Modulation of Topological Structures and Adsorption Properties of Copper-Tricarboxylate Frameworks Enabled by the Effect of the Functional Group and Its Position

Abstract

To push forward the structural development and fully explore the potential utility, it is highly desired but challenging to regulate in a controllable manner the structures and properties of MOFs. In this work, we reported the structural and functional modulation of Cu(II)-tricarboxylate frameworks by employing a strategy of engineering the functionalities and their positions. Two pairs of unsymmetrical biaryl tricarboxylate ligands modified with a methyl group and a pyridinic-N atom at distinct positions were logically designed and synthesized, and their corresponding Cu(II)-based MOFs were solvothermally constructed. Diffraction analyses revealed that the variation of functionalities and their positions furnished three different types of topological structures, which we ascribed to the steric effect exerted by the methyl group and the chelating effect involving the pyridinic-N atom. Furthermore, gas adsorption studies showed that three of them are potential candidates as solid separation media for acetylene (C 2 H 2 ) purification, with the separation potential tailorable by altering functionalities and their locations. At 106.7 kPa and 298 K, the C 2 H 2 uptake capacity varies from 64.1 to 132.4 cm 3 (STP) g −1 , while the adsorption selectivities of C 2 H 2 over its coexisting components of CO 2 and CH 4 fall in the ranges of 3.28−4.60 and 14.1−21.9, respectively.

Ligand Conformation Fixation Strategy for Expanding the Structural Diversity of Copper-Tricarboxylate Frameworks and C2H2 Purification Performance Studies

“…It should be mentioned that only a few of copper-carboxylate inorganic nodes were reported in copper-pure carboxylate framework compounds to date, including mononuclear Cu(COO) 4 , 45 binuclear Cu 2 (COO) 4 , 23 and trinuclear Cu 3 (COO) 6 . 46 The distance between the copper and carboxylate oxygen atoms is in the range of 1.929−2.161 Å, which is normal compared to the literature values. 47 As for the organic linkers, due to the strong steric hindrance exerted by dual side groups, the biphenyl tricarboxylate ligands exhibit only one almost orthogonal conformation, which is different from our previously reported case in which the mono-methoxyfunctionalized ligand still displays three dissimilar conformations.…”

Partial Linker Substitution Strategy to Construct a Quaternary HKUST-like MOF for Efficient Acetylene Storage and Separation

“…The IAST selectivity of FUT-1a at ambient conditions is lower than that of famous materials HOF-3a (21), 36 CuI@UiO-66-(COOH) 2 (185), 37 SIFSIX-dps-Cu (1787), 38 ATC-Cu (53.6), 30 and slightly lower than that of HKUST-1 (5.84), 11,39 but higher than many other MOFs such as FJU-6-TATB (3.1), 40 CAU-23 (3.8), 41 JXNU-11 (Fe 2 Ni) (2.7), 42 and ZJNU-112 (3.28). 43 Some comparative values of C 2 H 2 capture and isosteric enthalpy are shown in Figure 3f, from which it can be seen that although many MOFs have a high C 2 H 2 uptake, those with a low isosteric enthalpy still have low values.…”

Racemic Porous Organic Cage Crystal with Selective Gas Adsorption Behaviors

“…The value for C 2 H 2 /CH 4 (50/50) separation at 1.0 bar and 298 K are slightly lower than MOFs such as ZJU-199 (27.3) [69] and ZJNU-114 (21.9). [70] At 298 K, the selectivity of CO 2 /CH 4 (50/50) is comparable to those organic crystal such HOF-5 (5.0) [71] and SOF-1a (above 2.0, Henry's Law selectivity). [72]…”