Rational synthesis and characterization of porous Cu(ii) coordination polymers

Abstract

Porous coordination polymers or metal-organic frameworks constructed from metal ions and organic ligands have attracted much attention as next-generation porous materials due to their high designability, regularity, flexibility, and porosity. In particular, the Cu(II) ion with Jahn-Teller distortion can offer unique functions (coordination flexibility, Lewis acid property, and polarity) to porous frameworks. In this Perspective, we focus on porous Cu(II) coordination polymers; their unique characteristics and potential future applications are illustrated by recent experimental results.

Diverse structures and adsorption properties of quasi-Werner-type copper(ii) complexes with flexible and polar axial bonds

“…As a result, the differences for the Cu II complexes are also slightly higher than those for the Ni II complexes. Hence, the PF 6 -anion indeed enhances the adsorption potential, compared with the NCS -anion. In real crystals, a gas molecule is probably incorporated in space surrounded by several discrete complexes, which means that the real adsorption potential is further amplified.…”

“…α-1 and α-1′ are the first example that the decrease in crystal size causes a dramatic increase in adsorption capacity. Previously, we have calculated the natural charges and the electrostatic surface potentials mapped onto a surface of total electron density in the unit of α-1 and α-[Ni(NCS) 2 (4-mepy) 4 ], in which the unit of α-1 has a more polar structure than that of α-[Ni(NCS) 2 (4-mepy) 4 ] and the F atoms of the PF 6 -anions possess negative charges. These results imply that the PF 6 -anions act as electron donors and interact with electronacceptor CO 2 molecules.…”

“…We speculate that the large hysteresis curves observed in α-1′ are due to the strong hostguest interactions between the PF 6 -anions and CO 2 molecules. The adsorption potentials around the unit of α-1 and α-[Ni(NCS) 2 (4-mepy) 4 ] were calculated by molecular simulation to elucidate the effect of the PF 6 -anion. As shown in Table 1, the Cu II complexes show slightly higher adsorption potentials for CO 2 and N 2 gases than the Ni II complex.…”

“…As shown in Table 1, the Cu II complexes show slightly higher adsorption potentials for CO 2 and N 2 gases than the Ni II complex. Next, to confirm that such an enhancement is attributed to the PF 6 -anion, the differences between the adsorption potentials in the presence and absence of anions were calculated. As a result, the differences for the Cu II complexes are also slightly higher than those for the Ni II complexes.…”

“…Recently, we have found that the porous Cu II coordination polymer (PCCP) [Cu(PF 6 ) 2 (bpetha) 2 ] n (bpetha = 1,2-bis(4-pyridyl)ethane) with flexible and polar Cu-PF 6 bonds has interesting guestrecognition abilities. 6 This PCCP has polar Cu-PF 6 units in the framework and therefore selectively adsorbs CO 2 and C 2 H 2 gases with Lewis-acid properties via electron donoracceptor interactions. 7a On the other hand, when this PCCP is exposed to Lewis-base guests with sterically less-crowded coordinated atoms, the weakly coordinated PF 6 -anions are easily released from the axial sites and Lewis-base guests attach to these sites instead.…”