Supporting Information for

Structure-Property Relationship in Energetic Cationic Metal–

Organic Frameworks: New Insight for Design of Advanced

Energetic Materials

Yao Du,† Hui Su,† Teng Fei,† Baoping Hu,† Jichuan Zhang,† Shenghua Li,*,† Siping Pang,*,† and

Fude Nie‡

†School of Materials Science & Engineering, Beijing Institute of Technology, Beijing 100081, P. R.

China ‡Institute of Chemical Materials, China Academy of Engineering Physics (CAEP), Mianyang,

Sichuan 621900, P. R. China

E-mail: lishenghua@bit. edu.cn; pangsp@bit.edu.cn

Content

1. The comparison between ligands btrz and atrz and the synthesis routes to the target CMOFs in

this paper

2. Crystal data and structure refinement details for the title complexes

3. The phase purities of eight btrz and atrz-based 3D CMOF

4. The stabilities of eight btrz and atrz-based 3D CMOFs

5. Calculation of enthalpies of formation for ligand btrz and eight energetic CMOFs

6. Calculation of detonation properties of eight energetic CMOFs

7. Crystal structures for eight energetic CMOFs in this paper

8. IR characterization for the target CMOFs

Caution! Although none of the complexes described herein have exploded or detonated in

the course of this research, these materials should be handled with extreme care using the

best safety practices.

1. The properties comparison between ligand btrz and atrz and the synthesis routes to the

target CMOFs in this paper.

In general, the azo linkage not only can enhance the decomposition temperatures and densities but

also dramatically increases the heats of formation (HOFs) for small organic compounds, and the

comparison results between btrz and atrz were listed in Scheme S1.

Scheme S1. The effect of azo group on btrz and atrz

The synthesis routes to eight CMOFs in this study were shown in Scheme S2 and Scheme

S3.

N

N

N N

N

N

btrz

M(ClO4)2

Water

N

N

N N

N

N

M

M[M(btrz)3](ClO4)2

N

N

N N N

N

N

N

atrz

M(ClO4)2

Water

N

N

N N N

N

N

N

M

M[M(atrz)3](ClO4)2

M=Cu, Fe, Zn

3

3

Scheme S2. Synthesis, coordination modes, and formulae for btrz and atrz based 3D CMOFs with perchlorate

anions as counter ions

N

N

N N

N

N

M

M[M(btrz)3](NF)2

M = Cu, Zn; KNF is potassium nitroformate

N

N

N N

N

N

M

M

ClO4

anion exchange

KNF aqueous solution

[M(btrz)3](ClO4)2

C(NO2)3

Scheme S3. Synthesis, coordination mode, and formulae for btrz based 3D CMOFs with nitroformate anions as

counter ions

2. Crystal data and structure refinement details for the title complexes

Complexes (atrz-Cu)·2H2O, btrz-Zn, Cu-NF and Zn-NF were synthesized and

characterized by X-ray single crystal diffraction for the first time, and the crystal data and structure

refinement details for all CMOFs in this study were listed in Table S1 and S2.

Table S1. Crystal data and structure refinement details for btrz-based complexes

Compound name btrz-Cu btrz-Fe btrz-Zn Cu-NF Zn-NF

CCDC no. 6642591 1370372 1570227 1571482 1571481

Formula C12H12Cl2CuN18O8 C12H12Cl2O8FeN18 C12H12Cl2ZnN18O8 C14H12CuN24O12 C14H12ZnN24O12

T /K 293 (2) 190 172(2) 173(2) 173(2)

M 670.84 663.09 672.67 772.02 773.85

Crystal system Trigonal Trigonal Trigonal Trigonal Trigonal

Space group, Z R3—

c, 6 R3—

, 6 R3—

, 6 R3—

c, 6 R3—

c, 6

a /Å 10.9709(11) 10.9379(8) 10.9003(5) 12.5362(7) 12.6199(8)

b /Å 10.9709(11) 10.9379(8) 10.9003(5) 12.5362(7) 12.6199(8)

c /Å 35.314(6) 34.555(3) 35.593(4) 31.473(5) 31.550(3)

α /° 90 90 90 90 90

β /° 90 90 90 90 90

γ /° 120 120 120 120 120

V / Å3 3681.0(8) 3580.2(4) 3662.5(5) 4283.5(7) 4351.6(6)

µ(Mo-Kα) / mm-1 1.189 0.935 1.306 0.870 0.950

Dcalc/g·cm-3 1.816 1.85 1.830 1.796 1.772

2θmax /° 50.0 48.2 61.0 50.6 46.2

Measd/ Unique

reflns 6098/729 1280/997 4161/1485 6066/868 4688/890

Rint 0.0217 0.06 0.0537 0.0632 0.0728

Parameters

refined 83 156 163 93 106

R1, wR2 [I >

2σ(I)] 0.0571, 0.1614 0.0382, 0.0418 0.0384, 0.0810 0.0443, 0.1179 0.0372, 0.0830

R1, wR2 (all data) 0.0606, 0.1657 - 0.0742, 0.0924 0.0683, 0.1330 0.0624, 0.0931

Max, min peak

/e·Å–3 0.616, -0.979 4.85, -2.50 0.409, -0.357 0.524, -0.423 0.356, -0.359

Table S2. Crystal data and structure refinement details for atrz-based complexes

Compound name (atrz-Cu)·2H2O (atrz-Fe)·2H2O (atrz-Zn)·H2O

CCDC no. 1570245 8557373 15626364

Formula C12H16Cl2CuN24O10 C12H16Cl2FeN24O10 C12H14Cl2ZnN24O9

T /K 173(2) 295(2) 293(2)

M 790.93 783.24 774.74

Crystal system Monoclinic Monoclinic Monoclinic

Space group, Z P21/c, 2 P21/c, 2 P21/c, 2

a /Å 8.2990(6) 8.1901(3) 8.1860(16)

b /Å 20.2363(11) 20.1869(7) 20.160(4)

c /Å 8.6572(5) 8.9629(3) 8.9521(18)

α /° 90 90 90

β /° 92.740(2) 90.8456(16) 91.04(3)

γ /° 90 90 90

V / Å3 1452.24(16) 1481.70(9) 1477.1(5)

µ(Mo-Kα) / mm-1 1.030 0.781 1.100

Dcalc/g·cm-3 1.809 1.756 1.742

2θmax /° 50.7 50.0 52.7

Measd/ Unique reflns 9036/2643 12436/2614 15068/3007

Rint 0.0863 0.0710 0.0351

Parameters refined 229 223 223

R1, wR2 [I > 2σ(I)] 0.0499, 0.0952 0.0843, 0.2613 0.0436, 0.1200

R1, wR2 (all data) 0.0968, 0.1114 0.1145, 0.2798 0.0509, 0.1250

Max, min peak /e·Å–3 0.598, -0.517 0.704, -0.740 0.599, -0.705

3. The phase purities of eight btrz and atrz-based 3D CMOFs

The phase purities of six btrz and atrz-based 3D CMOFs with ClO4¯ as counter anions were

verified by powder X-ray diffraction (PXRD) studies, which indicates that the diffraction patterns of the

fresh samples are consistent with the calculated ones (Figure. S1).

Figure S1. Powder X-ray diffraction patterns of six 3D CMOFs: btrz-Cu (a), btrz-Fe (b), btrz-Zn (c), atrz-Cu

(d), atrz-Fe (e), atrz-Zn (f).

Similarly, the phase purities of Cu-NF and Zn-NF were also verified by powder X-ray diffraction

(PXRD) studies, which indicates that the diffraction patterns of the fresh samples are consistent with the

calculated ones (Figure. S2).

Figure S2. Powder X-ray diffraction patterns of Cu-NF (a) and Zn-NF (b).

4. The stabilities of eight btrz and atrz-based 3D CMOFs

Chemical stabilities

The chemical stabilities for btrz-Zn and atrz-Zn in HCl/NaOH aqueous solutions with pH

values ranging from 1 to 14 for 24 h were studied, and the results were shown in Figure S3. The

PXRD patterns showed that btrz-Zn and atrz-Zn can keep its crystallinity in different pH values

ranging from 1 to 10. However, in pH=14 condition, the framework for atrz-Zn collapsed. The

peak at about 7 degrees for btrz-Zn samples at different pH is consistent with its simulated pattern,

which is too weak to display.

Figure S3. PXRD patterns of as-prepared atrz-Zn in various HCl/NaOH aqueous solutions with different pH

values for 24 hours (a). PXRD patterns of as-prepared btrz-Zn in various HCl/NaOH aqueous solutions with

different pH values for 24 hours (b).

Thermal stabilities

A TG-DSC method was carried out using a linear heating rate of 10 °C min−1 in a nitrogen

atmosphere to evaluate the thermal behavior of the eight target compounds, and the DSC-TG

curves were shown in Figure S4-S7. Although all data for them were obtained, the TG curve of

atrz-Fe is very special, as an explosion took place in its testing process and thus a rapid

weight-loss occurred (Figure S5b).

Figure S4. DSC-TG curves for btrz-Cu (a), atrz-Cu (b) and atrz (c).

Figure S5. DSC-TG curves for btrz-Fe (a) and atrz-Fe (b).

Figure S6. DSC-TG curves for btrz-Zn (a) and atrz-Zn (b).

Figure S7. DSC-TG curves for Cu-NF (a) and Zn-NF (b).

The coordination bond lengths and hydrogen bonds for six energetic CMOFs with

perchlorate anions as counter ions

The coordination bond lengths and hydrogen bond lengths for six energetic CMOFs were

listed in Table S3 and S4, respectively.

Table S3. Coordination bond lengths /Å for six complexes

Compound atrz-Cu btrz-Cu atrz-Fe btrz-Fe atrz-Zn btrz-Zn

M-N bond lengths 2.011(3) 2.173(6) 2.007(3) 2.158(2) 2.145(3)

M-N bond lengths 2.022(3) 2.184(6) 2.151(3) 2.169(2) 2.153(3)

M-N bond lengths 2.400(3) 2.107(4) 2.187(6)

Table S4. Hydrogen bond lengths /Å and bond angles /°in six complexes.

Compound D–H···A d(D–H) d(H···A) d(D···A) <D–H···A

atrz-Cu

C2–H2···O1 0.9500 2.5443(41) 3.1753(59) 124.027

C3–H3···O3 0.9500 2.7258(44) 3.0338(62) 99.679

C3–H3···O2 0.9500 2.4281(34) 3.3003(54) 152.473

btrz-Cu C1–H1···O2 0.93 2.57 3.45(2) 157

atrz-Fe C4–H4A···O1 0.930 2.3403(85) 3.2593(117) 169.705

C4–H4A···O2 0.930 2.7168(108) 3.3280(134) 124.069

btrz-Fe C13–H13···O6 0.891 2.6107 3.4697 162.306

C6–H6···O8 0.939 2.6671 3.5988 171.572

atrz-Zn

C1–H1···O1 0.930 2.3783(104) 3.2839(107) 164.528

C1–H1···O1’ 0.930 2.2770(161) 3.2053(163) 174.61

C1–H1···O2 0.930 2.7444(98) 3.3756(102) 125.944

C1–H1···O2’ 0.930 2.6979(182) 3.2878(104) 122.164

btrz-Zn

C1–H1···O2 0.950 2.3959(136) 3.3241(137) 165.482

C4–H4···O4 0.950 2.4465(151) 3.3806(161) 167.614

C3–H3···O6 0.951 2.6333(139) 3.1594(320) 115.318

5. Calculation of enthalpies of formation for ligand btrz and eight energetic CMOFs

Isodesmic reaction, in which numbers of electron pairs and chemical bond types are

conserved, has been employed very successfully to give heat of formation5. Based on the

optimized structure for btrz, the total energy (E0) and thermodynamic parameters, including zero

point energy (ZPE) and thermal correction to enthalpy (HT), were obtained at the

B3LYP/6−311G++(d,p) level. For the isodesmic reaction (Scheme S4), gas-phase heat of reaction

(∆H298K) can be calculated from the following Equation (1):

∆H298K =∑∆Hf,P(gas,298K)–∑∆Hf,R(gas,298K) (1)

where H f, R and H f ,P are the gas−phase heats of formation for reactants and products at 298 K,

respectively.

Meanwhile, ∆H298 K can also be calculated using the following Equation (2):

∆H298 K = ∆E298 K + ∆(PV) = ∆E0 + ∆ZPE + ∆HT+ ∆(nRT) (2)

Where ∆E0 is the change in total energy between the products and the reactants at 0 K; ∆ZPE

is the difference between the zero-point energies of the products and the reactants; ∆HT is thermal

correction from 0 K to 298.15 K. Since there is no change in number of total molecules, ∆(PV) =

∆(nRT) =0. Therefore, the heat of formation in gas-phase can be figured out according to ∆H298 K

and gas-phase heats of formation of other reactants and products. The gas-phase heats of formation

for 4-amino-1,2,4-triazole and hydrazine were acquired by G2 method and from the literature,

respectively.

Scheme S4. Isodesmic reactions

Table S5. Calculated total energy (E0), zero−point energy (ZPE), thermal correction (HT), and enthalpy of

formation (HOFGas) of compounds btrz and reference compounds.

Compd. E0/a.u. ZPE (kJ/mol) HT (kJ/mol) HOFGas (kJ/mol)

4-amino-1,2,4-triazole -297.6224679 192.51 14.03 336.87

hydrazine -111.910687 139.88 11.04 50.636

btrz -483.359561 254.37 21.36 581.83

For assessment of the potential performance of the energetic material of interest, however, the

desired quantity is usually the condensed phase ∆Hf. Condensed phase heats of formation can be

determined using the gas-phase heats of formation and heat of phase transition (either sublimation

or vaporization) according to Hess’ law of constant heat summation. For compound btrz, it is solid

at room temperature and its solid heat of formation can be calculated by equation

∆H(Solid)=∆H(Gas)−∆H(Sublimation). The heat of sublimation was calculated based on Trouton's

rule7 by using the equation ∆Hsub= 0.188 ×Td. Therefore, the solid heat of formation for btrz

=581.83-268 × 0.188 = 531.45 kJ/mol.

The constant-volume combustion energies (∆cU) for eight CMOFs were measured by an oxygen

bomb calorimeter. The enthalpy of formation (∆fH°) was calculated from ∆cU and a correction for

change in gas volume during combustion was included (Scheme S5, eq 1). The standard enthalpies of

formation (∆fH°) of these energetic MOFs were back calculated from the heats of combustion on the

basis of combustion equation (Scheme S5, eqs 2-6), Hess’s Law as applied in thermochemical

equations (Shceme S5, eqs 7-11), and the known standard heats of formation for metal oxide,

hydrogen chloride, water and carbon dioxide (Table S6). M represents Cu and Zn, and the calculated

∆fH° was listed in Table S7.

Scheme S5. Combustion reactions and Hess’s Law for the combustion reactions of eight energetic MOFs

Table S6 Standard heats of formation for the combustion products and possible detonation products

Compound Standard

heats of formation Compound

Standard heats

of formation Compound

Standard heats

of formation

H2O (l) -285.8 kJ/mol Fe2O3 -822.1 kJ/mol FeCl3 -399.5 kJ/mol

H2O (g) -241.8 kJ/mol CuO -155.2 kJ/mol FeCl2 -341.8 kJ/mol

CO2 (g) -393.5 kJ/mol ZnO -350.5 kJ/mol HCl (g) -92.311 kJ/mol

Fe3O4 -1118.4 kJ/mol ZnCl2 -415.1 kJ/mol

FeO -272.0 kJ/mol CuCl2 -220.1 kJ/mol

6. Calculation of detonation properties of eight energetic CMOFs

The heat of detonation (Q) was calculated through Hess’ Law and detonation reactions using

the calculated heat of formation. According to the largest exothermic principle proposed by

Kamlet, the detonation reactions of our synthesized energetic MOFs were proposed in Scheme S6,

and their heats of detonation were evaluated by the empirical Kamlet formula (Scheme S7, eq 1).

With the data for molecular weight, density, and heat of formation in hand, the detonation

pressures (P) and velocities (VD) of eight complexes could be calculated. We adopted two different

methods for the calculation of detonation properties of eight MOFs with general formula

{[ML3]A2}n. (M=Cu, Fe, Zn; L=btrz, atrz; A=ClO4-, C(NO2)3

-). These methods are shown as

follows: (i) the commercial program EXPLO5 v6.01; (ii) our recently developed method on the

basis of the empirical Kamlet formula, and the results were given in Table S7.

(i) Adopting our developed method for the calculation of detonation properties of various

energetic MOFs

According to the largest exothermic principle and considering the standard heats of formation

for the possible detonation products in Table S6, the detonation reactions of our as-synthesized

energetic MOFs were proposed in Scheme S6. M represents Cu, Fe, and Zn.

Scheme S6. Detonation reactions of eight energetic MOFs

Based on the detonation reactions of energetic CMOFs, the detonation properties for these

CMOFs were evaluated by the empirical Kamlet formula, as shown in Scheme S7. In the Kamlet

equations, VD represents detonation velocity (km s-1) and P is detonation pressure (GPa), ρ is the

density of explosive (from gas pycnometer, g cm-3). N is the moles of detonation gases per gram of

explosive, M is the average molecular weight of these gases and Q is the heat of detonation (kcal

kg-1). ∆fH(explosive) is the experiment determined (back-calculated from -∆cU) enthalpy of

formation of energetic MOF.

Scheme S7. The Kamlet formula

(ii) Adopting EXPLO5 v6.01 for the calculation of detonation properties of various energetic

MOFs

To confirm the prediction accuracy of our developed method, we also employed EXPLO5

v6.01 to calculate the detonation properties of these MOFs. Using the molecular formula, density

(from gas pycnometer), and experiment determined (back-calculated from -∆cU) enthalpy of

formation (∆fHo), we can use the EXPLO5 computer code in its new version 6.01 to calculate the

detonation velocity (VD), detonation pressure (P), and heat of detonation (Q), as illustrated in

Table S7.

Table S7. The measured values of constant-volume combustion energies and the calculated energetic properties

for eight energetic MOFs.

Comp. OB[a]

-∆cU[b]

-∆fH[c]

∆fH°[d]

VD[e]

P[f]

Q[g]

btrz-Cu -23.85 11580.9 7739 1248 6945[h]

(7316) [i] 21.50[h] (22.69) [i]

4997[h]

btrz-Fe -21.20 12309.7 8132 1424 7130[h] (7291) [i]

22.58[h] (22.77) [i]

5504[h]

btrz-Zn -25.33 11646.9 7805 1119 6911[h] 21.15[h] 5080[h]

atrz-Cu -22.49 11116.4 8354 1668 6949[h] (7265) [i]

20.95[h] (21.52) [i]

5006[h]

atrz-Fe -23.79 11225.7 8349 1640 6820[h] (7052) [i]

19.90[h] (20.28) [i]

5185[h]

atrz-Zn -21.15 11104.0 8365 1679 6944[h] 20.70[h] 5266[h]

Cu-NF -18.65 11458.9 8811 1432 7420[h] 23.78[h] 5330[h]

Zn-NF -18.61 11567.4 8916 1341 7401[h] 23.64[h] 5397[h]

MOF-Cu -15.64 11557.8 8244 1651 6780[h] 19.15[h] 4562

[a] Oxygen balance based on CO. [b] Experimental determined (oxygen bomb calorimetry) contant volume energy of combustion (kJ kg-1). [c] Expremental molar enthalpy of combustion (kJ mol-1). [d] Experiment determined (back-calculated from -∆cU) enthalpy of formation (kJ mol-1). [e] Detonation velocity (m s-1). [f] Detonation pressure (GPa). [g] Heat of detonation (kJ kg-1). [h]The detonation properties were calculated by our developed method. [i] The detonation properties were calculated by EXPLO5 v6.01. btrz-Cu: {[Cu(btrz)3](ClO4)2}n, CuC12H12Cl2N18O8, M=671; btrz-Fe: {[Fe(btrz)3](ClO4)2}n, FeC12H12Cl2N18O8, M=663; btrz-Zn: {[Zn(btrz)3](ClO4)2}n, ZnC12H12Cl2N18O8, M=673; atrz-Cu: {[Cu(atrz)3](ClO4)2}n, CuC12H12Cl2N24O8, M=755; atrz-Fe: {[Fe(atrz)3](ClO4)2}n, FeC12H12Cl2N24O8, M=772; btrz-Zn: {[Zn(btrz)3](ClO4)2}n, ZnC12H12Cl2N24O8, M=757; Cu-NF: {[Cu(btrz)3](C(NO2)3)2}n, CuC14H12N24O12, M=772; Zn-NF: {[Zn(btrz)3](C(NO2)3)2}n, ZnC14H12N24O12, M=774; MOF(Cu): {[Cu(atrz)3](NO3)2}n, CuC12H12N26O6, M=680.

7. Crystal structures for eight energetic CMOFs in this paper

The coordination environment and 3D structures of atrz-Cu, atrz-Zn, btrz-Cu, and btrz-Zn were shown

in Figure S8-S11, and the coordination environment and 3D structures for Cu-NF and Zn-NF were shown in

Figure S12-S13.

Figure S8. Coordination environment of Cu in atrz-Cu (a). 3D structure of atrz-Cu, the water molecules and

perchlorate anions were in the cavities (b).

Figure S9. Coordination environment of Fe in atrz-Fe (a). 3D structure of atrz-Fe, the water molecules and

perchlorate anions were in the cavities (b).

Figure S10. Coordination environment of Cu in btrz-Cu (a). 3D structure of btrz-Cu, the perchlorate anions

were in the cavities (b).

Figure S11 Coordination environment of Fe in btrz-Fe (a). 3D structure of btrz-Fe, the perchlorate anions were

in the cavities (b).

Figure S12. Coordination environment of Cu in Cu-NF (a). 3D framework of Cu-NF view from c-axis, the

nitroformate anions were encapsulated in the voids (b). Hydrogen atoms, and more nitroformate anions have

been omitted for clarity

Figure S13. Coordination environment of Zn in Zn-NF (a). 3D framework of Zn-NF view from c-axis, the

nitroformate anions were encapsulated in the voids (b). Hydrogen atoms, and more nitroformate anions have

been omitted for clarity

8. IR characterization for the target CMOFs

Figure S14. IR spectrum of atrz-Cu, atrz-Fe, and atrz-Zn. For atrz-Cu, IR (KBr): ν 3623, 3546, 3122, 1627,

1501, 1392, 1318, 1185, 1105, 1085, 1053, 1034, 701, 672, 623, 551, 423 cm-1; For atrz-Zn, IR (KBr): ν 3628,

3547, 3120, 1621, 1502, 1487, 1389, 1318, 1186, 1103, 1084, 1055, 1032, 989, 943, 886, 701, 670, 623, 550,

422 cm-1; For atrz-Fe, IR (KBr): ν 3626, 3546, 3120, 1624, 1502, 1389, 1318, 1186, 1102, 1084, 1055, 1032,

988, 943, 885, 702, 623, 551, 422 cm-1

Figure S15. IR spectrum of btrz-Cu, btrz-Fe, and btrz-Zn. For btrz-Cu, IR (KBr): ν 3135, 1526, 1323, 1299,

1199, 1102, 1025, 956, 937, 866, 620, 610 cm-1; For btrz-Zn, IR (KBr): ν 3130, 1528, 1514, 1353, 1326, 1297,

1203, 1101, 1015, 955, 863, 621, 608 cm-1; For btrz-Fe, IR (KBr): ν 3130, 1633, 1510, 1343, 1300, 1200, 1107,

1086, 1014, 948, 934, 869, 615 cm-1

Figure S16. IR spectrum of btrz-Zn and btrz-Zn after being immersed in KNF aqueous solution for 3 days

(left). Local IR spectrum of btrz-Zn and Zn-NF. For Zn-NF, IR (KBr): ν 3129, 1529, 1478, 1405, 1376, 1288,

1206, 1157, 1085, 1016, 991, 937, 859, 785, 734, 615 cm-1

Figure S17. Photographs show the color of btrz-Zn crystals before and after the anion exchange.

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