Emergence of the Janus-MOF (J-MOF) Boat as a Nascent Amalgamation in the Arena of Photothermal Desalination

Abstract

The diminution of potable water is a pressing issue in several countries and is the most prioritized obligation of environmental scientists. Thence, the ardent emergence of photothermal interfacial evaporation (PTIE) is seen as a neoteric horizon in the avenue of water remediation. Consequently, for the first time, the decoration of metal–organic frameworks (MOFs) over a Janus architecture as an avant-garde marriage was explored in the domain of photothermal desalination. In this study, a solar absorber was developed by inducing phase change to Ni-doped HKUST-1 (Cu-MOF) via high-temperature calcination to create biphasic CuO/Cu2O caged in N-doped graphene oxide (NGO) sheets. The doping of Ni in the framework demonstrated to enhance the pyrrolic nitrogen (PN) of NGO sheets, which improved the photothermal feature of the solar absorber in union with promoting Cu2+ species as well as enriching the p-type nature of the biphasic configuration for augmented nonradiative relaxation of electrons. In order to take advantage of the robust potential of the designed solar absorber, it was coated over a Janus membrane prepared via the facile approach, composed of poly(methyl methacrylate) (PMMA) and agarose gel having opposing wettability, referred to as the J-MOF boat. This nascent amalgamation recorded a maximum evaporation rate of 1.5 kg/m2 h with pure water and 1.3 kg/m2 h with simulated seawater under 1 sun irradiation. This phenomenon was ascribed to the highly porous agarose layer to facilitate extraordinary water pumping, while concomitantly rejecting salts via capillary action in a nature-mimicking fashion as seen in mangrove trees. The boat-like feature arises from the PMMA layer to conduct PTIE at the water/air interface by uniformly dispersing the localized heat from the solar absorber owing to its low thermal conductivity and three-dimensional (3D) porous structure. Thus, it is believed that this nascent strategy could push the boundaries of solar-driven desalination.

The Design of PAN-Based Janus Membrane with Adjustable Asymmetric Wettability in Wastewater Purification

“…Janus membrane is a general term for membranes with opposite properties, such as composition, morphology, wettability, surface charge, and so on. Layerby-layer electrospinning, surface coating, unilateral deposition and chemical modification are often used to prepare Janus membranes [29][30][31][32]. In recent years, Janus membranes with a unique hierarchical structure of asymmetric hydrophilicity/hydrophobicity have attracted more and more attention [33,34].…”