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Broadly Tunable Atmospheric Water Harvesting in Multivariate Metal−Organic Frameworks
Summary:
The authors from the University of California, Berkeley, USA, and King Abdulaziz City for Science and Technology, Saudi Arabia developed multivariate metal-organic frameworks (PT-MOFs) with broad tunability in humidity adaptation, regeneration temperature, and adsorption enthalpy, achieving high-yield, scalable synthesis and efficient performance in atmospheric water harvesting.
Background:
1. To address global water scarcity, especially in arid regions, previous researchers deployed metal-organic frameworks (MOFs) like MOF-303 for atmospheric water harvesting, yet existing MOFs lacked sufficient tunability to adapt to diverse environmental conditions and faced challenges in large-scale synthesis with high yields.
2. The authors proposed an innovative multivariate strategy, introducing thiophene-2,5-dicarboxylate (TDC²⁻) into MOF-303’s backbone with 1H-pyrazole-3,5-dicarboxylate (PZDC²⁻) to prepare PT-MOFs, realizing broader performance tunability and scalable, high-yield synthesis.
Research Content:
1.Synthesis:
- Solvothermal method: Dissolved H₂PZDC and H₂TDC in NaOH solution, added AlCl₃ solution, incubated at 100 °C for 2–4 days, with yields of 47–50% (PT26 adjusted to 2.5 eq. base gave 78%).
- Reflux method (flask): Mixed H₂PZDC, H₂TDC, and NaOH, added AlCl₃ dropwise, refluxed at 120 °C for 3–40 hours, yields ≥90%.
- Scalable synthesis (200 L vessel): Dissolved reactants in water, added AlCl₃, refluxed at 100 °C for 6 hours, each batch produced ~3.5 kg activated MOF, yields 84–91%.
2.Characterizations:
1) BET: Solvothermal PT-MOFs had BET surface areas 1217.4–1372.0 m²/g; reflux (flask) ones 1199–1374 m²/g; scalable ones 1120.4–1392 m²/g. Pore volumes (DFT) 0.453–0.503 cm³/g, pore sizes 9.4–9.6 Å.
2) SEM/EDS: MOF-303-like phases (PT80-PT26) and CAU-23-like phases (PT17-PT08) had distinct morphologies; EDS confirmed uniform distribution of Al, O, C, N (from PZDC²⁻), and S (from TDC²⁻) in crystals.
3) TGA: MOF-303-like PT-MOFs stable up to ~400 °C (Ar/air); CAU-23-like ones decomposed at ~375 °C. Water sorption: PT80 adsorbed at 12% RH, PT08 at 27% RH; water uptake 0.42–0.45 g/g; adsorption enthalpy Δhads -48.6 to -54.2 kJ/mol.
3.Application:
Tested in atmospheric water harvesting: PT-MOFs adapted to 12–27% RH; at 1.70 kPa, desorption temperature可调 by >14 °C; low hysteresis ensured energy efficiency, suitable for arid conditions.
4.Mechanism:
- Multivariate strategy: TDC²⁻ (hydrophobic) mixed with PZDC²⁻ (hydrophilic) adjusted pore hydrophilicity, thus tuning humidity cutoff, adsorption enthalpy, and regeneration temperature.
- Time-dependent formation: PT26-HY transformed from CAU-23-type to MOF-303-type with extended reflux, due to gradual crystallization equilibrium, without changing linker ratio.
Outlook:
This research developed PT-MOFs with broad performance tunability for atmospheric water harvesting, solved low-yield and non-scalable synthesis issues, and laid a foundation for commercializing MOF-based water-harvesting technology and large-scale atmospheric moisture extraction.
Broadly Tunable Atmospheric Water Harvesting in Multivariate Metal−Organic Frameworks
Authors: Zhiling Zheng, Nikita Hanikel, Hao Lyu, Omar M. Yaghi*
DOI: 10.1021/jacs.2c09756
Link: https://pubs.acs.org/doi/10.1021/jacs.2c09756
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