Composite MOF foams: the example of UiO-66/polyurethane

Moisés L. Pinto,*a,b Sandra Dias,

a João Pires,

a

a Department of Chemistry and Biochemistry, and CQB, Faculty of Sciences, University of Lisbon, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal. Fax: +351 217500088; Tel:+351 217500898 b Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal. E-mail: moises.pinto@fc.ul.pt

Characterization

Nitrogen adsorption isotherms, at -196 ºC, were obtained in an automatic apparatus

(ASAP 2010; Micromeritics). Before the adsorption experiments, the samples were outgassed

under vacuum better than 10-2 Pa for 2.5 h at 120 ºC. This relatively low temperature was used

to prevent polyurethane decomposition. The adsorption isotherms were analyzed by the

Brunauer–Emmett–Teller (BET) equation, for the estimation of the specific surface area (ABET),

and by the t-plot method using the Harkins–Jura equation, for the estimation of the microporous

volume.

The n-hexane and benzene adsorption isotherms, at 25 ºC, were obtained by the

gravimetric method in a balance suited for vacuum (Disbal, C.I. Electronics). Samples of about

50 mg were outgassed with a heating program of 2 ºC min-1 from room temperature to 120 ºC

and kept at this temperature for 2.5 h, under a final vacuum better than 10-2 Pa. The vapor was

then introduced in the system, and allowed to equilibrate with the sample. Pressure readings

were made with a capacitance transducer (CMR 262, Pfeiffer Vacuum). The temperature was

controlled using a water bath (GD120, Grant), with 0.05 ºC precision. The vapors were purified

in situ by freeze–vacuum–thaw cycles. The weighting scale was connected to a computer and

the weight was recorded by software (Labweigh; C.I. Electronics) at constant time intervals. In

some cases, several hours were necessary until equilibrium was attained (constant weight). The

adsorbed amounts were converted to liquid volume using the respective molar volume at 25 ºC.

TG-DSC experiments were performed in an apparatus (Setaram, TG-DSC 111) between

30 and 600 ºC. The experiments had a precision of 0.001 mg and 0.05 mW. Samples of about

15 mg in steel crucibles were used, with a heating rate of 1 ºC min-1, in air (Air Liquid, 20% vol.

oxygen in nitrogen) with a flux of 0.5 cm3 s

-1 measured with a glass fluxmeter (Brooks

Instruments N.V., tube size R-2-15-AA).

SEM micrographs were obtained in a Jeol JSM-5200 LV equipment, after been gold

plated.

Powder XRD data was obtained in a Philips Analytical PW 3050/60 X’Pert Pro,

equiped with a X’Celerator detector.

Results

DRIFT

Figure S1 – DRIFT spectra of the UiO-66 and composite 3, after several cleaning steps: a) as

synthesised material, b) after soxhlet extraction with dichloromethane and c), d) and e) after

successive cycles of heating at 150ºC under vacuum for 4 hours.

9001100130015001700

Ab

sorv

an

ce /

au

wave number (cm-1)

UiO-66a

b

c

d

e

9001100130015001700

Ab

sorb

an

ce /

au

wave number (cm-1)

Composite 3a

b

c

d

e

DRX

Figure S2 – Powder XRD of the UiO-66 and UiO-66 after the activation procedure.

5 15 25 35 45

a.u

.

2 Θ

UiO-66 activated

UiO-66

TG-DSC

To estimate the content of UiO-66 on the composites A and B, the mass of sample at 150 ºC

was considered as the dry mass for all the samples. As can be seen in Figure S1, this

corresponds to a point after the initial mass loss due to the dehydration of the materials. The

mass difference between the mass at 150 ºC and at 550 ºC is considered as the mass loss due to

the decomposition of the materials and the formation of ZrO2, since after 550 ºC the mass

becomes constant for all cases (Figure S1). For the case of UiO-66 a theoretical mass of 43.5%

should be obtained at the end, assuming the decomposition of the BDC linkers. Experimentally,

at 550 ºC we have obtained 40% of the initial mass at 150 ºC and this value supports the

assumption made for the complete decomposition of the UiO-66 to ZrO2. For the composites, at

550 ºC we have obtained 28% and 25% of the initial mass at 150 ºC, which we assume that is

ZrO2 formed from the decomposition of the UiO-66 since at 550 ºC the polyurethane is

completely decomposed in air. Comparing the content of ZrO2 formed from the composites with

that formed from pure UiO-66, we can estimate a content of 71% and 64% of UiO-66 for the

composite A and B.

Powder XRD of the UiO-66 and composite 3 calcined in air (Figure S4) shows is that in both

cases the same solid is obtained at the end of the calcinations and TG-DSC experiments. The

powder pattern is compatible with ZrO2, mainly in the cubic phase (ICDD PDF# 27-997) with

some minor part in the monoclinic phase (ICDD PDF# 36-420). This supports the estimation of

the UiO-66 content on the composite materials presented above, based on the mass remaining at

the end of the TG-DSC experiments.

Figure S3 – TG-DSC of the pure UiO-66, pure PUF, and composites A and B, in air.

-20

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Heat flow / mW

mass loss %

Temperature / ºC

UiO-66

mass loss

heat f low

Exo.

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Heat flow / mW

mass loss %

Temperature / ºC

PUF

mass loss

DTG

Exo.

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Heat flow / mW

mass loss %

Temperature / ºC

Composite A

mass loss

heat f low

Exo.

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25

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Heat flow / mW

mass loss %

Temperature / ºC

Composite B

mass loss

heat f low

Exo.

Figure S4 – Powder XRD of the white powder obtained after calcinations of UiO-66 and

composite A under air. Diffraction data for cubic and monoclinic ZrO2 is indicated.

5 15 25 35 45

a.u

.

2 Θ

calcined composite A

calcined UiO-66

*

*

* cubic phase

† monoclinic phase

†† † †