A porous Zn-based metal-organic framework with an expanded tricarboxylic acid ligand for effective CO2 capture and CO2/CH4 separation

Improved structure of Zr-BTC metal organic framework using NH2 to enhance CO2 adsorption performance

Modified mesoporous NH2-Zr-BTC mixed ligand MOF nanocomposites were synthesized via the hydrothermal method as a novel adsorbent for CO2 capture. The newly modified MOF-808 with NH2 demonstrated a similar mesoporous morphology as MOF-808, whereas the specific surface area, pore volume, and average particle size, respectively, increased by 15%, 6%, and 46% compared to those of MOF-808. The characterization analyses exhibited the formation of more active groups on the adsorbent surface after modification. In addition, a laboratory adsorption setup was used to evaluate the effect of temperature, pressure, and NH2 content on the CO2 adsorption capacity in the range of 25-65 °C, 1-9 bar, and 0-20 wt%, respectively. An increase in pressure and a decrease in temperature enhanced the adsorption capacity. The highest equilibrium adsorption capacity of 369.11 mg/g was achieved at 25 °C, 9 bar, and 20 wt% NH2. By adding 20 wt% NH2, the maximum adsorption capacity calculated by the Langmuir model increased by about 4% compared to that of pure MOF-808. Moreover, Ritchie second-order and Sips models were the best-fitted models to predict the kinetics and isotherm data of CO2 adsorption capacity with the high correlation coefficient (R2 > 0.99) and AARE% of less than 0.1. The ΔH°, ΔS°, and ΔG° values were - 17.360 kJ/mol, - 0.028 kJ/mol K, and - 8.975 kJ/mol, respectively, demonstrating a spontaneous, exothermic, and physical adsorption process. Furthermore, the capacity of MH-20% sample decreased from 279.05 to 257.56 mg/g after 15 cycles, verifying excellent stability of the prepared mix-ligand MOF sorbent.

Synthesis and Characterization of Zn-Carboxylate Metal–Organic Frameworks Containing Triazatruxene Ligands

Reactions between triazatruxene-based tricarboxylate ligands, H3tat-R, and zinc nitrate under solvothermal conditions afforded new metal–organic frameworks (MOFs) with the general formula [Zn3(tat-R)2(H2O)2], MUF-tat-R (R=a hydrocarbon substituent on the triazatruxene nitrogen atoms). Single-crystal X-ray diffraction analysis revealed that these frameworks are 3D networks with a (10,3)-a topology. Linear trinuclear zinc clusters are connected to tat ligands to form chiral channels that accommodate the substituents on the tat ligands. MUF-tat and MUF-tat-benzyl crystallize in a cubic crystal system whereas MUF-tat-butyl and MUF-tat-hexyl are tetragonal. MUF-tat-benzyl retains its porosity on activation, which was confirmed by gas adsorption studies.

Controlled interpenetration of 44 networks: syntheses and structures of two Cu3-cluster coordination polymers

The reaction of copper nitrate and triethanolamine with benzene-1,4-dicarboxylic acid (bdcH₂) or 4,4'-[1,4-phenylenebis(oxy)]dibenzoic acid (podaH₂) leads to the formation of poly[bis(μ₄-benzene-1,4-dicarboxylato-κ⁴O¹:O^1':O⁴:O⁴)bis{μ₂-[bis(2-hydroxyethyl)amino]ethanolato-κ⁴N,O,O',O'':κO}tricopper(II)], [Cu₃(C₈H₄O₄)₂(C₆H₁₄NO₃)₂] or [Cu₃(μ₄-bdc)₂(teaH₂)₂] (I), and poly[bis{μ₄-4,4'-[1,4-phenylenebis(oxy)]dibenzoato-κ⁴O:O':O'':O''}bis{μ₂-[bis(2-hydroxyethyl)amino]ethanolato-κ⁴N,O,O',O'':κO}tricopper(II)], [Cu₃(C₂₀H₁₂O₆)₂(C₆H₁₄NO₃)₂] or [Cu₃(μ₄-poda)₂(teaH₂)₂], (II). The two representative compounds contain a well-established Cu₃ cluster supporting a given 4⁴ network. The ligand length is the underlying factor that controls the degree of interpenetration. Controlled interpenetration can be facile to realise by elongating protocols. Compound I shows a non-interpenetrating 4⁴ network, whereas II features a threefold interpenetrating network. Furthermore, similar hydrogen-bond interactions extend the different interpenetrating 4⁴ networks into three-dimensional supramolecular topologies. Variable-temperature magnetic studies showed a ferromagnetic coupling behaviour in the two complexes.