Effects of Protonation, Hydroxylamination, and Hydrazination of g-C3N4 on the Performance of Matrimid®/g-C3N4 Membranes

Abstract

One of the challenges to continue improving polymeric membranes properties involves the development of novel chemically modified fillers, such as nitrogen-rich 2-D nanomaterials. Graphitic carbon nitride (g-C3N4) has attracted significant interest as a new class of these fillers. Protonation is known to afford it desirable functionalities to form unique architectures for various applications. In the work presented herein, doping of Matrimid® with protonated g-C3N4 to yield Matrimid®/g-C3N4 mixed matrix membranes was found to improve gas separation by enhancing the selectivity for CO2/CH4 by up to 36.9% at 0.5 wt % filler doping. With a view to further enhancing the contribution of g-C3N4 to the performance of the composite membrane, oxygen plasma and hydrazine monohydrate treatments were also assayed as alternatives to protonation. Hydroxylamination by oxygen plasma treatment increased the selectivity for CO2/CH4 by up to 52.2% (at 2 wt % doping) and that for O2/N2 by up to 26.3% (at 0.5 wt % doping). Hydrazination led to lower enhancements in CO2/CH4 separation, by up to 11.4%. This study suggests that chemically-modified g-C3N4 may hold promise as an additive for modifying the surface of Matrimid® and other membranes.

Molecular Design of Two-Dimensional Covalent Heptazine Frameworks for Photocatalytic Overall Water Splitting under Visible Light

“…However, the peak intensities corresponding to the heptazine rings are slightly reduced under light irradiation, indicating that the heptazine rings are involved in the photocatalytic reaction . Meanwhile, the peak at 3154 cm –1 can be assigned to the N–H bonds as shown in Figure S15b, confirming that HER reduction pathway processes occurred on heptazine rings of H@DBTD as evidenced by first-principles calculations, which have been discussed previously . Moreover, several new IR bands develop in the range of 1000–1300 cm –1 after photoirradiation as shown in Figure S15c.…”

“…64 Meanwhile, the peak at 3154 cm −1 can be assigned to the N−H bonds as shown in Figure S15b, confirming that HER reduction pathway processes occurred on heptazine rings of H@DBTD as evidenced by first-principles calculations, which have been discussed previously. 65 Moreover, several new IR bands develop in the range of 1000−1300 cm −1 after photoirradiation as shown in Figure S15c. The newly emerged IR peaks at 1072 and 1280 cm −1 can be attributed to the characteristic C−O stretching mode in C−OH and C−O−C, respectively.…”

Synthesis and applications of graphitic carbon nitride (g-C3N4) based membranes for wastewater treatment: A critical review

“…This method involves the application of a g–C 3 N 4 –based layer to the membrane surface either by coating it or by grafting [ 49 ]. For designing g–C 3 N 4 –based hybrid membranes, several surface modification methods have been used, including self-assembly (using UV/plasma/chemical agents), vacuum filtration (using chemical agents), dip coating (using cross-linking), interfacial polymerization (using electrospinning), and grafting (using chemical agents) [ [50] , [51] , [52] ]. The most widely utilized technique is vacuum filtration because it is a quick way to make consistent g–C 3 N 4 –based composites on substrate materials.…”

Fast hydrogen purification through graphitic carbon nitride nanosheet membranes

“…Graphitic carbon nitride (g-C 3 N 4 ) nanosheets, hosting high-density molecular-sized pores composed of tri-s-triazine units in the entire 2D plane 14,15 , are considered ideal building blocks for molecular sieving membrane. Benefits to the nanometer-thin thickness and high-density nanopores, g-C 3 N 4 nanosheet membranes should be a superior candidate for H 2 separation 16,17 , which was already proved by theoretical investigations. For instance, Li et al 18 found that H 2 had the lowest diffusion barrier to go through the g-C 3 N 4 nanosheets by density functional theory (DFT) calculations, which resulted in a superior selectivity between H 2 and other larger gases.…”