A sunlight-responsive metal–organic framework system for sustainable water desalination

Abstract

Light-responsive materials with high adsorp on capacity and sunlight-triggered regenerability are highly desired for low-cost and environmentally friendly industrial separa on processes. Here we report a poly(spiropyran acrylate) (PSP) func onalized metal-organic framework (MOF) as sunlight-regenerable ion adsorbent for sustainable water desalina on. Under dark condi ons, the zwi erionic isomer quickly adsorbs mul ple ca ons and anions from water within 30 minutes with high ion adsorp on loading up to 2.88 mmol•g −1 . With sunlight illumina on, the neutral isomer rapidly releases these adsorbed salts within 4 minutes. Single-column desalina on experiments show that PSP-MOF works efficiently for desalina ng saline water. A fresh water yield of 1 139.5 L•kg −1 •per day and a low energy consump on of 0.11 Wh•L −1 would be reached for desalina ng 2,233 ppm synthe c brackish water. Importantly, this adsorbent shows excellent stability and cycling performance. This work opens up a new direc on for designing responsive materials for energy-efficient and sustainable desalina on and water purifica on.Desalina on has been increasingly used to address the escala ng water shortage. Its popularity is due to the wide availability of brackish water and seawater, but even more because desalinated produc on is reliable, easily incorporated into the exis ng urban water supply systems, and has minimal health risks 1,2 . Thermal desalina on processes by evapora on, such as mul -stage flash (MSF) and mul ple effect dis lla on (MED), are widely used to produce fresh water. However, these thermal technologies are highly energy-intensive, e.g., 14-27 kWh•m −3 for MSF or MED, because a minimum latent heat of 2260 kJ•kg −1 is essen al for the vaporiza on of subcooled water 3,4 . An alterna ve approach is to take mineral ions out of salt waters using separa ng mediums, e.g., semipermeable membranes or adsorbents 2,5 . By membrane-based techniques, such as the dominant desalina on technology of reverse osmosis (RO), it consumes a much lower energy of 1.5-2.5 kWh•m −3 for trea ng brackish water, and 4-6 kWh•m −3 for seawater desalina on 4 .However, RO has some drawbacks such as rela vely high energy consump on, and chemical usage in membrane cleaning and dechlorina on 4,6 . Membrane dis lla on as another membrane process requires over 100 kWh•m -3 thermal energy, but it consumes around 1.0 kWh•m -3 of electricity if waste heat or renewable hea ng energy is u lized 7 . Electrochemical process, such as electrodialysis (ED) and capaci ve deioniza on (CDI), are also compe ve

Heterometallic Actinide‐Containing Photoresponsive Metal‐Organic Frameworks: Dynamic and Static Tuning of Electronic Properties

“…The spiropyran→merocyanine conversion inside a framework upon 365‐nm excitation resulted in a bathochromic shift ( λ max =570 nm) detected in the DR profile as shown in Figures S19–S23 (Supporting Information). The observed changes are in line with previous reports for spiropyran‐based materials [44–49] . Using the collected DR data, we also performed a Tauc plot analysis for evaluation of changes in the optical band gap under the assumption of direct allowed transitions [30, 50–52] .…”

Heterometallic Actinide‐Containing Photoresponsive Metal‐Organic Frameworks: Dynamic and Static Tuning of Electronic Properties

“…Theo bserved changes are in line with previous reports for spiropyran-based materials. [44][45][46][47][48][49] Using the collected DR data, we also performed aT auc plot analysis for evaluation of changes in the optical band gap under the assumption of direct allowed transitions. [30,[50][51][52] As ar esult, by fitting the linear region of the Tauc plots to the onset of the photon energy,werevealed that the optical band gap narrows upon exposure to one minute of UV-irradiation for photoresponsive frameworks (Figure 3, Figures S19-S23, and Table S2).…”

Abnormal Properties of Low‐Dimensional Confined Water

“…[ 105 ] Besides, it also shows attractive application prospects in the field of seawater desalination. [ 106 ] Yu et al. fabricated a hierarchically nanostructured gel which could achieve a record high solar vapor generation rate of 3.2 kg m −2 h −1 , with an energy efficiency of up to ≈94%.…”