic acid and N‐rich adenine with Cu and Zn, respectively. They possess 1D channels decorated by the free amine group from the adenine and the polarizing oxygen atoms from the terephthalate units. Even more, there are dimethyl ammonium (DMA⁺) cations in the pore rendering an electrostatic environment within the channels. The activated Cu‐ and Zn‐MOFs physisorb about 2.7 and 2.2 mmol g^?1 of CO₂, respectively, with high CO₂/N₂ and moderate CO₂/CH₄ selectivity. The calculated heat of adsorption (HOA=21–23 kJ mol^?1) for the CO₂ in both MOFs suggest optimal physical interactions which corroborate well with their facile on‐off cycling of CO₂. Notably, both MOFs retain their crystallinity and porosity even after soaking in water for 24 hours as well as upon exposure to steam over 24 hours. The exceptional thermal and chemical stability, favorable CO₂ uptakes and selectivity and low HOA make these MOFs promising sorbents for selective CO₂ capture applications. However, the MOF′s low heat of adsorption despite having a highly CO₂‐loving groups lined walls is quite intriguing.     

MIL‐53(Al) as a Versatile Platform for Ionic‐Liquid/MOF Composites to Enhance CO2 Selectivity over CH4 and N2

Five different imidazolium‐based ionic liquids (ILs) were incorporated into a metal–organic framework (MOF), MIL‐53(Al), to investigate the effect of IL incorporation on the CO₂ separation performance of MIL‐53(Al). CO₂, CH₄, and N₂ adsorption isotherms of the IL/MIL‐53(Al) composites and pristine MIL‐53(Al) were measured to evaluate the effect of the ILs on the CO₂/CH₄ and CO₂/N₂ selectivities of the MOF. Of the composite materials that were tested, [BMIM][PF₆]/MIL‐53(Al) exhibited the largest increase in CO₂/CH₄ selectivity, 2.8‐times higher than that of pristine MIL‐53(Al), whilst [BMIM][MeSO₄]/MIL‐53(Al) exhibited the largest increase in CO₂/N₂ selectivity, 3.3‐times higher than that of pristine MIL‐53(Al). A comparison of the CO₂ separation potentials of the IL/MOF composites showed that the [BMIM][BF₄]‐ and [BMIM][PF₆]‐incorporated MIL‐53(Al) composites both showed enhanced CO₂/N₂ and CO₂/CH₄ selectivities at pressures of 1–5 bar compared to composites of CuBTC and ZIF‐8 with the same ILs. These results demonstrate that MIL‐53(Al) is a versatile platform for IL/MOF composites and could help to guide the rational design of new composites for target gas‐separation applications.     

Post‐Synthetic Reversible Incorporation of Organic Linkers into Porous Metal–Organic Frameworks through Single‐Crystal‐to‐Single‐Crystal Transformations and Modification of Gas‐Sorption Properties

The porous metal–organic framework (MOF) {[Zn₂(TCPBDA)(H₂O)₂]?30 DMF?6 H₂O}_n ( SNU‐30 ; DMF=N,N‐dimethylformamide) has been prepared by the solvothermal reaction of N,N,N′,N′‐tetrakis(4‐carboxyphenyl)biphenyl‐4,4′‐diamine (H₄TCPBDA) and Zn(NO₃)₂?6 H₂O in DMF/tBuOH. The post‐synthetic modification of SNU‐30 by the insertion of 3,6‐di(4‐pyridyl)‐1,2,4,5‐tetrazine (bpta) affords single‐crystalline {[Zn₂(TCPBDA)(bpta)]?23 DMF?4 H₂O}_n ( SNU‐31 SC ), in which channels are divided by the bpta linkers. Interestingly, unlike its pristine form, the bridging bpta ligand in the MOF is bent due to steric constraints. SNU‐31 can be also prepared through a one‐pot solvothermal synthesis from Zn^II, TCPBDA^4?, and bpta. The bpta linker can be liberated from this MOF by immersion in N,N‐diethylformamide (DEF) to afford the single‐crystalline SNU‐30 SC , which is structurally similar to SNU‐30 . This phenomenon of reversible insertion and removal of the bridging ligand while preserving the single crystallinity is unprecedented in MOFs. Desolvated solid SNU‐30′ adsorbs N₂, O₂, H₂, CO₂, and CH₄ gases, whereas desolvated SNU‐31′ exhibits selective adsorption of CO₂ over N₂, O₂, H₂, and CH₄, thus demonstrating that the gas adsorption properties of MOF can be modified by post‐synthetic insertion/removal of a bridging ligand.     

A Cationic MOF with High Uptake and Selectivity for CO2 due to Multiple CO2‐Philic Sites

The reaction of N‐rich pyrazinyl triazolyl carboxyl ligand 3‐(4‐carboxylbenzene)‐5‐(2‐pyrazinyl)‐1H‐1,2,4‐triazole (H₂cbptz) with MnCl₂ afforded 3D cationic metal–organic framework (MOF) [Mn₂(Hcbptz)₂(Cl)(H₂O)]Cl ? DMF ? 0.5 CH₃CN ( 1 ), which has an unusual (3,4)‐connected 3,4T1 topology and 1D channels composed of cavities. MOF 1 has a very polar framework that contains exposed metal sites, uncoordinated N atoms, narrow channels, and Cl^? basic sites, which lead to not only high CO₂ uptake, but also remarkably selective adsorption of CO₂ over N₂ and CH₄ at 298–333 K. The multiple CO₂‐philic sites were identified by grand canonical Monte Carlo simulations. Moreover, 1 shows excellent stability in natural air environment. These advantages make 1 a very promising candidate in post‐combustion CO₂ capture, natural‐gas upgrading, and landfill gas‐purification processes.     

Microwave‐Assisted Hydrothermal Synthesis of [Al(OH)(1,4‐NDC)] Membranes with Superior Separation Performances

In this study, we report a facile ligand‐assisted in situ hydrothermal approach for preparation of compact [Al(OH)(1,4‐NDC)] (1,4‐NDC=1,4‐naphthalenedicarboxylate) MOF membranes on porous γ‐Al₂O₃ substrates, which also served as the Al³⁺ source of MOF membranes. Simultaneously, it was observed that the heating mode exerted significant influence on the final microstructure and separation performance of [Al(OH)(1,4‐NDC)] membranes. Compared with the conventional hydrothermal method, the employment of microwave heating led to the formation of [Al(OH)(1,4‐NDC)] membranes composed of closely packed nanorods with superior H₂/CH₄ selectivity.     

Co3(HCOO)6 microporous metal-organic framework membrane for separation of CO2/CH4 mixtures

Continuous metal–organic framework‐type Co₃(HCOO)₆ intergrown films with a one‐dimensional zigzag channel system and pore aperture of 5.5 Å are prepared by secondary growth on preseeded macroporous glass‐frit disks and silicon wafers. The adsorption behavior of CO₂ or CH₄ single gases on the Co₃(HCOO)₆ membrane is investigated by in situ IR spectroscopy. It is shown that the isosteric heats of adsorption for CO₂ (17.7 kJ mol^?1) and CH₄ (14.4 kJ mol^?1) do not vary with increasing amount of adsorbed gases. The higher value of isosteric heat for CO₂ is an indication of the stronger interaction between the CO₂ and the Co₃(HCOO)₆ membrane. The Co₃(HCOO)₆ membrane is studied by binary gas permeation of CO₂ and CH₄ at different temperatures (0, 25, and 60 °C). The membrane has CO₂/CH₄ selectivity with a separation factor higher than 10, which is due to the unique structure and molecular sieving effect. Upon increasing the temperature from 0 to 60 °C, the preferred permeance of CO₂ over CH₄ is increased from 1.70×10^?6 to 2.09×10^?6 mol m^?2 s^?1 Pa^?1, while the separation factor for CO₂/CH₄ shows a corresponding decrease from 15.95 to 10.37. The effective pore size of the Co₃(HCOO)₆ material combined with the pore shape do not allow the two molecules to pass simultaneously, and once the CO₂ molecules are diffused in the micropores, the CH₄ is blocked. The supported Co₃(HCOO)₆ membrane retains high mechanical stability after a number of thermal cycles.     

Ligand and Metal Effects on the Stability and Adsorption Properties of an Isoreticular Series of MOFs Based on T‐Shaped Ligands and Paddle‐Wheel Secondary Building Units

The synthesis of stable porous materials with appropriate pore size and shape for desired applications remains challenging. In this work a combined experimental/computational approach has been undertaken to tune the stability under various conditions and the adsorption behavior of a series of MOFs by subtle control of both the nature of the metal center (Co²⁺, Cu²⁺, and Zn²⁺) and the pore surface by the functionalization of the organic linkers with amido and N‐oxide groups. In this context, six isoreticular MOFs based on T‐shaped ligands and paddle‐wheel units with ScD_0.33 topology have been synthesized. Their stabilities have been systematically investigated along with their ability to adsorb a wide range of gases (N₂, CO₂, CH₄, CO, H_2, light hydrocarbons (C₁–C₄)) and vapors (alcohols and water). This study has revealed that the MOF frameworks based on Cu²⁺ are more stable than their Co²⁺ and Zn²⁺ analogues, and that the N‐oxide ligand endows the MOFs with a higher affinity for CO₂ leading to excellent selectivity for this gas over other species.     

Analysis of High and Selective Uptake of CO2 in an Oxamide‐Containing {Cu2(OOCR)4}‐Based Metal–Organic Framework

The porous framework [Cu₂(H₂O)₂L] ? 4 H₂O ? 2 DMA (H₄L=oxalylbis(azanediyl)diisophthalic acid; DMA=N,N‐dimethylacetamide), denoted NOTT‐125, is formed by connection of {Cu₂(RCOO)₄} paddlewheels with the isophthalate linkers in L^4?. A single crystal structure determination reveals that NOTT‐125 crystallises in monoclinic unit cell with a=27.9161(6), b=18.6627(4) and c=32.3643(8) Å, β=112.655(3)°, space group P2₁/c. The structure of this material shows fof topology, which can be viewed as the packing of two types of cages (cage A and cage B) in three‐dimensional space. Cage A is constructed from twelve {Cu₂(OOCR)₄} paddlewheels and six linkers to form an ellipsoid‐shaped cavity approximately 24.0 Å along its long axis and 9.6 Å across its central diameter. Cage B consists of six {Cu₂(OOCR)₄} units and twelve linkers and has a spherical diameter of 12.7 Å taking into account the van der Waals radii of the atoms. NOTT‐125 incorporates oxamide functionality within the pore walls, and this, combined with high porosity in desolvated NOTT‐125a, is responsible for excellent CO₂ uptake (40.1 wt % at 273 K and 1 bar) and selectivity for CO₂ over CH₄ or N₂. Grand canonical Monte Carlo (GCMC) simulations show excellent agreement with the experimental gas isotherm data, and a computational study of the specific interactions and binding energies of both CO₂ and CH₄ with the linkers in NOTT‐125 reveals a set of strong interactions between CO₂ and the oxamide motif that are not possible with a single amide.     

Enhanced CO2 Adsorption Affinity in a NbO‐type MOF Constructed from a Low‐Cost Diisophthalate Ligand with a Piperazine‐Ring Bridge

A metal–organic framework (NPC‐6) with an NbO topology based on a piperazine ring‐bridged diisophthalate ligand was synthesized and characterized. The incorporated piperazine group leads to an enhanced adsorption affinity for CO₂ in NPC‐6, in which the CO₂ uptake is 4.83 mmol g^?1 at 293 K and 1 bar, ranking among the top values of CO₂ uptake on MOF materials. At 0.15 bar and 293 K, the NPC‐6 adsorbs 1.07 mmol g^?1 of CO₂, which is about 55.1 % higher than that of the analogue MOF NOTT‐101 under the same conditions. The enhanced CO₂ uptake combined with comparable uptakes for CH₄ and N₂ leads to much higher selectivities for CO₂/CH₄ and CO₂/N₂ gas mixtures on NPC‐6 than on NOTT‐101. Furthermore, an N‐alkylation is used in the synthesis of the PDIA ligand, leading to a much lower cost compared with that in the synthesis of ligands in the NOTT series, as the former does not require a palladium‐based catalyst and borate esters. Thus, we conclude that NPC‐6 is a promising candidate for CO₂ capture applications.     

[Li(THF)][Zn3(CH2CN)3(LiBr)(NPMe3)4] — ein funktionalisierter Phosphaniminato‐Komplex von Zink mit supramolekularer Struktur

[Li(THF)][Zn₃(CH₂CN)₃(LiBr)(NPMe₃)₄] — a functionalized Phosphoraneiminato Complex of Zinc with Supramolecular Structure [Li(THF)][Zn₃(CH₂CN)₃(LiBr)(NPMe₃)₄] ( 1 ) has been prepared from the heterocubane [ZnBr(NPMe₃)]₄ and LiCH₂CN in tetrahydrofuran suspension to give colourless crystals which were characterized by IR‐spectroscopy and by a crystal structure analysis. 1 crystallizes in the orthorhombic space group Pnam with four units per unit cell. Lattice dimensions at 203 K: a = 2156.9(10), b = 1546.9(14), c = 1226.2(4) pm, R₁ = 0.0756. The structure consists of the anionic heterocubane [Zn₃(CH₂CN)₃(LiBr)(NPMe₃)₄]^—, the eight skeleton atoms of which are the three zinc atoms and the lithium atom as well as the four nitrogen atoms of the phosphoraneiminato groups. The charge of this anionic cube is compensated by a Li⁺‐ion to which is coordinated a THF molecule, as well as three cyanomethyl‐nitrogen atoms of three different cubes. This results in the formation of a three‐dimensional supramolecular structure.     

Theoretical simulation of CO2 capture in organic cage impregnated with polyoxometalates

To explore the adsorption and separation properties of CO₂ in a novel material consisting of a series of polyoxometalates (POMs) impregnated within supramolecular porous catenane (shorted as SPC), grand canonical Monte Carlo (GCMC) simulations and ab initio calculations were used. GCMC simulations showed this impregnation can enhance CO₂/CH₄ (or CO₂/N₂) selectivity almost 30 times compared to the bare SPC due to the strong interaction of CO₂ with the nPOMs@SPC structures. And, the loading of CO₂ inhibits the adsorption of CH₄ (or N₂) as CO₂ occupying the preferred adsorption sites. Furthermore, the effect of number, mass, and volume of POMs inserted in SPC on CO₂/CH₄ (or CO₂/N₂) selectivity over large pressure range was investigated in detail. Additionally, the accurate ab initio calculations further confirmed our GCMC simulations. As a result, the proposed nPOMs@SPC structures are promising candidates for CO₂/N₂ and CO₂/CH₄ separations. © 2017 Wiley Periodicals, Inc.     

Highly efficient CO2 capture with a metal–organic framework‐derived porous carbon impregnated with polyethyleneimine

Global warming is considered as one of the great challenges of the twenty‐first century. Application of CO₂ capture and storage technologies to flue gas is considered to be a useful method of lessening global warning. Highly porous carbon has played an important role in tackling energy and environmental problems. We attempted to synthesize a highly porous carbon adsorbent by carbonizing a highly crystalline metal–organic framework (MOF) without any carbon precursors and focused on the adsorption of CO₂ and CH₄ gases and CO₂/CH₄ selectivity at 298, 323 and 348 K using a volumetric apparatus. The MOF‐derived porous carbon (MDC) was prepared by direct carbonization of MOF‐199 as a template at 900 °C under nitrogen atmosphere. Amino‐impregnated MDC samples exhibited enhanced adsorption capacities by a combination of physical and chemical adsorption. Polyethyleneimine (PEI) was selected as the amine source, which was found to greatly enhance CO₂ capture when supported on the porous carbon. Novel PEI‐impregnated MDC nanocomposites were synthesized by wetness impregnation and then characterized using various methods.     

Tuning CO2 Uptake and Reversible Iodine Adsorption in Two Isoreticular MOFs through Ligand Functionalization

The synthesis and characterization of two isoreticular metal–organic frameworks (MOFs), {[Cd(bdc)(4‐bpmh)]}_n?2 n(H₂O) ( 1 ) and {[Cd(2‐NH₂bdc)(4‐bpmh)]}_n?2 n(H₂O) ( 2 ) [bdc=benzene dicarboxylic acid; 2‐NH₂bdc=2‐amino benzene dicarboxylic acid; 4‐bpmh=N,N‐bis‐pyridin‐4‐ylmethylene‐hydrazine], are reported. Both compounds possess similar two‐fold interpenetrated 3D frameworks bridged by dicarboxylates and a 4‐bpmh linker. The 2D Cd‐dicarboxylate layers are extended along the a‐axis to form distorted square grids which are further pillared by 4‐bpmh linkers to result in a 3D pillared‐bilayer interpenetrated framework. Gas adsorption studies demonstrate that the amino‐functionalized MOF 2 shows high selectivity for CO₂ (8.4 wt % 273 K and 7.0 wt % 298 K) over CH₄, and the uptake amounts are almost double that of non‐functional MOF 1 . Iodine (I₂) adsorption studies reveal that amino‐functionalized MOF 2 exhibits a faster I₂ adsorption rate and controlled delivery of I₂ over the non‐functionalized homolog 1 .     

From Molecules to Materials: Computational Design of N‐Containing Porous Aromatic Frameworks for CO2 Capture

Porous aromatic frameworks (PAFs) are novel materials with diamond topology. With the aim of enhancing their CO₂ capture and storage capacity and investigating the effect of nitrogen and/or ‐COOH decorations on CO₂ adsorption in PAFs, a series of N‐containing PAFs were designed based on ab initio results. The interaction energies (E_int) between CO₂ and each six‐membered ring were calculated at the B2PLYP‐D2/def2‐TZVPP level, then the six‐membered rings with high CO₂‐binding affinity were selected and used in the PAFs. To explore the performance of the designed PAFs, the CO₂ uptake, selectivity of CO₂ over CH₄, H₂, and N₂, and the E_int value of CO₂ in PAFs were investigated by using grand canonical Monte Carlo (GCMC) simulations and ab initio calculations. This work shows that pyridine with one nitrogen atom can provide a strong physisorption site for CO₂, whereas more nitrogen atoms in heterocycles will reduce the interaction, especially at relatively low pressure. PAFs with ?COOH groups show high CO₂ capacity. Our work provides an efficient way to understand the adsorption mechanism and a supplemental approach to experimental work.     

Dynamic Entangled Porous Framework for Hydrocarbon (C2–C3) Storage,CO2 Capture,and Separation

Storage and separation of small (C1–C3) hydrocarbons are of great significance as these are alternative energy resources and also can be used as raw materials for many industrially important materials. Selective capture of greenhouse gas, CO₂ from CH₄ is important to improve the quality of natural gas. Among the available porous materials, MOFs with permanent porosity are the most suitable to serve these purposes. Herein, a two‐fold entangled dynamic framework {[Zn₂(bdc)₂(bpNDI)]?4DMF}_n with pore surface carved with polar functional groups and aromatic π clouds is exploited for selective capture of CO₂, C2, and C3 hydrocarbons at ambient condition. The framework shows stepwise CO₂ and C₂H₂ uptake at 195 K but type I profiles are observed at 298 K. The IAST selectivity of CO₂ over CH₄ is the highest (598 at 298 K) among the MOFs without open metal sites reported till date. It also shows high selectivity for C₂H₂, C₂H₄, C₂H₆, and C₃H₈ over CH₄ at 298 K. DFT calculations reveal that aromatic π surface and the polar imide (RNC=O) functional groups are the primary adsorption sites for adsorption. Furthermore, breakthrough column experiments showed CO₂/CH₄ C₂H₆/CH₄ and CO₂/N₂ separation capability at ambient condition.     

Structural analysis of interpenetrated methyl‐modified MOF‐5 and its gas‐adsorption properties

The first example of an interpenetrated methyl‐modified MOF‐5 with the formula Zn₄O(DMBDC)₃(DMF)₂, where DMBDC^2? is 2,5‐dimethylbenzene‐1,4‐dicarboxylate and DMF is N,N‐dimethylformamide (henceforth denoted as Me₂MOF‐5‐int ), namely, poly[tris(μ₄‐2,5‐dimethylbenzene‐1,4‐dicarboxylato)bis(N,N‐dimethylformamide)‐μ₄‐oxido‐tetrazinc(II)], [Zn₄(C₁₀H₈O₄)₃O(C₃H₇NO)₂]_n, has been obtained from a solvothermal synthesis of 2,5‐dimethylbenzene‐1,4‐dicarboxylic acid and Zn(NO₃)₂·6H₂O in DMF. A systematic study revealed that the choice of solvent is of critical importance for the synthesis of phase‐pure Me₂MOF‐5‐int , which was thoroughly characterized by single‐crystal and powder X‐ray diffraction (PXRD), as well as by gas‐adsorption analyses. The Brunauer–Emmett–Teller surface area of Me₂MOF‐5‐int (660 m² g^?1), determined by N₂ adsorption, is much lower than that of nonpenetrated Me₂MOF‐5 (2420 m² g^?1). However, Me₂MOF‐5‐int displays an H₂ uptake capacity of 1.26 wt% at 77 K and 1.0 bar, which is comparable to that of non‐interpenetrated Me₂MOF‐5 (1.51 wt%).     

Adsorption equilibria of CO<Subscript>2</Subscript> and CH<Subscript>4</Subscript> in cation-exchanged zeolites 13X

Ion-exchange with different cations (Na⁺, NH₄ ⁺, Li⁺, Ba²⁺ and Fe³⁺) was performed in binderless 13X zeolite pellets. Original and cation-exchanged samples were characterized by thermogravimetric analysis coupled with mass spectrometry (inert atmosphere), X-ray powder diffraction and N₂ adsorption/desorption isotherms at 77 K. Despite the presence of other cations than Na (as revealed in TG-MS), crystalline structure and textural properties were not significantly altered upon ion-exchange. Single component equilibrium adsorption isotherms of carbon dioxide (CO₂) and methane (CH₄) were measured for all samples up to 10 bar at 298 and 348 K using a magnetic suspension balance. All of these isotherms are type Ia and maximum adsorption capacities decrease in the order Li > Na > NH₄–Ba > Fe for CO₂ and NH₄–Na > Li > Ba for CH₄. In addition to that, equilibrium adsorption data were measured for CO₂/CH₄ mixtures for representative compositions of biogas (50 % each gas, in vol.) and natural gas (30 %/70 %, in vol.) in order to assess CO₂ selectivity in such scenarios. The application of the Extended Sips Model for samples BaX and NaX led to an overall better agreement with experimental data of binary gas adsorption as compared to the Extended Langmuir Model. Fresh sample LiX show promise to be a better adsorption than NaX for pressure swing separation (CO₂/CH₄), due to its higher working capacity, selectivity and lower adsorption enthalpy. Nevertheless, cation stability for both this samples and NH₄X should be further investigated.     

In situ Synchrotron IR Microspectroscopy of CO2 Adsorption on Single Crystals of the Functionalized MOF Sc2(BDC‐NH2)3

Synchrotron radiation (SR) IR microspectroscopy has enabled determination of the thermodynamics, kinetics, and molecular orientation of CO₂ adsorbed in single microcrystals of a functionalized metal–organic framework (MOF) under conditions relevant to carbon capture from flue gases. Single crystals of the small‐pore MOF, Sc₂(BDC‐NH₂)₃, (BDC‐NH₂=2‐amino‐1,4‐benzenedicarboxylate), with well‐defined crystal form have been investigated during CO₂ uptake at partial pressures of 0.025‐0.2 bar at 298–373 K. The enthalpy and diffusivity of adsorption determined from individual single crystals are consistent with values obtained from measurements on bulk samples. The brilliant SR IR source permits rapid collection of polarized spectra. Strong variations in absorbance of the symmetric stretch of the NH₂ groups of the MOF and the asymmetric stretch of the adsorbed CO₂ at different orientations of the crystals relative to the polarized IR light show that CO₂ molecules align along channels in the MOF.     

A New Microporous Metal‐Organic Framework for Highly Selective C2H2/CH4 and C2H2/CO2 Separation at Room Temperature

We have successfully designed and synthesized a new tetracarboxylic linker, which constructed its first three‐dimensional microporous metal‐organic framework (MOF ), [Cu₂(DDPD )(H₂O )₂]•Gx ( ZJU ‐13 , H₄DDPD =5,5'‐(2,6‐dihydroxynaphthalene‐1,5‐diyl)diisophthalic acid, ZJU =Zhejiang University, G = guest molecules) via solvothermal reaction. Due to open Cu²⁺ sites and optimized pore size, the activated ZJU ‐13a displays high separation selectivity for C₂H₂ /CH₄ of 74 and C₂H₂ /CO₂ of 12.5 at low pressure by using Ideal Adsorbed Solution Theory (IAST ) simulation at room temperature.