Cross-Linking with Diamine Monomers To Prepare Composite Graphene Oxide-Framework Membranes with Varying d-Spacing

Abstract

Three diamine monomers (ethylenediamine, butylenediamine, and p-phenylenediamine) were selected for cross-linking graphene oxide (GO) to prepare composite graphene oxide-framework (GOF) membranes through filtration using a pressure-assisted self-assembly technique. The membranes were applied to separate an ethanol−water mixture by pervaporation. Unmodified GO comprised only hydrogen bonds and π−π interactions, but after cross-linking it with a diamine, attenuated total reflectance−Fourier transform infrared and X-ray photoelectron spectroscopy demonstrated that the diamine was chemically bonded both to GO and the membrane support. Moreover, GO hydrophilicity was substantially altered; water contact angle increased from 24.4°to 80.6°(from cross-linking with an aliphatic structure of diamine to cross-linking with an aromatic structure). Results of X-ray diffraction showed that d-spacing in GOF layers varied from 10.4 to 8.7 Å. For GOFs presoaked in 90 wt % ethanol−water, covalent bonds between the layer and diamine could effectively suppress stretching of d-spacing. Cross-linking with ethylenediamine produced a composite membrane that exhibited a short interlayer dspacing and delivered an excellent pervaporation performance at 80 °C: permeation flux = 2297 g/(m 2 h); water concentration in permeate = 99.8 wt %. The membrane showed stability during a long-term operation at 30 °C for 120 h.

Ultrathin graphene oxide nanosheet membranes with various d -spacing assembled using the pressure-assisted filtration method for removing natural organic matter

“…Crosslinking of the diamine monomers dramatically altered the chemical properties of the GO films. The FTIR spectrum of the original GO membrane suggested the presence of hydroxyl groups (-OH stretching at 3390 cm −1 ), carboxyl groups (C_O stretching at 1727 cm −1 and C-OH stretching at 1380 cm − 1 ), unoxidized C_C bonds (stretching at 1624 cm − 1 ), epoxy groups (C-O-C stretching at 1220 cm −1 ) and alkoxy groups (C-O stretching at 1056 cm − 1 ), which corresponded with the findings of previous studies [9,20,23]. By cross-linking different diamine monomers with GO, the absorption peaks of these oxygencontaining functional groups disappeared or were diminished, especially the hydroxyl, carboxyl and alkoxy functional groups.…”

“…By cross-linking different diamine monomers with GO, the absorption peaks of these oxygencontaining functional groups disappeared or were diminished, especially the hydroxyl, carboxyl and alkoxy functional groups. The diamine monomers reacted with GO, and several bonds were formed, including hydrogen-ionic, and covalent bonds [9]. Although hydrogen and ionic bonds are weak, covalent bonds could maintain their integrity during filtration processes.…”

“…Although several researchers believe that carboxyl groups are mainly attached at the vacancies and edges of GO nanosheets [30], most carboxyl groups remained after the reaction [31]. These aliphatic diamines, such as EDA and PDA, tend to donate electrons, resulting in a high amine electron density and the formation of a strong nucleophile that prioritizes epoxide groups for undergoing nucleophilic addition reactions [9]. Nevertheless, the benzene ring in phenylenediamine has high resonance stability [32] and a large steric hindrance, which reduces the reactivity of the amine and can neither attack carbon on the GO sheet nor result in an open-ring reaction with epoxide [33].…”

“…GO membranes can be fabricated from GO nanosheets by using different methods, including filtration assembly [7][8][9][10], layer-by-layer deposition [11][12][13], and spin coating [14,15]. Among these methods, filtration assembly is facile, effective and frequently used in experiments.…”

Shielding membrane surface carboxyl groups by covalent-binding graphene oxide to improve anti-fouling property and the simultaneous promotion of flux

“…Furthermore, from the Table S1 and Fig. 4b-d, we can also find that during GO functionalization process, the covalent-binding GO on the membrane surface was mainly aided by the eCeNe bonds that formed from the ED and epoxy of the GO (Hung et al, 2014) (see the discussion in Supplementary Information). However, a small amount of eCOOH also formed to amide bond with the ED aided by EDC/NHS (Perreault et al, 2014).…”