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Herein, a post‐synthetic modification strategy is used to covalently graft polyamines, including ethylenediamine (ED), diethylenetriamine (DETA), tris(2‐aminoethyl)amine (TAEA), and polyethyleneimine (PEI) to the amino‐ligand inside of a Cr‐MOF, NH2‐Cr‐BDC, for post‐combustion carbon capture applications. X‐ray absorption spectroscopy (XAS), X‐ray photoelectron spectroscopy (XPS), and ion chromatography (IC) reveal that ≈45% of the MOF ligands are grafted with polyamines. Next, assessment of CO2 uptake, CO2/N2 selectivity, isosteric heats of CO2 adsorption, separation performance during humid CO2/N2 (15/85) breakthrough experiments, and cyclability, reveals an enhanced performance for the polyamine‐containing composites and the following performance trend: NH2‐Cr‐BDC

The complexes [Co(NH3)6][Ir(C2O4)3] and [Ir(NH3)6][Co(C2O4)3].H2O have previously been synthesized and their thermal properties studied. The [Ir(NH3)6][Ir(C2O4)3] and [Co(NH3)6][Co(C2O4)3].3H2O complexes considered here are the end members in a series of possible isostructural solid solutions based on the complex salts in the Co-Ir system. Their crystal structures and thermal properties are described in detail, including temperature-dependent in situ X-ray diffraction. During the thermolysis of these compounds, layered metal nanoparticles are formed. Close attention is paid to the details of the [Co(NH3)6][Ir(C2O4)3] synthesis. It has been shown that the formation of this complex salt is temperature dependent; upon heating, a new phase of the K3[Co(NH3)6][Ir(C2O4)3]2.6H2O salt is formed, which incorporates the initial iridium compound into the crystal structure of the double complex salt. The target [Co(NH3)6][Ir(C2O4)3] product is obtained if the synthesis is carried out at room temperature. [ABSTRACT FROM AUTHOR]

The complexes [Co(NH3)6][Ir(C2O4)3] and [Ir(NH3)6][Co(C2O4)3]·H2O have previously been synthesized and their thermal properties studied. The [Ir(NH3)6][Ir(C2O4)3] and [Co(NH3)6][Co(C2O4)3]·3H2O complexes considered here are the end members in a series of possible isostructural solid solutions based on the complex salts in the Co–Ir system. Their crystal structures and thermal properties are described in detail, including temperature‐dependent in situ X‐ray diffraction. During the thermolysis of these compounds, layered metal nanoparticles are formed. Close attention is paid to the details of the [Co(NH3)6][Ir(C2O4)3] synthesis. It has been shown that the formation of this complex salt is temperature dependent; upon heating, a new phase of the K3[Co(NH3)6][Ir(C2O4)3]2·6H2O salt is formed, which incorporates the initial iridium compound into the crystal structure of the double complex salt. The target [Co(NH3)6][Ir(C2O4)3] product is obtained if the synthesis is carried out at room temperature.This work contains new data on the temperature‐dependent synthesis of iridium and cobalt complex salts, as well as a detailed study of their thermal properties. [ABSTRACT FROM AUTHOR]

Cu-TDPAT (H6TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine), a stable nanoporous metal-organic framework with rht topology, has sparked broad interest as an adsorbent for several chemical separation processes. In this work, in situ synchrotron diffraction experiments followed by sequential LeBail refinements reveal that Cu-TDPAT shows unusually large anisotropic negative thermal expansion (NTE). The PASCal crystallography tool, used to analyze the magnitude of the NTE, reveals an average volumetric thermal expansion coefficient αv = −20.3 MK−1. This value is significantly higher than the one reported for Cu-BTC (also known as HKUST-1), which contains the same Cu-paddlewheel building unit, αv ≈ −12 MK−1. In situ synchrotron single crystal X-ray diffraction and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were employed to shed light on the NTE mechanism. Using these two methods, we were able to elucidate the three main structural motions that are responsible for the NTE effect. The more pronounced NTE behavior of Cu-TDPAT is attributed to the lower symmetry combined with the more complex ligand structure when compared to Cu-BTC. The knowledge obtained in this work is important for understanding the behavior of the adsorbent under transient variable temperature conditions in fixed adsorption beds. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are porous, tunable crystalline materials that are attracting widespread scientific attention for their potential use in post-combustion CO2 capture. In this work, we report the synthesis of a new ligand, 1,3-bis(4-carboxyphenyl)-4,5-dihydro-1H-imidazol-3-ium tetrafluoroborate, H2Sp5-BF4, that is subsequently used for the construction of a novel MOF, Cu-Sp5-EtOH. This highly crystalline material has a charged framework that is expected to give rise to high CO2/N2 selectivity. However, the pores of the parent structure could not be accessed due to the presence of strongly coordinated ethanol molecules. After solvent exchange with methanol and subsequently heating Cu-Sp5-MeOH under vacuum, we are able to liberate the solvent providing other small molecules like CO2 access to the inside of the now porous structure, Cu-Sp5. The combination of open metal sites and framework charge leads to an exceptionally high CO2/N2 selectivity, as determined by Ideal Adsorbed Solution Theory (IAST) calculations performed on single-component adsorption isotherms. The CO2/N2 selectivity of Cu-Sp5 reaches a value of over 200 at pressures typically found in post-combustion flue gas (0.15 bar CO2/0.85 bar N2), a value that is among the highest reported to date. [ABSTRACT FROM AUTHOR]

The complexes [Co(NH3)6][Ir(C2O4)3] and [Ir(NH3)6][Co(C2O4)3].H2O have previously been synthesized and their thermal properties studied. The [Ir(NH3)6][Ir(C2O4)3] and [Co(NH3)6][Co(C2O4)3].3H2O complexes considered here are the end members in a series of possible isostructural solid solutions based on the complex salts in the Co-Ir system. Their crystal structures and thermal properties are described in detail, including temperature-dependent in situ X-ray diffraction. During the thermolysis of these compounds, layered metal nanoparticles are formed. Close attention is paid to the details of the [Co(NH3)6][Ir(C2O4)3] synthesis. It has been shown that the formation of this complex salt is temperature dependent; upon heating, a new phase of the K3[Co(NH3)6][Ir(C2O4)3]2.6H2O salt is formed, which incorporates the initial iridium compound into the crystal structure of the double complex salt. The target [Co(NH3)6][Ir(C2O4)3] product is obtained if the synthesis is carried out at room temperature. [ABSTRACT FROM AUTHOR]

The complexes [Co(NH3)6][Ir(C2O4)3] and [Ir(NH3)6][Co(C2O4)3]·H2O have previously been synthesized and their thermal properties studied. The [Ir(NH3)6][Ir(C2O4)3] and [Co(NH3)6][Co(C2O4)3]·3H2O complexes considered here are the end members in a series of possible isostructural solid solutions based on the complex salts in the Co–Ir system. Their crystal structures and thermal properties are described in detail, including temperature‐dependent in situ X‐ray diffraction. During the thermolysis of these compounds, layered metal nanoparticles are formed. Close attention is paid to the details of the [Co(NH3)6][Ir(C2O4)3] synthesis. It has been shown that the formation of this complex salt is temperature dependent; upon heating, a new phase of the K3[Co(NH3)6][Ir(C2O4)3]2·6H2O salt is formed, which incorporates the initial iridium compound into the crystal structure of the double complex salt. The target [Co(NH3)6][Ir(C2O4)3] product is obtained if the synthesis is carried out at room temperature.This work contains new data on the temperature‐dependent synthesis of iridium and cobalt complex salts, as well as a detailed study of their thermal properties. [ABSTRACT FROM AUTHOR]

The complexes [Co(NH 3 ) 6 ][Ir(C 2 O 4 ) 3 ] and [Ir(NH 3 ) 6 ][Co(C 2 O 4 ) 3 ]·H 2 O have previously been synthesized and their thermal properties studied. The [Ir(NH 3 ) 6 ][Ir(C 2 O 4 ) 3 ] and [Co(NH 3 ) 6 ][Co(C 2 O 4 ) 3 ]·3H 2 O complexes considered here are the end members in a series of possible isostructural solid solutions based on the complex salts in the Co-Ir system. Their crystal structures and thermal properties are described in detail, including temperature-dependent in situ X-ray diffraction. During the thermolysis of these compounds, layered metal nanoparticles are formed. Close attention is paid to the details of the [Co(NH 3 ) 6 ][Ir(C 2 O 4 ) 3 ] synthesis. It has been shown that the formation of this complex salt is temperature dependent; upon heating, a new phase of the K 3 [Co(NH 3 ) 6 ][Ir(C 2 O 4 ) 3 ] 2 ·6H 2 O salt is formed, which incorporates the initial iridium compound into the crystal structure of the double complex salt. The target [Co(NH 3 ) 6 ][Ir(C 2 O 4 ) 3 ] product is obtained if the synthesis is carried out at room temperature.

Functionalizing metal-organic frameworks (MOFs) with amines is a commonly used strategy to enhance their performance in CO 2 capture applications. As such, in this work, a two-step strategy to covalently functionalize NH 2 -containing MOFs with short chain polyamines was developed. In the first step, the parent MOF, Zn 4 O(NH 2 -BDC) 3 , was exposed to bromoacetyl bromide (BrAcBr), which readily reacts with pendant -NH 2 groups on the 2-amino-1,4-benzenedicarboxylate (NH 2 -BDC 2- ) ligand. 1 H NMR of the digested MOF sample revealed that as much as 90% of the MOF ligands could be functionalized in the first step. Next, the MOF samples 60% of the ligands functionalized with acetyl bromide, Zn 4 O(NH 2 -BDC) 1.2 (BrAcNH-BDC) 1.8 , was exposed to several short chain amines including ethylenediamine (ED), diethylenetriamine (DETA), and tris(2-aminoethyl)amine (TAEA). Subsequent digested 1 H NMR analysis indicated that a total of 30%, 28%, and 19% of the MOF ligands were successfully grafted to ED, DETA, and TAEA, respectively. Next, the CO 2 adsorption properties of the amine grafted MOFs were studied. The best performing material, TAEA-appended-Zn 4 O(NH 2 -BDC) 1.2 (BrAcNH-BDC) 1.8 , exhibits a zero-coverage isosteric heat of CO 2 adsorption of -62.5 kJ/mol, a value that is considerably higher than the one observed for the parent framework, -21 kJ/mol. Although the boosted CO 2 affinity only leads to a slight increase in the CO 2 adsorption capacity in the low-pressure regime (0.15 bar), which is of interest in postcombustion carbon dioxide capture, the CO 2 /N 2 (15/85) selectivity at 313 K is 143, a value that is ∼35 times higher than the one observed for Zn 4 O(NH 2 -BDC) 3 , 4.1. Such enhancements are attributed to accessible primary amines, which were grafted to the MOF ligand. This hypothesis was further supported via in situ DRIFTS measurements of TAEA-Ac-Zn 4 O(NH 2 -BDC) 1.2 (BrAcNH-BDC) 1.8 after exposure to CO 2 , which revealed the chemisorption of CO 2 via the formation of hydrogen bonded carbamates/carbamic acid and CO 2 δ- species; the latter are adducts formed between CO 2 and [amineH] + Br - salts that are produced during the amine grafting step.

In this work, a detailed study is conducted to understand how ligand substitution influences the CO 2 and N 2 adsorption properties of two highly crystalline sodalite metal-organic frameworks (MOFs) known as Cu-BTT (BTT -3 = 1,3,5-benzenetristetrazolate) and Cu-BTTri (BTTri -3 = 1,3,5-benzenetristriazolate). The enthalpy of adsorption and observed adsorption capacities at a given pressure are significantly lower for Cu-BTTri compared to its tetrazole counterpart, Cu-BTT. In situ X-ray and neutron diffraction, which allow visualization of the CO 2 and N 2 binding sites on the internal surface of Cu-BTTri, provide insights into understanding the subtle differences. As expected, slightly elongated distances between the open Cu 2+ sites and surface-bound CO 2 in Cu-BTTri can be explained by the fact that the triazolate ligand is a better electron donor than the tetrazolate. The more pronounced Jahn-Teller effect in Cu-BTTri leads to weaker guest binding. The results of the aforementioned structural analysis were complemented by the prediction of the binding energies at each CO 2 and N 2 adsorption site by density functional theory calculations. In addition, variable temperature in situ diffraction measurements shed light on the fine structural changes of the framework and CO 2 occupancies at different adsorption sites as a function of temperature. Finally, simulated breakthrough curves obtained for both sodalite MOFs demonstrate the materials' potential performance in dry postcombustion CO 2 capture. The simulation, which considers both framework uptake capacity and selectivity, predicts better separation performance for Cu-BTT. The information obtained in this work highlights how ligand substitution can influence adsorption properties and hence provides further insights into the material optimization for important separations., Competing Interests: The authors declare no competing financial interest.

Metal-organic frameworks (MOFs) are porous, tunable crystalline materials that are attracting widespread scientific attention for their potential use in post-combustion CO2 capture. In this work, we report the synthesis of a new ligand, 1,3-bis(4-carboxyphenyl)-4,5-dihydro-1H-imidazol-3-ium tetrafluoroborate, H2Sp5-BF4, that is subsequently used for the construction of a novel MOF, Cu-Sp5-EtOH. This highly crystalline material has a charged framework that is expected to give rise to high CO2/N2 selectivity. However, the pores of the parent structure could not be accessed due to the presence of strongly coordinated ethanol molecules. After solvent exchange with methanol and subsequently heating Cu-Sp5-MeOH under vacuum, we are able to liberate the solvent providing other small molecules like CO2 access to the inside of the now porous structure, Cu-Sp5. The combination of open metal sites and framework charge leads to an exceptionally high CO2/N2 selectivity, as determined by Ideal Adsorbed Solution Theory (IAST) calculations performed on single-component adsorption isotherms. The CO2/N2 selectivity of Cu-Sp5 reaches a value of over 200 at pressures typically found in post-combustion flue gas (0.15 bar CO2/0.85 bar N2), a value that is among the highest reported to date.