Cu(II) Coordination Polymers Containing Mixed Ligands with Different Flexibilities: Structural Diversity and Iodine Adsorption

Reactions of N,N′-bis(3-methylpyridyl)oxalamide (L1), N,N’-bis(3-methylpyridyl)adipoamide (L2) and N,N’-bis(3-methylpyridyl)sebacoamide (L3) with tricarboxylic acids and Cu(II) salts afforded {[Cu(L1)(1,3,5-HBTC)]·H2O}n (1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid), 1, {[Cu1.5(L2)1.5(1,3,5-BTC)(H2O)2]·6.5H2O}n, 2, [Cu(L2)0.5(1,3,5-HBTB)]n (1,3,5-H3BTB = 1,3,5-tri(4-carboxyphenyl)benzene), 3, [Cu4(L3)(OH)2(1,3,5-BTC)2]n, 4, {[Cu3(L3)2(1,3,5-BTB)2]·2.5MeOH·2H2O}n, 5, and {[Cu3(L3)2(1,3,5-BTB)2 ]·DMF·2H2O}n, 6, which have been structurally characterized by using single crystal X-ray crystallography. Complexes 1–4 form a 2D layer with the {44.62}-sql topology, a 2D layer with the (4.62)2(42.62.82)-bex topology, a three-fold interpenetrated 3D net with the (412·63)-pcu topology and a 3D framework with the (410·632·83)(42·6)2(43·63) topology, respectively, whereas 5 and 6 are 3D frameworks with the (63)2(64·82)(68·85·102) topology. Complex 5 shows a better iodine adsorption factor of 290.0 mg g−1 at 60 °C for 360 min than the other ones, revealing that the flexibility of the spacer ligand governs the structural diversity and the adsorption capacity.

The -(CH 2 ) n -group of the bis-pyridyl-bis-amide (bpba) possesses suitable flexibility that may adopt the coordination environment of different metal ions, whereas the two amide groups play important roles as abundant potential hydrogen bond sites, affording CPs with remarkable topologies.On the other hand, polycarboxylate ligands that show distinct coordination modes involving chelating and bridging are also important in the organization of CPs in a mixed system [9].Benzene-1,3,5-tricarboxylic acid (1,3,5-H 3 BTC) is a planar molecule with C 3 -symmetry that may give anions of the types, BTC 3− and HBTC 2− , and intriguing structural types have been found in the bpba-based CPs supported by these anions [10].Extension of 1,3,5-H 3 BTC to the larger 1,3,5-tri(4-carboxyphenyl)benzene (1,3,5-H 3 BTB) may thus afford CPs with different structural topology.

Structure of 1
A single-crystal X-ray diffraction analysis shows that complex 1 crystallizes triclinic space group Pī.There is one Cu(II) cation, one L 1   3b, determined by using ToposPro program [11].If the dinuclear Cu(II) un defined as four connected nodes, the structure can be simplified as a four-connec with (4 4 •6 2 )-sql topology (cluster representation), Figure 3c.

Structure of 2
The crystals of complex 2 conform to the triclinic space group Pī and each asymmetric unit consists of two Cu(II) cations, one and a half L 2 ligands, one 1,3,5-BTC 3− ligand, two coordinated water molecules, and six and a half of a co-crystallized water molecules.The Cu(1) and Cu(2) metal centers are four-and five-coordinated, respectively, Figure 4a

Structure of 2
The crystals of complex 2 conform to the triclinic space group Pī and each asymmetric unit consists of two Cu(II) cations, one and a half L 2 ligands, one 1,3,5-BTC 3− ligand, two coordinated water molecules, and six and a half of a co-crystallized water molecules.The Cu(1) and Cu(2) metal centers are four-and five-coordinated, respectively, Figure 4a

Structure of 3
Complex 3 crystallizes in the monoclinic space group C2/c, and the asymmetric unit comprises one Cu(II) cation, a half of an L 2 ligand and one 1,3,5-HBTB 2− ligand.The Cu(II) cation is coordinated by one nitrogen atom from the L 2 ligand [Cu-N = 2.170(2) Å] and four oxygen atoms from four 1,3,5-HBTB 2− ligands [Cu-O = 1.9623(19)-1.9763(18)Å], resulting in a distorted square pyramidal geometry, Figure 5a.Two Cu(II) cations are bridged by the 1,3,5-HBTB 2− ligand to form a dinuclear unit with a Cu---Cu distance of 2.6516(6) Å that is shorter than the sum of two van der Waals radius of Cu (2.8 Å), suggesting the presence of weak intermolecular forces.The Cu(II) cations are linked together by 1,3,5-HBTB 2− and L 2 ligands to afford a 3D structure.If the dinuclear Cu(II) units are defined as six-connected nodes, the structure can be simplified as a six-connected net with (4 12 •6 3 )-pcu topology, Figure 5b.The 3D nets penetrate into the neighbors to form a threefold 3D interpenetration structure, Figure 5c, demonstrating that the combination of the flexible L 2 and 1,3,5-HBTB 2− may lead to the formation of the entangled CP [12].
(a)   18) Å], resulting in a distorted square pyramidal geometry, Figure 5a.Two Cu(II) cations are bridged by the 1,3,5-HBTB 2− ligand to form a dinuclear unit with a Cu---Cu distance of 2.6516(6) Å that is shorter than the sum of two van der Waals radius of Cu (2.8 Å), suggesting the presence of weak intermolecular forces.The Cu(II) cations are linked together by 1,3,5-HBTB 2− and L 2 ligands to afford a 3D structure.If the dinuclear Cu(II) units are defined as six-connected nodes, the structure can be simplified as a six-connected net with (4 12 •6 3 )-pcu topology, Figure 5b.The 3D nets penetrate into the neighbors to form a threefold 3D interpenetration structure, Figure 5c, demonstrating that the combination of the flexible L 2 and 1,3,5-HBTB 2− may lead to the formation of the entangled CP [12].

Structure of 3
Complex 3 crystallizes in the monoclinic space group C2/c, and the asymmetric unit comprises one Cu(II) cation, a half of an L 2 ligand and one 1,3,5-HBTB 2− ligand.The Cu(II) cation is coordinated by one nitrogen atom from the L 2 ligand [Cu-N = 2.170(2) Å] and four oxygen atoms from four 1,3,5-HBTB 2− ligands [Cu-O = 1.9623(19)-1.9763(18)Å], resulting in a distorted square pyramidal geometry, Figure 5a.Two Cu(II) cations are bridged by the 1,3,5-HBTB 2− ligand to form a dinuclear unit with a Cu---Cu distance of 2.6516(6) Å that is shorter than the sum of two van der Waals radius of Cu (2.8 Å), suggesting the presence of weak intermolecular forces.The Cu(II) cations are linked together by 1,3,5-HBTB 2− and L 2 ligands to afford a 3D structure.If the dinuclear Cu(II) units are defined as six-connected nodes, the structure can be simplified as a six-connected net with (4 12 •6 3 )-pcu topology, Figure 5b.The 3D nets penetrate into the neighbors to form a threefold 3D interpenetration structure, Figure 5c, demonstrating that the combination of the flexible L 2 and 1,3,5-HBTB 2− may lead to the formation of the entangled CP [12].(a)

Structure of 4
The crystals of complex 4 conform to the monoclinic space group C2/c.The asymmetric unit consists of two Cu(II) cations, a half of an L 3 ligand, one 1,3,5-BTC 3− ligand and one hydroxide ion. Figure 6a

Structure of 4
The crystals of complex 4 conform to the monoclinic space group C2/c.The asymmetric unit consists of two Cu(II) cations, a half of an L 3 ligand, one 1,3,5-BTC 3− ligand and one hydroxide ion. Figure 6a

Structure of 5 and 6
Complexes 5 and 6 crystallize in the orthorhombic space group Pna21.Each of the asymmetric units of 5 and 6 comprise three Cu(II) cations, two L 3 ligands and two 1,3,5-BTB 3− ligands, with an additional two and a half co-crystallized methanol molecules and two co-crystallized water molecules in 5, and two cocrystallized DMF molecules and two co-crystallized water molecules in 6, respectively.Figure 7a 3) is longer that in complex 5, indicating that the Cu(II)---Cu(II) interaction is subject to the nature of the co-crystallized solvent molecules.The Cu(II) cations in 5 and 6 are linked together by 1,3,5-BTB 3− and L 3 ligands to afford 3D structures.If the dinuclear Cu(II) units are defined as six-connected nodes, the mononuclear cations as four-connected nodes and 1,3,5-BTB 3− as three-connected nodes, while the L 3 ligands are defined as linkers, the structures of 5 and 6 can be simplified as 3,4,6-connected 3D nets with the point symbol of (6 3 ) 2 (6 4 •8 2 )(6 8 •8 5 •10 2 ), Figure 7c.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on the torsion angles (θ) of their methylene carbon atoms [0 ≤ θ ≤ 90 • , gauche (G), and 90 < θ ≤ 180 • , anti (A)].On the other hand, cis and trans are given if the two C=O groups are in the same and opposite directions, respectively.Three orientations, syn-syn, syn-anti and anti-anti, are also defined based on the relative position of pyridyl nitrogen and amide oxygen atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.It is also noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations through the two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two pyridyl nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 adopt the same structural type, the ligand conformations of the L 3 ligands are significantly different, presumably due to the difference in the co-crystallized solvents.Moreover, the tricarboxylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination modes, which are also listed in Table 1.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on t sion angles (θ) of their methylene carbon atoms [0 θ 90 o , gauche (G), and 90 180 o , anti (A)].On the other hand, cis and trans are given if the two C=O groups are same and opposite directions, respectively.Three orientations, syn-syn, syn-anti an anti, are also defined based on the relative position of pyridyl nitrogen and amide o atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.It noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations throu two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two p nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 ado same structural type, the ligand conformations of the L 3 ligands are significantly diff presumably due to the difference in the co-crystallized solvents.Moreover, the tric ylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination m which are also listed in Table 1.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on the torsion angles (θ) of their methylene carbon atoms [0 θ 90 o , gauche (G), and 90 θ 180 o , anti (A)].On the other hand, cis and trans are given if the two C=O groups are in the same and opposite directions, respectively.Three orientations, syn-syn, syn-anti and antianti, are also defined based on the relative position of pyridyl nitrogen and amide oxygen atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.It is also noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations through the two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two pyridyl nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 adopt the same structural type, the ligand conformations of the L 3 ligands are significantly different, presumably due to the difference in the co-crystallized solvents.Moreover, the tricarboxylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination modes, which are also listed in Table 1.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on t sion angles (θ) of their methylene carbon atoms [0 θ 90 o , gauche (G), and 90 180 o , anti (A)].On the other hand, cis and trans are given if the two C=O groups are same and opposite directions, respectively.Three orientations, syn-syn, syn-anti an anti, are also defined based on the relative position of pyridyl nitrogen and amide o atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.It noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations throu two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two p nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 ad same structural type, the ligand conformations of the L 3 ligands are significantly di presumably due to the difference in the co-crystallized solvents.Moreover, the tric ylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination which are also listed in Table 1. as six-connected nodes, the mononuclear cations as four-connected nodes and 1,3,5-BTB 3− as three-connected nodes, while the L 3 ligands are defined as linkers, the structures of 5 and 6 can be simplified as 3,4,6-connected 3D nets with the point symbol of ( 63 )2(6 4 •8 2 )(6 8 •8 5 •10 2 ), Figure 7c.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on the torsion angles (θ) of their methylene carbon atoms [0 θ 90 o , gauche (G), and 90 θ 180 o , anti (A)].On the other hand, cis and trans are given if the two C=O groups are in the same and opposite directions, respectively.Three orientations, syn-syn, syn-anti and antianti, are also defined based on the relative position of pyridyl nitrogen and amide oxygen atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.It is also noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations through the two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two pyridyl nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 adopt the same structural type, the ligand conformations of the L 3 ligands are significantly different, presumably due to the difference in the co-crystallized solvents.Moreover, the tricarboxylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination modes, which are also listed in Table 1. as six-connected nodes, the mononuclear cations as four-connected nodes and 1,3,5 as three-connected nodes, while the L 3 ligands are defined as linkers, the structur and 6 can be simplified as 3,4,6-connected 3D nets with the point sym ( 63 )2(6 4 •8 2 )(6 8 •8 5 •10 2 ), Figure 7c.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on t sion angles (θ) of their methylene carbon atoms [0 θ 90 o , gauche (G), and 90 180 o , anti (A)].On the other hand, cis and trans are given if the two C=O groups are same and opposite directions, respectively.Three orientations, syn-syn, syn-anti an anti, are also defined based on the relative position of pyridyl nitrogen and amide atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.I noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations throu two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two p nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 ad same structural type, the ligand conformations of the L 3 ligands are significantly di presumably due to the difference in the co-crystallized solvents.Moreover, the tric ylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination which are also listed in Table 1. as six-connected nodes, the mononuclear cations as four-connected nodes and 1,3,5-BTB 3− as three-connected nodes, while the L 3 ligands are defined as linkers, the structures of 5 and 6 can be simplified as 3,4,6-connected 3D nets with the point symbol of ( 63 )2(6 4 •8 2 )(6 8 •8 5 •10 2 ), Figure 7c.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on the torsion angles (θ) of their methylene carbon atoms [0 θ 90 o , gauche (G), and 90 θ 180 o , anti (A)].On the other hand, cis and trans are given if the two C=O groups are in the same and opposite directions, respectively.Three orientations, syn-syn, syn-anti and antianti, are also defined based on the relative position of pyridyl nitrogen and amide oxygen atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.It is also noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations through the two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two pyridyl nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 adopt the same structural type, the ligand conformations of the L 3 ligands are significantly different, presumably due to the difference in the co-crystallized solvents.Moreover, the tricarboxylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination modes, which are also listed in Table 1. as six-connected nodes, the mononuclear cations as four-connected nodes and 1,3,5 as three-connected nodes, while the L 3 ligands are defined as linkers, the structur and 6 can be simplified as 3,4,6-connected 3D nets with the point sym ( 63 )2(6 4 •8 2 )(6 8 •8 5 •10 2 ), Figure 7c.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on t sion angles (θ) of their methylene carbon atoms [0 θ 90 o , gauche (G), and 90 180 o , anti (A)].On the other hand, cis and trans are given if the two C=O groups are same and opposite directions, respectively.Three orientations, syn-syn, syn-anti an anti, are also defined based on the relative position of pyridyl nitrogen and amide o atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.It noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations throu two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two p nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 ad same structural type, the ligand conformations of the L 3 ligands are significantly diff presumably due to the difference in the co-crystallized solvents.Moreover, the tric ylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination m which are also listed in Table 1.

Ligand Conformations and Coordination Modes
The ligand conformations of the bpba ligands have been proposed based on the torsion angles (θ) of their methylene carbon atoms [0 θ 90 o , gauche (G), and 90 θ 180 o , anti (A)].On the other hand, cis and trans are given if the two C=O groups are in the same and opposite directions, respectively.Three orientations, syn-syn, syn-anti and antianti, are also defined based on the relative position of pyridyl nitrogen and amide oxygen atoms.Accordingly, the ligand conformations of L 1 -L 3 in 1-6 are listed in Table 1.It is also noted that while the bpba ligands in 1, 2, 3, 5 and 6 bridge two Cu(II) cations through the two pyridyl nitrogen atoms, those in 4 bridge four Cu(II) cations through two pyridyl nitrogen and two amide oxygen atoms.Noticeably, although complexes 5 and 6 adopt the same structural type, the ligand conformations of the L 3 ligands are significantly different, presumably due to the difference in the co-crystallized solvents.Moreover, the tricarboxylate ligands in 1-6 bridge two to five Cu(II) cations through various coordination modes, which are also listed in Table 1.

Ligand Conformation
Coordination

Powder X-ray Analysis
In order to check the phase purity of the products, powder X-ray diffraction ( experiments were carried out for all complexes.As shown in Figures S7-S12, th positions of the experimental and simulated PXRD patterns are in agreement wit other, which demonstrates that the crystal structures are truly representative of th materials.The differences in intensity may be owing to the preferred orientation powder samples.

Thermal Properties
Thermal gravimetric analysis (TGA) was carried out to examine the thermal d position from 30 to 800 or 900 °C.The samples were heated in nitrogen gas at a pr of 1 atm with heating rate of 10 °C min −1 , and heating finished at 800 °C or 900 °C, T Figures S13-S18 indicate that complexes 1-6 display two-step weight loss involving of solvent and a loss of organic ligands on heating.

Iodine Adsorption
Radioactive iodine such as 129 I represents one of the most critical nuclear which is harmful to human health and has to be captured and disposed of effective 15].On the other hand, CPs possessing porous structures may facilitate iodine adso through noncovalent interactions involving iodine and various sorption sites.Iod sorption experiments were thus carried out for complexes 1-6 to evaluate the de

Powder X-ray Analysis
In order to check the phase purity of the products, powder X-ray diffraction (PXRD) experiments were carried out for all complexes.As shown in Figures S7-S12, the peak positions of the experimental and simulated PXRD patterns are in agreement with each other, which demonstrates that the crystal structures are truly representative of the bulk materials.The differences in intensity may be owing to the preferred orientation of the powder samples.

Thermal Properties
Thermal gravimetric analysis (TGA) was carried out to examine the thermal decomposition from 30 to 800 or 900 °C.The samples were heated in nitrogen gas at a pressure of 1 atm with heating rate of 10 °C min −1 , and heating finished at 800 °C or 900 °C, Table 2, Figures S13-S18 indicate that complexes 1-6 display two-step weight loss involving a loss of solvent and a loss of organic ligands on heating.

Iodine Adsorption
Radioactive iodine such as 129 I represents one of the most critical nuclear wastes which is harmful to human health and has to be captured and disposed of effectively [13][14][15].On the other hand, CPs possessing porous structures may facilitate iodine adsorption through noncovalent interactions involving iodine and various sorption sites.Iodine adsorption experiments were thus carried out for complexes 1-6 to evaluate the degree of

Powder X-ray Analysis
In order to check the phase purity of the products, powder X-ray diffraction (PXRD) experiments were carried out for all complexes.As shown in Figures S7-S12, the peak positions of the experimental and simulated PXRD patterns are in agreement with each other, which demonstrates that the crystal structures are truly representative of the bulk materials.The differences in intensity may be owing to the preferred orientation of the powder samples.

Thermal Properties
Thermal gravimetric analysis (TGA) was carried out to examine the thermal decomposition from 30 to 800 or 900 • C. The samples were heated in nitrogen gas at a pressure of 1 atm with heating rate of 10 • C min −1 , and heating finished at 800 • C or 900 • C, Table 2, Figures S13-S18 indicate that complexes 1-6 display two-step weight loss involving a loss of solvent and a loss of organic ligands on heating.

Iodine Adsorption
Radioactive iodine such as 129 I represents one of the most critical nuclear wastes which is harmful to human health and has to be captured and disposed of effectively [13][14][15].On the other hand, CPs possessing porous structures may facilitate iodine adsorption through noncovalent interactions involving iodine and various sorption sites.Iodine adsorption experiments were thus carried out for complexes 1-6 to evaluate the degree of adsorption of iodine vapor at 25 and 60 • C within time intervals of 30, 60, 120, 180 and 360 min, respectively.For each experiment, 10 mg of the complex was placed in a 4 mL sample bottle inside a 20 mL sample bottle containing 100 mg of iodine, which was then sealed and kept in the oven.Each experiment was repeated three times and the results averaged.It can be found that the colors of the complexes are different at different temperatures and time intervals, Figures S19-S30.
Tables S1-S12 summarize the I 2 adsorption of 1-6, followed by the plots displaying iodine vapor adsorption rates.With the increase in temperature from 25 to 60 • C, the absorption rate of iodine also has a good increase for each complex, giving the best adsorption factor of 290.0 mg g −1 at 60 • C for 360 min for 5.In order to confirm whether the structures of the iodine-adsorbed complexes remain unchanged, their powder X-ray diffraction (PXRD) patterns were measured.As shown in Figures S31-S42, most of the experimental patterns are consistent with the theoretical ones, but 2 at 60 • C for 30 and 60 min, and 5 and 6 at 60 • C for 60 min display some changes.
The ability of the CPs to adapt iodine molecules to the voids of the network structures may govern the iodine adsorption capacity [16][17][18][19].The solvent accessible volumes calculated by using the PLATON program [20] for 1-6 were 1.5, 17.3, 34.4,2.9, 11.8 and 10.4%, respectively, of the unit cell volume, indicating that complex 3, which displays the three-fold interpenetrated 3D net with (4 12 •6 3 )-pcu topology, may accommodate more iodine than the other complexes.However, the best adsorption factor of 290.0 mg g −1 at 60 • C for 360 min was observed for 5, demonstrating the important role of the flexibility of the neutral spacer ligands, L 1 , L 2 and L 3 , in determining the iodine adsorption capacities of 1-6.The 3D framework of 5 containing the flexible L 3 be more susceptible to the changes in the ligand conformation upon the attack of the iodine molecules and thus may be more appropriate to accommodate the iodine molecules, which can probably be verified by the subtle change in the PXRD pattern of 5, Figure S40, upon iodine adsorption at 60 • C. On the other hand, the framework of the entangled 3 comprising L 2 is not vulnerable to the iodine attack, thus allowing for less iodine adsorption.The different performances in iodine adsorption between 5 and 6 are presumably due to the different co-crystallized solvents.The cavities of these complexes are small and thus most of the adsorptions are, as the reviewer suggested, due to surface uptakes.
We were not able to obtain the crystals suitable for single-crystal X-ray crystallography for the iodine-adsorbed samples.The iodine-adsorbed samples are usually anomalous, and energy dispersive X-ray (EDX) analysis was adopted to confirm iodine adsorption.The EDX experiments demonstrate the existence of the iodine atom rather than the identity of the iodine atom, vide infra.It has been reported that the iodine molecules can be transformed into anionic I 3 − or I 5 − in the iodine-adsorbed CPs [21].Thus, it is not probable to determine whether the adsorption is reversible or irreversible at this moment.
Although the solvent accessible volumes (or the cavity sizes) of the CPs may govern such performances, the identities of the metal centers and the supporting ligands and stabilities of the CPs may also play important roles.The bpba ligands used in this report are well known for their amide groups that may interact with the incoming molecules through hydrogen bonds originating from the amine hydrogen atoms or the carbonyl oxygen atoms.By fixing the similar factors, we have shown that the best adsorption factor of 290.0 mg g −1 at 60 • C for 360 min was observed for 5, demonstrating the important role of the flexibility of the neutral spacer ligands, L 1 , L 2 and L 3 , in determining the iodine adsorption capacities of 1-6.For comparison, it is noted that the interpenetrated Th-SINAP-16 and Th-SINAP-21 appear to exhibit uptake amounts of 354 and 375 mg g −1 , respectively, after 0.5 h of iodine adsorption [21], whereas the Ni(II) CP {[Ni(L 3 )(OBA)(H 2 O) 2 ]•2H 2 O} n encapsulates 166.55 mg g −1 iodine at 60 • C [16].

Energy Dispersive X-ray (EDX) Analysis
EDX analyses were performed for complexes 1-6 after iodine adsorption to investigate their iodine uptakes, Figures S43-S48.Three positions of the iodine-adsorbed samples of complexes 1-6 were selected for each measurement, and the amount of iodine was different for each position, indicating the inhomogeneous distribution of iodine in the iodine-adsorbed samples.
As demonstrated by the experiments, the BET surface area and N 2 uptakes of 1-6 derived from the low-pressure N 2 adsorption and desorption measurements are not closely related to their iodine adsorption capacities.Therefore, the iodine adsorption capacity may also depend on the characteristics of the CPs and their surface features.

X-ray Crystallography
A Bruker AXS SMART APEX II CCD diffractometer, equipped with a graphitemonochromated MoKα radiation (0.71073 Å), was used to collect diffraction data for complexes 1-6.The diffraction data were then reduced by using standard methods [23], followed by empirical absorption corrections based on a "multi-scan".The positions of some of the heavier atoms were located by the direct method or Patterson method, and the remaining atoms were found in a series of alternating difference Fourier maps and leastsquare refinements.The hydrogen atoms, except those of the water molecules, were added by using the HADD command in SHELXTL 6.1012 [24].Due to the serious disordering, the solvent molecules in 3 were squeezed by using the PLATON program [20] and their diffraction data were reported without solvent contribution.Table 3 lists the crystal and structure refinement parameters for 1-6.The CCDC no.2311169-2311174 contains the supplementary crystallographic data for this paper.These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; e-mail: deposit@ccdc.cam.ac.uk; or at http://www.ccdc.cam.ac.uk.

Table 2 .
Thermal properties of complexes 1