Issue 12, 2022

Incorporation of free halide ions stabilizes metal–organic frameworks (MOFs) against pore collapse and renders large-pore Zr-MOFs functional for water harvesting

Abstract

Chemically and hydrolytically stable MOFs have shown promising water-vapor adsorption properties. However, MOFs that can simultaneously satisfy the following three requirements for effective water harvesting from low-humidity air are quite rare: (1) high water-uptake capacity; (2) hydrolytic and mechanical stability; (3) complete uptake at ∼20–30% relative humidity (RH). Here we show that incorporating free halide ions is effective for enabling a representative Zr-MOF to meet these requirements for water harvesting. As-synthesized MOF-808 initially exhibits very good capacity at RH ≥ 30%, but quickly suffers large capacity losses due to water-evacuation-induced pore collapse. Via a framework-charging and free counter-ion inclusion approach, we were able to replace node-ligated formate anions with charge-neutral aqua ligands and site desired water-sorbing free-halide ions within the large pores of MOF-808. Altered samples show increased gravimetric water uptake, show beneficial shifts of water sorption isotherms toward lower water-vapor partial pressure, eliminate undesirable sorption/desorption isotherm hysteresis, and render MOF-808-Br indefinitely recyclable for ambient-temperature uptake of water vapor and lower-temperature liquid-water release.

Graphical abstract: Incorporation of free halide ions stabilizes metal–organic frameworks (MOFs) against pore collapse and renders large-pore Zr-MOFs functional for water harvesting

Supplementary files

Article information

Article type
Communication
Submitted
29 Du 2021
Accepted
23 Cʼhwe. 2022
First published
23 Cʼhwe. 2022

J. Mater. Chem. A, 2022,10, 6442-6447

Author version available

Incorporation of free halide ions stabilizes metal–organic frameworks (MOFs) against pore collapse and renders large-pore Zr-MOFs functional for water harvesting

Z. Lu, J. Duan, L. Du, Q. Liu, N. M. Schweitzer and J. T. Hupp, J. Mater. Chem. A, 2022, 10, 6442 DOI: 10.1039/D1TA10217F

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