S1

Supporting information

Double Solvent Sensing Method for Improving Sensitivity

and Accuracy of Hg(II) Detection Based on Different Signal

Transduction of a Tetrazine Functionalized Pillared MOF

Sayed Ali Akbar Razavi†, Mohammad Yaser Masoomi†, Ali Morsali*

Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14117-

13116, Tehran, Islamic Republic of Iran

∗E-mail: morsali_a@modares.ac.ir.Tel: (+98) 21-82884416

†These authors contributed equally to this work.

S2

1. Synthesis of pillar spacer.

Scheme S1. Synthesis of DPT.

S3

2. Characterization of TMU-34(-2H)

Figure S1. PXRD pattern of TMU-34(-2H) is various conditions.

S4

Figure S2. Representation of a single 2D layer constructed from the coordination of oba ligands

around the paddlewheel coordinated Zn centers along (1, 0, 0) direction. Color code: O: red; C:

grey; and Zn: bright-blue. Hydrogen atoms are eliminated for clarity.

Figure S3. Representation of TMU-34(-2H) along the crystallographic axes.(a) a axis, (b) b axis,

(c) c axis. Color code: O: red; N: blue; C: grey; and Zn: pink. Hydrogen atoms are eliminated for

clarity.

S5

Figure S4. N2 adsorption/desorption of TMU-34(-2H) at 77 K.

Figure S5. TGA curve of TMU-34(-2H).

S6

3. EDAX analysis.

Figure S6. EDAX analysis of TMU-34(-2H) in water (before sensing).

Figure S7. EDAX analysis of Hg(II)@TMU-34(-2H) in water (after sensing). As it is clear,

moreover than Zn, Hg(II) is appeared which reveal that TMU-34(-2H) sense and adsorbed

Hg(II).

S7

Figure S8. EDAX analysis of TMU-34(-2H) in acetonitrile.

Figure S9. EDAX analysis of Hg(II)@TMU-34(-2H) in acetonitrile. As it is clear, moreover

than Zn, Hg(II) is appeared which reveal that TMU-34(-2H) sense and adsorbed Hg(II).

S8

For calculating the wt% of Zn (as member of TMU-34(-2H) clusters) and adsorbed Hg(II), we

assume that, every tetrazine group inside the TMU-34(-2H) framework interact with one Hg(II)

ion. On other hand, there is two Zn inside the framework for one tetrazine functionalized DPT

spacer (TMU-34(-2H):

[Zn(OBA)(DPT)0.5].DMF

1 mol DPT ≡ 2 mol Zn

1mol DPT ≡ 1 mol Hg(II)

So, it is rational to say that there is one Hg(II) adsorbed after sensing For two Zn inside the

framework.

1 mol Hg(II) ≡ 2 mol Zn

By considering this assumption, and if all tetrazine moiety interact with Hg(II) ions, wt% of

Hg(II) adsorbed after sensing is equal to:

��%����� = �����1 ����� �����1 ����� + �����2 ���� × 100 = 1 × 200.6

1 × 200.6 + 2 × 65.4× 100 = 61%

So, after complete interaction of 1 mol Hg(II) by 1 mol tetrazine (DPT pillar spacer), wt% of

Hg(II) is equal to 61%.

Emulsion of 2mg TMU-34(-2H) in 1 ml water and acetonitrile exposed to 1 ml stock solution of

10-3

M Hg(II) separately after 10 min sonication. Calculated wt% for Hg(II)@TMU-34(-2H)

based on EDAX analysis is 62% and 72% in water and acetonitrile, respectively. Here, wt% of

Hg(II) in water is completely matched with calculated wt% of Hg(II), but wt% of Hg(II) in

acetonitrile is slightly higher which is related to the higher concentration of solution of Hg(II)

and caused to more Hg(II) adsorption.

Concentration of Hg(II) in PL procedure (10-3

M stock solution of Hg(II)):

������������� = 1 ��������� !���"����� × 10#$MolarityofHgII�instocksolution�1 ��������� !���"����� + 4 ���6�734−2�������:;��� = 1 × 10#$

1 + 4� = 2 × 10#<

Concentration of Hg(II) in EDAX analysis (10-3

M stock solution of Hg(II)):

������������� = 1 ��������� !���"����� × 10#$MolarityofHgII�instocksolution�1 ��������� !���"����� + 1 ���6�734−2�������:;��� = 1 × 10#$

1 + 1� = 10 × 10#<

It is necessary to mention that, we used higher concentration of Hg(II) in EDAX analysis for

demonstrating our assumption that one tetrazine group inside the framework interact with one

Hg(II) ion which emulsion of TMU-34(-2H) in water show it very clearly.

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4. Mapping of Hg and Zn.

Figure S10. Zn-Map image of TMU-34(-2H) in water. Color: Zn: green.

Figure S11. Zn and Hg(II)-Map image of Hg(II)@TMU-34(-2H) in water. Color: Zn: green;

Hg(II): red.

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Figure S12. Zn-Map image of TMU-34(-2H) in acetonitrile. Color: Zn: green.

Figure S13. Zn and Hg(II)-Map image of Hg(II)@TMU-34(-2H) in water. Color: Zn: green;

Hg(II): red.

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5. TMU-34(-2H) PL behavior in different solvents.

Table S1. Reichard’s solvent polarity (=>?)1 and TMU-34(-2H) intensity in related solvent.[2]

Solvent =>? Intensity

(a.u.)

Methanol 0.762 115.4

Ethanol 0.654 107.6

Acetonitrile 0.460 99.4

DMF 0.386 86.0

Toluene 0.099 59.2

n-Hexane 0.009 35.7

Figure S14. Linear relationship between Reichard’s solvent polarity (=>?) and TMU-34(-2H)

intensity in related solvent.

S12

6. PL of all cations in acetonitrile and water.

Figure S15. PL of all cations in acetonitrile.

Figure S16. PL of all cations in water.

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Figure S17. The effects of Hg(II) Molarity on TMU-34(-2H) emission peak, (a) Acetonitrile. (b)

water.

Figure S18. Selectivity toward Hg(II) in presence of other cations. (a) in acetonitrile. (b) in

water.

Figure S19. Stern-Volmmer curve for Hg(II). (a) in acetonitrile. (b) in water.

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7. Calculation of detection limit (DL).

The International Union of Pure and Applied Chemistry (IUPAC) defines the detection limit as

the smallest concentration or absolute amount of analyte that has a signal significantly larger

than the signal arising from a reagent blank or noises.

One common approach to formulating the detection limit (DL) is based on equation 1:2

@A = B.CDE (1)

Here, k is confidence factor, m is calibration sensitivity and sb is standard deviation of the

blanks. Based on IUPAC criteria, here k is equal to 3. This is equivalent to defining the LOD as

that concentration at which the S/N ratio equal to 3 at 99% or k value of 3 corresponds to a

98.3% confidence level. To measure sb, a suitable number (8–10 replicates is common) of an

appropriate blank must be replicated to determine the standard deviation of the blank signal. The

blank measures only the background or baseline noise. Standard deviation of the blank signal is

calculated by equation 2:2

�F = G∑ IJ#IK�LMNJOM?#P (2)

In this equation, Ii is the intensity of blank number I, Ia is average intensity of all replicates and N

is the number of replicates. The calibration sensitivity, m, is the slope of the calibration curve. In

calibration curve, signal versus of concentration of analyte is figured and the slope of linear

curve is equal to m.2

In this work, based on IUPAC criteria, we set k at 3, and calculated parameters for TMU-34(-

2H) is both water and acetonitrile are represented is table S2.

Table S2. Parameters for TMU-34(-2H) is water and acetonitrile for DL calculation.

Solvent k sb N m (M-1) Detection Limit (M)

Acetonitrile 3 0.82 10 359362 6.9 ×10-6

Water 3 0.61 10 106 1.8 ×10

-6

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8. Calculation of sensitivity factor (S)

In MOF-based sensors, the word “sensitivity” has occasionally been confused with “response”.

Sensitivity factor (S) is defined as changes of response in the presence of analyte over initial

response (equation 4):

Q = RS#RJRJ

(4)

which Ri and Rf are initial response of the sensor and the response of the sensor in the presence

of the desired cations. Also, response is defined as proportion of intensity of TMU-34(-2H) PL

emission peak in water and acetonitrile .

Table S3. Sensing factors for all cations.

Cation Ri Rf S

Hg(II) 0.167 7.017 41.02

Cu(II) 0.167 0.430 1.57

Al(III) 0.167 0.413 1.47

Na(I) 0.167 0.154 0

Mg(II) 0.167 0.172 0.03

Sr(II) 0.167 0.130 0.03

Co(II) 0.167 0.174 0.04

Ni(II) 0.167 0.194 0.17

Zn(II) 0.167 0.249 0.50

Cd(II) 0.167 0.127 0

Pb(II) 0.167 0.327 0.96

Li(I) 0.167 0.152 0

K(I) 0.167 0.156 0

Cr(III) 0.167 0.224 0.34

Fe(II) 0.167 0.175 0.05

Fe(III) 0.167 0.188 0.13

Ca(II) 0.167 0.172 0.03

It is obvious that there is very significant and noticeable difference between Hg2+

sensing factor

and other cations. So, Sensitivity of 2D sensing curve toward Hg2+

is highly improved.

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Table S4. TMU-34(-2H) sensing parameter in water and acetonitrile and comparison with other

MOF based Hg2+

sensors.

Sensor Response

Time

KSV(M-1) Detection

Limit(M)

Sensing

Method

Reference

TMU-34(-2H) in Acetonitrile 15second 63618 6.9×10-6

Quenching This Work

TMU-34(-2H) in Water 15 second 3737 1.8×10-6

Enhancement This Work

[Zn(2-NH2bdc)(bibp)]n 24 hour 4550 4.2×10−8

Quenching 3

[Eu2(bqdc)3(H2O)(DMF)3].0.5DMF

.H2O 24 hour ---- 1×10

-8 Quenching

4

[TbL1.5(H2O)2]·H2O 2 day 7465 --- Quenching 5

Uio-66 based sensor 10 second ---- 5.2×10−8

UV-Visible 6

2,9-DMP 20 second ---- 4×10−8

Quenching 7

LMOF-263 5 min 459,446 1.8×10−11

Quenching 8

PCN-224 2 min. 6.4×105 6×10

−9 Quenching

9

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9. Reusability in acetonitrile and water.

Figure S20. PL intensity of TMU-34(-2H) in different cycles for reusability application in

acetonitrile.

Figure S21. PL intensity of TMU-34(-2H) in different cycles for reusability application in water.

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Figure S22. PXRD pattern of TMU-34(-2H) after 5 cycles fluorescence measurement

.

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