Magnetic Field Control of Micropore Formation in [Zn₂(Oxac)(Taz)₂]·(H₂O)_x

Abstract

[Zn 2 (Oxac)(Taz) 2 ]¢(H 2 O) x , referred to as ZOTW x , was prepared from aqueous methanol solutions of Zn 5 (CO 3 ) 2 (OH) 6 and two kinds of ligands, 1,2,4-triazole (Taz) and oxalic acid (Oxac), at 453 K under magnetic fields of up to 6 T. The magnetic fields markedly changed the morphology from irregular agglomerates at zero field to rectangular-prism crystals having smooth surfaces at 6 T, although the monoclinic crystal structure was only slightly deformed to a triclinic one. As-synthesized ZOTW x (H) prepared under magnetic fields of H/T ² 2 adsorbed a large amount of N 2 at 77 K in rectangular Type I adsorption isotherms even without the usual pretreatment at 383 K and 1 mPa. It suggests that high magnetic fields induced the formation of hydrophobic micropores having uniform sizes. The hydrophobicity was consistent with the results that the water-assisted micropore formation was depressed in the as-synthesized ZOTW x (H) containing a small amount of water. Porous coordination polymers (PCPs) are a new class of porous crystalline materials that have extremely high porosity and selective adsorptivity for guest molecules.112 Gas storage capacity in PCPs was promoted by introducing open metal sites, 6 increasing the surface area, 7 and modifying pores with functionalized organic linker.8 The gate-controlled adsorption was found that the latent pores of flexible PCPs opened above a critical pressure.4,9 Such flexible PCPs were brought about after desolvation. The amounts of solvent surrounded by the frameworks of PCPs are very important for the formation of latent pores and their flexibility, as well as pore volume and adsorptivity.We found a new route for micropore formation of one of the PCPs, [Zn 2 (Oxac)(Taz) 2 ]¢(H 2 O) 2.5 referred to as ZOTW 2.5 ; i.e., the micropore formation via water-assisted CO 2 adsorption on ZOTW x .13 Although the as-synthesized ZOTW 2.5 pretreated gently had little open micropores because of some residual water, the water-assisted adsorption of CO 2 to bring about the formation of abundant open micropores after vacuum degassing.Magnetic fields (H/T) drastically modify the structures and properties of materials, especially colloidal systems.1419 Homogeneous magnetic fields affect them thermodynamically via magnetic energy, (1/2)»H 2 , which may induce magnetic orientation, phase transition, etc. The magnetic field gradient also brings about a magnetic force, which causes convection, mass-transport, concentration change, etc. In this study, magnetic field control of the pore formation of a PCP comprising metal ions and magnetically anisotropic ligands was investigated. ZOTW 2.5 was synthesized under magnetic fields of up to 6 T, and the morphology of the crystals, crystal structure, size, and properties of the micropores were examined. The experiments have been described in a previous paper. 13 0.4 g of Zn 5 (CO 3 ) 2 (OH) 6 , 0.4 g of H 2 C 2 O 4 , and 1.4 g of 1,2,4-triazole were added to a mixed solvent of 12 mL of methanol and 2 mL of distilled water. The dispersion was tran...

Pengaruh medan magnet terhadap morfologi dan adsorpsi CO2 pada amine-functionalized Zn-porous coordination polymers

“…Pengangkutan reaktan karena konveksi dapat mengalami depresi karena gradien di medan magnet dan suseptibilitas magnetik dari larutan. (Zubir et al, 2016). Untuk memastikan sifat pori, adsorpsi N2 diukur pada waktu pretreatment 77K dan 12 jam pada suhu 110 o C (Gbr 3).…”

“…Pada penelitian sebelumnya, [Zn2(Oxac)(Taz)2]•(H2O)x, atau ZOTWx, disintesis dari larutan metanol air Zn5(CO3) 2(OH)6, 1,2,4-triazole (Taz) (Li et al, 2006) dan asam oksalat (Oxac) pada 453 K di bawah berbagai kekuatan medan magnet hingga 6 T. (Zubir et al, 2016). Medan magnet berubah secara nyata pada morfologinya dari aglomerat tidak beraturan pada 0T sampai kristal persegi panjang yang memiliki permukaan halus pada 6T, dan struktur kristal monoklininya sedikit berubah bentuk menjadi triklinik.…”

“…Permukaan atau kerangka permukaan mikropori dapat menjadi hidrofobik karena deformasi dalam struktur kristal. (Zubir et al, 2016).…”

Pretreatment and Adsorption Effects on Stability and Morphology Structure of TCNQ-Based Porous Coordination

“…Magnetic field energy can provide the same direction for homogeneous of crystal formation. With the change in the formation of crystals due to magnetic fields could affected the physical properties and chemical properties in interacting with other molecules (Zubir and Ozeki, 2016).Furthermore, we synthesized both of PCPs series under 6T magnetic field and also without applied magnetic field (0T).…”

The Role of Micropores and Amine Groups in Preferential CO2 Adsorptivity of Porous Zn-Coordination Polymers Comprising Mixed Ligands of Triazole and Amino Triazole

“…In previously report, we have explored the new design of PCPs as Zn 2 (C 2 O 4 )(C 2 N 3 H 2 ) 2 . (H 2 O) 2 .5 or Zn-oxac-Taz 12,17 with triazole ligands with no amine groups presence which promoted significant N 2 amount adsorption isotherms and also available space to accept carbon dioxide molecules. If compare with others PCPs as Zn 2 (C 2 O 4 )(C 2 N 4 H 3 ) 2 .…”