Nano-/Micro-confined Water in Graphene Hydrogel as Superadsorbents for Water Purification

Confined water has been proven to be of great importance due to its pervasiveness and contribution to life and many fields of scientific research. However, the control and characterization of confined water are a challenge. Herein, a confined space is constructed by flexibly changing the pH of a graphene oxide dispersion under the self-assembly process of a graphene hydrogel (GH), and the confined space is adjusted with variation from 10.04 to 3.52 nm. Confined water content in GH increases when the pore diameter of the confined space decreases; the corresponding adsorption capacity increases from 243.04 to 442.91 mg g^-1. Moreover, attenuated total reflectance Fourier transform infrared spectroscopy and Raman spectroscopy are utilized to analyze the hydrogen bonding structure qualitatively and quantitatively, and correlation analysis reveals that the improvement in the adsorption capacity is caused by incomplete hydrogen bonding in the confined water. Further, confined water is assembled into four typical porous commercial adsorbents, and a remarkable enhancement of the adsorption capacity is achieved. This research demonstrates the application potential for the extraordinary properties of confined water and has implications for the development of highly effective confined water-modified adsorbents.