Characterization and chemical analysis
This protocol is extracted from research article:
Practical water production from desert air
Sci Adv, Jun 8, 2018; DOI: 10.1126/sciadv.aat3198

Powder x-ray diffraction (PXRD) patterns of MOF-801, MOF-801/G, MOF-303, and MOF-303/G were recorded with a Bruker D8 ADVANCE diffractometer (Göbel-mirror monochromated Cu Kα1 radiation, λ = 1.54056 Å). Typically, data were collected between 3° and 50° with a step width of 0.01 and a total data collection time of 30 min.

Nitrogen gas adsorption isotherms were recorded on a Quantachrome QUADRASORB-SI volumetric gas adsorption analyzer at 77 K. Volumetric water adsorption isotherms and stability tests were measured on a BEL Japan BELSORP-aqua3, for which the water (analyte) was degassed through three freeze-pump-thaw cycles. Helium gas was used to estimate the dead space for both gas and water adsorption measurements. The framework density of all MOF and MOF/G samples was measured using a pycnometer (Ultrapyc 1200e, Quantachrome). Ultrahigh-purity gases (He and N2; Praxair, 99.999% purity) were used for all experiments.

Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra were recorded on a Bruker ALPHA Platinum ATR-FTIR spectrometer. Diffuse reflectance spectra between 285 and 2500 nm were recorded on a Varian Cary 5000 spectrometer. Absorption spectra between 285 and 3000 nm were recorded using a Shimadzu UV-3600 equipped with a double monochromator having a wavelength range of 185 to 3300 nm. A photomultiplier tube (ultraviolet and visible region) and an InGaAs and cooled PbS detector (long-wavelength detection) were used.

Thermogravimetric analysis (TGA) measurements were performed on a TA Instruments SDT-Q600 series thermal gravimetric analyzer. Gases were humidified by bubbling dry air through a 2-liter bubbler humidifier, and both humidity and temperature were monitored using high-accuracy thermocouples and humidity sensors upstream of the TGA chamber (see section S6).

The morphology and elemental distribution of all MOF and MOF/G samples were examined by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (FEI Quanta 3D scanning electron microscope, 10-kV accelerating voltage). Water samples were examined using nuclear magnetic resonance (NMR) spectroscopy (Bruker DRX-500) and inductively coupled plasma atomic emission spectroscopy (Optima 7000 DV, PerkinElmer).

The thermal response of all materials was measured using a homemade setup (S7) consisting of an insulation cell made of extruded polystyrene foam with a fast-response T-type thermocouple (Neoflon PFA, American Wire Gauge 40, OMEGA Engineering) installed at the bottom of the cell. An incandescent lamp (150 W) was placed 60 cm above the cell to ensure the flux of 1000 ± 30 W m−2, and the cell temperature was equilibrated with the surroundings before flux exposure (25° ± 0.5°C).

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