Metal–Organic Framework Composite Photothermal Membrane for Removal of High-Concentration Volatile Organic Compounds from Water via Molecular Sieving

Abstract

Water-soluble volatile organic compounds (VOCs) are among the most difficult-to-treat species during wastewater treatment. The current purification and removal of high-concentration VOCs still rely on the energy-consuming distillation and high-pressure driven reverse osmosis technology. There is an urgent need for an advanced technology that can effectively remove high-concentration VOCs from water. Here, we report a metal–organic framework (MOF)/polyaniline (PANI) nanofiber array composite photothermal membrane for removal of high-concentration VOCs from water via molecular sieving during a solar-driven evaporation process. The modified zeolitic imidazole framework-8 (ZIF-8) layer grown on a PANI nanofiber array acts as a molecular sieving layer to evaporate water but intercept VOCs. The composite membrane exhibits high VOCs rejection and a high-water evaporation rate for water containing different concentrations of VOCs. When treating water containing VOCs with a concentration of up to 400 mg L–1, the VOCs rejection rate is up to 99% and the water evaporation rate is 1.0 kg m–2 h–1 under 1 sun irradiation (1 kW m–2). Our work effectively combines the molecular sieve effect with a solar-driven evaporation process, which provides an effective strategy for the treatment of water containing VOCs.

Supramolecular Engineering of Amorphous Porous Polymers for Rapid Adsorption of Micropollutants and Solar‐Powered Volatile Organic Compounds Management

“…Upon irradiation under 1 sun, the wet CTF‐CB‐OX membrane was heated from 22.5 to 45 °C within 2 min, indicating localized heat in the membrane (Figure 5b,c). [ 29,61,62 ] Under 1 sun irradiation, the assembled CTF‐CB‐OX membrane showed efficient solar‐driven water evaporation at a rate of 1.19 kg m −2 h −1 , which was much higher than that of the PVDF membrane under the same condition (0.41 kg m −2 h −1 ) (Figure 5d). As a small VOC pollutant, we selected phenol, which is widely available in wastewater and can cause severe environmental damage.…”

“…[ 23 ] General mechanisms for VOCs removal such as catalytic reaction [ 24–28 ] are most well‐known, but recently, VOCs removal via solar‐driven water evaporation process has been shown to be very effective. [ 29–32 ] Therefore, it is challenging to develop low‐cost photothermal porous polymers that are useful not only for the rapid adsorption of water‐soluble micropollutants but also for VOC rejection via direct solar distillation.…”

Emerging Materials for Interfacial Solar‐Driven Water Purification

“…Accordingly, when dispersed onto a PVDF membrane, PPF‐3 displayed a 1.99 kg m −2 h −1 SVG rate (70.3 % efficiency) under 2 sun, much higher than when just the porphyrin monomer was applied. Still, the sometimes‐observed low water stability impedes the applications of many MOFs to construct solar evaporators [30, 33] . Therefore, the coating of protecting layers was proposed.…”

“…thus fabricated a composite membrane by growing a zeolitic imidazole framework‐8 (ZIF‐8) layer on a PANI‐coated PES membrane, where PANI worked as solar absorber layer (Figure 4c). [30] ZIF‐8 has a larger aperture size (0.34 nm) than the kinetic diameter of water molecules (0.27 nm), but a smaller one than that of most VOCs (usually >0.5 nm), thus could reject VOCs from the evaporated steam. Furthermore, to improve the water stability, ZIF‐8 was modified by a partial ligand‐exchange reaction using a hydrophobic ligand, 5,6‐dimethylbenzimidazole.…”

Metal–Organic Frameworks and Their Composites for Environmental Applications

“…Massive consumption of water makes it more difficult by the increasing population pressures, the vagaries of water use behavior and climate change. [121][122][123][124] Therefore, it is particularly imperative to control water pollution. Nowadays, MOFs have received huge attention as adsorbents for heavy and toxic metal ions with a small size because of their tailorable surface functionalities and high specific surface area.…”