S1

Supplementary Information

A Modulated Hydrothermal (MHT) Approach for the Facile

Synthesis of UiO-66-Type MOFs

Zhigang Hu, Yongwu Peng, Zixi Kang, Yuhong Qian, and Dan Zhao*

Department of Chemical and Biomolecular Engineering, National University of

Singapore, 4 Engineering Drive 4, Singapore 117585.

Correspondence and requests for materials should be addressed to D.Z. (E-mail:

chezhao@nus.edu.sg).

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Calculations of isosteric heat of adsorption (Qst)

The CO2 and N2 adsorption isotherms measured at 273 K and 298 K were first

fitted to a virial equation (Equation 1). The fitting parameters were then used to

calculate the isosteric heat of adsorption (Qst) using Equation 2,

0 0

1ln ln

m ni i

i i

i i

P N a N b NT = =

= + +∑ ∑ (1)

0

mi

st i

i

Q R a N=

= − ∑ (2)

where P is pressure (mmHg), N is adsorbed quantity (mmol g-1

), T is temperature (K),

R is gas constant (8.314 J K-1

mol-1

), ai and bi are virial coefficients, m and n represent

the number of coefficients required to adequately describe the isotherms (herein, m =

5, n = 2).

Ideal Adsorption Solution Theory (IAST) Selectivity

The CO2 and N2 adsorption isotherms were first fitted to a dual-site

Langmuir-Freundlich (DSLF) model (Equation 3),

, ,

1 1

A B

A B

sat A A sat B B

A B

q b p q b pq

b p b p

α α

α α= +

+ + (3)

where q is the amount of adsorbed gas (mmol g-1

), p is the bulk gas phase pressure

(bar), qsat is the saturation amount (mmol g-1

), b is the Langmuir-Freundlich parameter

(bar-α

), α is the Langmuir-Freundlich exponent (dimensionless) for two adsorption

sites A and B indicating the presence of weak and strong adsorption sites.

IAST starts from the Raoults’ Law type of relationship between fluid and adsorbed

phase,

o

i i i iP Py P x= = (4)

01 1

1n n

ii

i i i

Px

P= =

= =∑ ∑ (5)

where Pi is partial pressure of component i (bar), P is total pressure (bar), yi and xi

represent mole fractions of component i in gas and adsorbed phase (dimensionless).

Pi0 is equilibrium vapour pressure (bar).

In IAST, Pi0 is defined by relating to spreading pressure π,

0

0

( ) (Constant)

iP i ii

i

q PSdP

RT P

π= = Π∫

(6)

where π is spreading pressure, S is specific surface area of adsorbent (m2 g

-1), R is gas

constant (8.314 J K-1

mol-1

), T is temperature (K), qi(Pi) is the single component

equilibrium obtained from isotherm (mmol g-1

).

For a dual-site Langmuir-Freundlich (DSLF) model, we have an analytical expression

for the integral,

0

, ,0 0

0

( ) (Constant) ln[1 ( ) ] ln[1 ( ) ]

iA B

Psat A sat Bi i

i A i B i

i A B

q qq PdP b P b P

P

α α

α α= Π = + + +∫

(7)

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The isotherm parameters will be known from the previous fitting. For a binary

component system the unknowns will be П, P10, and P2

0 which can be obtained by

simultaneously solving Equations 5 and 7.

The adsorbed amount for each compound in a mixture is

mix

i i Tq x q= (8)

1

1

( )

ni

oiT i i

x

q q P=

=∑ (9)

where qimix

is the adsorbed amount of component i (mmol g-1

), qT is the total adsorbed

amount (mmol g-1

).

The adsorption selectivities Sads were calculated using Equation 10.

1 2

1 2

/

/ads

q qS

p p=

(10)

In this study, IAST calculations were carried out assuming a CO2/N2 binary mixed gas

with a molar ratio of 15:85 at 298 K and pressures up to 1 bar to mimic the

composition and condition of flue gas.

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Figure S1. PXRD patterns of UiO-66-(COOH)2 synthesized under various conditions.

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Figure S2. Energy dispersive X-ray spectrometer (EDS) of UiO-66-(F)4: (a) mapping

image; (b) quantitative analysis result.

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Figure S3. FE-SEM images of UiO-66-type MOFs: (a) UiO-66 obtained from

solvothermal reactions; (b) UiO-66; (c) UiO-66-NH2; (d) UiO-66-(OH)2; (e)

UiO-66-(COOH)2; (f) UiO-66-(OCH2CH3)2; (g) UiO-66-(F)4; (h) UiO-66-(COOH)4

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Table S1. Summary of the recipe and yield for MHT synthesis of UiO-66-type MOFs.

Sample Ligand Modulator

AA (mL)

Water

(mL)

Modulator/Ligand

ratio

Yield

(%)

UiO-66 Benzene-1,4-dicarboxylic acid (BDC) 20 30 70 66

UiO-66-NH2 2-Aminoterephthalic acid (ATC) 10 40 35 72

UiO-66-(OH)2 2,5-Dihydroxyterephthalic acid (DOBDC) 30 30 105 85

UiO-66-(COOH)2 1,2,4,5-Benzenetetracarboxylic acid (BTEC) 20 30 70 90

UiO-66-(OCH2CH3)2 2,5-Diethyloxyterephthalic acid (DEOBDC) 20 30 70 95

UiO-66-(F)4 2,3,5,6-Tetrafluoro-1,4-benzenedicarboxylic acid (TFBDC) 20 30 70 90

UiO-66-(COOH)4 Benzene-1,2,3,4,5,6-hexacarboxylic acid (BHC) 30 30 105 63

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Table S2. Qst of CO2, N2 at low coverage and IAST CO2/N2 selectivity of UiO-66-type MOFs.

UiO-66 family MOFs UiO-66 UiO-66-NH2 UiO-66-(OH)2 UiO-66-(COOH)2 UiO-66-(OCH2CH3)2 UiO-66-(F)4 UiO-66-(COOH)4

Qst of CO2a) 22.19 27.42 30.10 33.63 26.20 18.66 30.47

Qst of N2a) 11.00 11.55 10.94 11.40 9.72 10.40 12.55

IAST selectivity: CO2/N2b) 17.13 24.21 34.17 35.43 24.88 15.98 25.76

a) kJ mol

-1, absolute value, b) CO2:N2 = 15:85, 298 K 1 bar.