Tailoring PVDF Membranes Surface Topography and Hydrophobicity by a Sustainable Two-Steps Phase Separation Process

This work validates a sustainable way to produce customized PVDF membranes, suitable for contactors applications, in which DMSO is employed as nonhazardous solvent, in place of substances of very high concern (SVHC), by a combination of vapor-induced and liquid-induced phase separation (VIPS and LIPS) stages, and without using any chemical additive as pore forming. The experimental results highlight the key role of the kinetic and thermodynamic parameters of the phase separation processes involved in the control of the surface and transport properties of the PVDF membranes. Namely, combining VIPS and LIPS techniques in a controlled way, allowed to produce symmetric porous membranes with customized rough surface topography (root-mean-square roughness up to 0.67 μm) and hydrophobicity (water contact angle up to 140°) according to a biomimetic behavior as that of lotus leaves surfaces, through an environmental friendly fabrication process. The resulting membranes are characterized by a high porosity (total porosity ≥70%, mean pore size 0.08–0.4 μm), with well interconnected pores, despite no pore former additives were included in the dope solution, making them ideal candidates for application in membrane contactors. The quality of the produced membrane (permeate flux up to 12.1 kgh^1–m^–2 with salt rejection 99.8%) is assessed by MD tests and results showed comparable performance to commercial PVDF membranes having similar mean pore size, porosity and surface roughness, but produced using SVCH solvents

Selective Guest Inclusion in Oxalate-Based Iron(III) Magnetic Coordination Polymers

The preparation and structural characterization of four novel oxalate-based iron­(III) compounds of formulas {(MeNH₃)₂[Fe₂(ox)₂Cl₄]·2.5H₂O}_<i>n</i> (<b>1</b>), K­(MeNH₃)­[Fe­(ox)­Cl₃(H₂O)] (<b>2</b>), {MeNH₃[Fe₂(OH)­(ox)₂Cl₂]·2H₂O}_<i>n</i> (<b>3</b>), and {(H₃O)­(MeNH₃)­[Fe₂O­(ox)₂Cl₂]·3H₂O}_<i>n</i> (<b>4</b>) (MeNH₃⁺ = methylammonium cation and H₂ox = oxalic acid) are reported here. <b>1</b> is an anionic waving chain of oxalato-bridged iron­(III) ions with peripheral chloro ligands, the charge balance being ensured by methylammonium cations. <b>2</b> is a mononuclear complex with a bidentate oxalate, three terminal chloro ligands, and a coordinated water molecule achieving the six-coordination around each iron­(III) ion. Its negative charge is balanced by potassium­(I) and methylammonium cations. <b>3</b> and <b>4</b> are made up of oxalate-bridged and either hydroxo (<b>3</b>)- or oxo-bridged (<b>4</b>) iron­(III) chiral three-dimensional (3D) networks of formulas [Fe₂(OH)­(ox)₂Cl₂]_<i>n</i>^<i>n</i>− (<b>3</b>) and [Fe₂O­(ox)₂Cl₂]_<i>n</i>^2<i>n</i>− (<b>4</b>) with methylammonium (<b>3</b> and <b>4</b>) and hydronium (<b>4</b>) as counterions. The common point these compounds share is related to their synthetic strategy, which consists of the use of mixed alkaline/alkylammonium cations as templating agents for the growth of the 1D or 3D iron­(III) motifs. Interestingly, even in the presence of any given alkaline cation in the reaction solutions, the resulting coordination polymers (<b>1</b>, <b>3</b>, and <b>4</b>) exclusively contain the methylammonium cation, revealing the highly selective character of the 1D and 3D networks. Furthermore, the isolation of the very unstable compound <b>1</b> could be only achieved in the presence of the KCl salt, suggesting a probable templating effect of the potassium­(I) cations. Finally, a study of the variable-temperature magnetic properties of the 3D compounds <b>3</b> and <b>4</b> showed the occurrence of weak ferromagnetic ordering due to a spin canting, the value of the critical temperature (<i>T</i>_c) being as high as 70 K

Selective Guest Inclusion in Oxalate-Based Iron(III) Magnetic Coordination Polymers

The preparation and structural characterization of four novel oxalate-based iron­(III) compounds of formulas {(MeNH₃)₂[Fe₂(ox)₂Cl₄]·2.5H₂O}_<i>n</i> (<b>1</b>), K­(MeNH₃)­[Fe­(ox)­Cl₃(H₂O)] (<b>2</b>), {MeNH₃[Fe₂(OH)­(ox)₂Cl₂]·2H₂O}_<i>n</i> (<b>3</b>), and {(H₃O)­(MeNH₃)­[Fe₂O­(ox)₂Cl₂]·3H₂O}_<i>n</i> (<b>4</b>) (MeNH₃⁺ = methylammonium cation and H₂ox = oxalic acid) are reported here. <b>1</b> is an anionic waving chain of oxalato-bridged iron­(III) ions with peripheral chloro ligands, the charge balance being ensured by methylammonium cations. <b>2</b> is a mononuclear complex with a bidentate oxalate, three terminal chloro ligands, and a coordinated water molecule achieving the six-coordination around each iron­(III) ion. Its negative charge is balanced by potassium­(I) and methylammonium cations. <b>3</b> and <b>4</b> are made up of oxalate-bridged and either hydroxo (<b>3</b>)- or oxo-bridged (<b>4</b>) iron­(III) chiral three-dimensional (3D) networks of formulas [Fe₂(OH)­(ox)₂Cl₂]_<i>n</i>^<i>n</i>− (<b>3</b>) and [Fe₂O­(ox)₂Cl₂]_<i>n</i>^2<i>n</i>− (<b>4</b>) with methylammonium (<b>3</b> and <b>4</b>) and hydronium (<b>4</b>) as counterions. The common point these compounds share is related to their synthetic strategy, which consists of the use of mixed alkaline/alkylammonium cations as templating agents for the growth of the 1D or 3D iron­(III) motifs. Interestingly, even in the presence of any given alkaline cation in the reaction solutions, the resulting coordination polymers (<b>1</b>, <b>3</b>, and <b>4</b>) exclusively contain the methylammonium cation, revealing the highly selective character of the 1D and 3D networks. Furthermore, the isolation of the very unstable compound <b>1</b> could be only achieved in the presence of the KCl salt, suggesting a probable templating effect of the potassium­(I) cations. Finally, a study of the variable-temperature magnetic properties of the 3D compounds <b>3</b> and <b>4</b> showed the occurrence of weak ferromagnetic ordering due to a spin canting, the value of the critical temperature (<i>T</i>_c) being as high as 70 K