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MOF water harvester produces water from Death Valley desert air in ambient sunlight
Summary:
The authors from University of California, Berkeley, USA; Pohang University of Science and Technology (POSTECH), South Korea developed MOF-303 and MOF₈₅-G₁₅ materials with high water uptake, good thermal conductivity, achieving efficient passive atmospheric water harvesting in Death Valley and Berkeley.
Background:
1. To address global water scarcity (5 billion people to face water stress by 2050) and limited off-grid water tech, previous researchers developed MOF/porous polymer-based atmospheric water harvesting (AWH) systems, but most need power; only one passive system was tested in deserts with low yield.
2. The authors proposed a passive MOF water harvester with optimized MOF cartridge (constant volume-surface ratio) and condenser (hydrophobic coating), doubling water yield vs prior passive systems.
Research Content:
1.Synthesis
- MOF-303: Dissolved H₂PZDC in water, added NaOH, sonicated, mixed with AlCl₃·6H₂O, heated at 100°C for 24h, centrifuged, washed (water/methanol), dried, activated at 150°C.
- MOF₈₅-G₁₅: Mixed activated MOF-303 (85wt%) with graphite (15wt%), ground, pressed at 78MPa for 2min.
2.Characterizations
1) BET: MOF₈₅-G₁₅ has 955 m²/g BET surface area (1120 m²/g for MOF-303 component); MOF100 (no graphite) has 1200 m²/g, M95-G5 1080 m²/g, M90-G10 1130 m²/g.
2) SEM: MOF₈₅-G₁₅ shows intact pellet structure; stable in water for 24h (vs cellulose-bound MOF85-C15 which dissociates).
3) Other tests: PXRD confirms MOF-303 crystal structure in pellets; FT-IR shows MOF-303 functional groups retained; contact angle: Al (66°±2.8°), PTFE (103°±1.1°), CNF/PTFE (144°±0.5°).
3.Application
- Lab test: 35g MOF-303 cartridge harvested 5.5-8.71g water (157-248 g H₂O/kg MOF-303).
- Field test: Berkeley (June): 285/210 g H₂O/kg MOF-303; Death Valley (Aug): 114-210 g H₂O/kg MOF-303 (even at 14% RH, 60°C).
4.Mechanism
- Night: MOF cartridge adsorbs atmospheric water via porous structure (MOF-303 inflection point at 12% RH).
- Day: Solar heating (MOF temp up to 70°C) desorbs water; vacuum-insulated housing reduces heat loss; condenser (top-placed) uses air density gradient for vapor transport; hydrophobic coating accelerates dropwise condensation.
Outlook:
This research achieves high-yield passive AWH (285 g H₂O/kg MOF-303) under extreme conditions, provides off-grid water solutions for arid regions, and guides optimization of AWH device design and sorbent synthesis.
MOF water harvester produces water from Death Valley desert air in ambient sunlight
Authors: Woochul Song, Zhiling Zheng, Ali H. Alawadhi, Omar M. Yaghi
DOI: 10.1038/s44221-023-00103-7
Link: https://www.nature.com/articles/s44221-023-00103-7
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