Article pubs.acs.org/JACS
Toward Covalent Organic Frameworks Bearing Three Different Kinds of Pores: The Strategy for Construction and COF-to-COF Transformation via Heterogeneous Linker Exchange Cheng Qian,†,‡ Qiao-Yan Qi,‡ Guo-Fang Jiang,† Fu-Zhi Cui,†,‡ Yuan Tian,†,‡ and Xin Zhao*,‡ †
State Key Lab of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China ‡ Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China S Supporting Information *
ABSTRACT: Covalent organic frameworks (COFs) are an emerging class of crystalline porous organic materials which are fabricated via reticular chemistry. Their topologic structures can be precisely predicted on the basis of the structures of building blocks. However, constructing COFs with complicated structures has remained a great challenge, due to the limited strategies that can access to the structural complexity of COFs. In this work, we have developed a new approach to produce COFs bearing three different kinds of pores. The design is fulfilled by the combination of vertex-truncation with multiple-linking-site strategy. On the basis of this design, a “V”-shaped building block carrying two aldehyde groups on the end of each branch has been synthesized. Condensation of it with 1,4-diaminobenzene or benzidine leads to the formation of two triple-pore COFs, TP-COF-DAB and TP-COF-BZ, respectively. The topological structures of the triple-pore COFs have been confirmed by PXRD studies, synchrotron small-angle X-ray scattering (SAXS) experiments, theoretical simulations, and pore size distribution analyses. Furthermore, for the first time, an in situ COF-to-COF transformation has also been achieved by heating TP-COF-BZ with 1,4-diaminobenzene under solvothermal condition, which leads to the formation of TP-COF-DAB via in situ replacing the benzidine linkers in TP-COF-BZ with 1,4-diaminobenzene linkers.
■
INTRODUCTION Covalent organic frameworks (COFs) possess periodic twodimensional (2D) or three-dimensional (3D) network structures formed by linking organic building blocks with dynamic covalent bonds.1 Over the past decade, COFs have attracted a lot of interest due to their versatile applications in many fields, including gas adsorption and storage,2 separation,3 catalysis,4 sensing,5 drug delivery,6 energy storage,7 and opto/ electronic devices.8 As an emerging class of crystalline porous organic materials, the properties and performance of COFs strongly rely on the characters of pores, which is dictated by the topological structures of the networks and their sizes. Traditionally COFs are constructed through the reticular chemistry.9 It means their structures can be precisely predicted on the basis of the structures of the building blocks used for condensation reactions. In this context, the design strategies of COFs have been mainly focused on the combination of building blocks of matched symmetries. In this line, a variety of COFs bearing tetragonal, hexagonal, or even triangular pores have been designed and fabricated since the first two COFs were reported in 2005.10 For those COFs, usually there is only one kind of pore in one COF. As a result, the complexity of COFs is low compared to their analogues metal−organic © 2017 American Chemical Society
frameworks (MOFs), a class of hybrid porous materials comprised of metal ions or clusters connected by organic linkers in their host skeletons through coordination bonds.11 Very recently, a new type of COFs, which bear two or three different kinds of pores in one network, has been developed.12,2h,5b While these heteropore COFs undoubtedly increase the structural complexity and diversity of the COFs family, the strategy for their construction is quite limited, especially for COFs bearing more than two different kinds of pores. The syntheses of COFs follow the principle of dynamic covalent chemistry (DCC), which is based on reversible chemical reactions.13 DCC plays a crucial role in promoting the development of chemistry and materials science. Its dynamic nature allows the exchange of molecular components to achieve thermodynamic minimum of the system under conditions of thermodynamic control. Such a feature is crucial for the syntheses of COFs because it endows the process of COFs formation with self-correction, which secures their crystalline structures. In fact, the construction of COFs has fully taken Received: March 7, 2017 Published: April 26, 2017 6736
DOI: 10.1021/jacs.7b02303 J. Am. Chem. Soc. 2017, 139, 6736−6743
Article
Journal of the American Chemical Society
Scheme 1. (a) Precisely Producing Dual-Pore COFs through Multiple-Linking-Site Strategy (Ref 12e) and (b) Fabricating Triple-Pore COFs by the Combination of Vertex-Truncation Design with Multiple-Linking-Site Strategy (This Work)
Scheme 2. Syntheses and Structures of the Triple-Pore COFs
construction of MOFs, which makes exchanges of building blocks in COFs more difficult. To address the challenges in structural complexity and transformation of COFs, in this work, a new approach, which combines vertex-truncation design15 and multiple-linking-site strategy,12e has been developed to fabricate heteropore COFs bearing three different kinds of pores. Furthermore, for the first time, an in situ COF-to-COF transformation between the triple-pore COFs via heterogeneous linker exchange has also been successfully achieved.
advantage of the reversible feature of DCC to avoid the formation of amorphous structures. However, little attention has been paid to use of the principle of DCC for postsynthesis modification (PSM) of COFs. By contrast, PSM via linker or metal cation replacement in MOFs, which leads to the in situ MOF-to-MOF transformation, has been generally recognized to be a powerful tool to prepare functional MOFs which are difficult or inaccessible via de novo synthesis.14 Considering the common feature of reversible bond formation in both COFs and MOFs, the building-block-exchange-based framework-toframework transformation strategy might also be applicable to COFs. However, while this strategy works well for MOFs, so far COF-to-COF transformation via building block exchange has never been achieved yet, albeit an excellent example of COF-to-COF transformation through chemical conversion of linkage has been reported by the Yaghi group very recently.12k It might be attributed to the fact that the dynamic covalent bonds are inert relative to coordination interactions used for
■
RESULTS AND DISCUSSION As shown in Scheme 1a, the multiple-linking-site strategy based on a C3-symmetric building block has been previously developed by us to precisely construct COFs bearing two different kinds of pores,12e classified as RCSR htb net (P6/ mm).16 In order to produce COFs with more complicated structures, we herein design a new building block by truncating the C3-symmetric monomer, which is illustrated in Scheme 1b. 6737
DOI: 10.1021/jacs.7b02303 J. Am. Chem. Soc. 2017, 139, 6736−6743
Article
Journal of the American Chemical Society
MAS) 13C NMR spectra, which exhibit resonance signals at 157.74 and 158.45 ppm, corresponding to the chemical shift of the newly formed −CN− bonds for TP-COF-DAB and TPCOF-BZ, respectively (Figures S3−4 in Supporting Information). Elemental analyses indicate that the contents of C, H, and N of the as-prepared materials are close to the corresponding theoretical values of the expected COFs (see Supporting Information for details). Thermal stability of the asprepared polymers was assessed by thermogravimetric analysis (TGA) under N2 atm. As revealed by the TGA traces, the lowtemperature onsets of the first derivatives of the traces are 309 and 413 °C for TP-COF-BZ and TP-COF-DAB, respectively (Figures S5−6 in Supporting Information), indicating that they have high thermal stability. The morphologies of the iminebased COFs were investigated by field-emission scanning electron microscopy (FE-SEM) (Figure S7 in Supporting Information). TP-COF-DAB shows fiber-like morphology with uniform sizes. Interestingly, the SEM images indicate that TPCOF-BZ exists as spherical particles and some of them aggregate together. Furthermore, cracked shells of some of the spheres can be directly observed, revealing hollow interior cavities of the spheres. The as-prepared materials were then submitted to powder Xray diffraction (PXRD) analyses to determine their exact crystal structures by comparing their experimental PXRD patterns with the theoretically simulated ones, which were generated by Materials Studios version 7.0. As shown in Figure 1, the (110)
From the topological point of view, when the truncated structure is combined with linear linkers, theoretically two types of 2D frameworks can be produced: one bearing two different kinds of pores (RCSR fes net (C2/mm orthorhombic embedding)) and the other possessing three different kinds of pores (RCSR fxt net (P6/mm)), as shown in Scheme 1b. According to the principle of DCC, the one with the lowest energy will be the major product or even the only product under thermodynamic control conditions, if the energy difference between it and the other isomer is large enough. It creates the possibility of the sole formation of triple-pore COFs. Indeed, the triple-pore COFs turn out to be the only products of the condensation reactions (vide infra). On this basis of the above design, a building block [1,1′:3′,1″-terphenyl]-3,3″,5,5″-tetracarbaldehyde (TPTCA), in which a benzene unit is chosen as the core and two aldehyde groups are introduced to the ends of its two branches, has been designed and synthesized (Scheme 2). Imine is used as a linkage because of its good reversibility. 17 1,4Diaminobenzene and benzidine were selected as the ditopic linear linkers. The COFs were prepared under solvothermal conditions. In order to get COFs with the highest crystallinity, the condensation conditions have been optimized, for which a series of conditions were screened by varying solvent, temperature, and the concentration of acetic acid (see Section C in Supporting Information for all the conditions screened).While the COFs with high crystallinities could be obtained under several conditions, the best conditions were eventually identified as follows. For the COF prepared from TPTCA and 1,4-diaminobenzene (the product was named as TP-COFDAB), a mixture of dimethylacetamide-mesitylene-acetic acid (aq., 3M) (1/21/2.2, v/v/v) is the best among all the solvent systems screened. In the case of the COF produced from the condensation of TPTCA and benzidine (the product was named as TP-COF-BZ), the types of solvents are same, but the ratio changes to 1/12/1.3 (v/v/v) for dimethylacetamidemesitylene-acetic acid (aq., 3M), revealing a significant influence of solvent system on the crystallinity of the COFs. The condensation reactions were carried out in sealed glass ampules at 120 °C for 72 h, which afforded the COFs as yellow powders. They are insoluble in water and common organic solvents. Fourier transform infrared spectroscopy (FT-IR) was used to characterize the as-prepared powders. The IR spectra indicated that the bands at 2739.9 and ∼3350 cm−1, which correspond to the stretching vibrations of C−H of aldehyde groups and the vibrations N−H of amino groups in the starting materials, respectively, were dramatically attenuated after the condensation reactions, suggesting the polymerization degree is considerably high (Figures S1−2 in Supporting Information). Furthermore, the characteristic CN stretching vibration bands were observed at 1618.2 cm−1 for TP-COF-DAB and 1621.7 cm−1 for TP-COF-BZ respectively, which provided compelling evidence for the formation of imine bonds from the condensation of the aldehyde groups of TPTCA and the amino groups of 1,4-diaminobenzene or benzidine. It should be noted that the band corresponding to CO vibration (ca. 1700 cm−1) was still observed in the IR spectra of the COFs, albeit its intensity dramatically decreased relative to that of TATCA. It could be attributed to the terminal aldehyde groups at the edges of the COFs. The formation of the imine bonds was further confirmed by solid-state cross-polarization with magic angle spinning (CP/
Figure 1. (a) Experimental (black) and refined (red) PXRD patterns of TP-COF-DAB, (b) difference plot between experimental and refined PXRD patterns, and simulated PXRD patterns of TPTCAbased (c) triple-pore-AA, (d) triple-pore-AB, (e) dual-pore-AA, and (f) dual-pore-AB structures. 6738
DOI: 10.1021/jacs.7b02303 J. Am. Chem. Soc. 2017, 139, 6736−6743
Article
Journal of the American Chemical Society diffraction peak in the PXRD profile of TP-COF-DAB appears at d-spacing (2θ) 25.33 Å (3.49°). It exhibits strong diffraction intensity, indicating a high crystallinity of the COF. In addition to the (110) peak, diffraction peaks at d-spacing (2θ) 17.93 Å (4.93°), 11.32 Å (7.81°), 8.75 Å (10.10°), 7.97 Å (11.09°), 6.90 Å (12.82°), 6.33 Å (13.97°), 4.94 Å (17.91°), and ca. 3.53 Å (25.07°) are also observed, which are assignable to (210), (400), (330), (510), (610), (800), (820), and (001) diffractions, respectively. Pawley refinement gave the unit-cell parameters of a = 52.20 ± 0.11 Å, b = 52.20 ± 0.11 Å, c = 3.53 ± 0.012 Å, α = β = 90.00° and γ = 120.00°, with Rwp = 5.79% and Rp = 4.09%.18 From the difference plot between the experimental and refined diffraction patterns, it can be found that they match each other very well (Figure 1b). For the structural simulations, four possible crystal structures, that is, triple-pore COF with eclipsed (AA) stacking, triple-pore COF with staggered (AB) stacking, dual-pore COF with eclipsed (AA) stacking and dual-pore COF with staggered (AB) stacking, were constructed. It was found that the experimental PXRD pattern of TP-COF-DAB could be reproduced by the simulated one predicated for a triple-pore COF with AA stacking. This result suggests that the as-formed polymer might possess a framework bearing three different kinds of pores, as that illustrated Scheme 2. Due to the interference of the strong background in low 2θ region, the (100) peak (2θ = 1.95 o) cannot be identified in the experimental PXRD pattern which was performed from small to wide angle. In order to detect the (100) peak, a small angle PXRD experiment was carried out from 1.5° to 5 o, which indeed identified the (100) diffraction at 44.87 Å (1.97°), albeit it appeared as a shoulder peak, as a result of the influence of strong background (Figure S8 in Supporting Information). This result confirms the formation of a triple-pore framework. Moreover, a close comparison of the simulated PXRD patterns of triple-pore and dual-pore COFs reveals that the triple-pore COF exhibits a (210) peak at 5.10°. However, there is no such peak in the simulated PXRD patterns of the dual-pore COF. In the experimental PXRD pattern of TP-COF-DAB, a peak at 2θ = 4.93° was observed, which could be assigned to (210) diffraction, again confirming the triple-pore structure. For the dual-pore COF with AA stacking, the simulation predicted a strong peak assignable to (010) diffraction at 4.49°. This peak, however, was not observed in the experimental PXRD pattern, indicating that dual-pore COF with AA stacking did not form. As shown in Figure 1, for the COF obtained from the condensation of TPTCA and 1,4-diaminobenzene, the most remarkable difference between a triple-pore framework and a dual-pore network lies in the range of 2θ below 2.5°, where the former exhibits a strong diffraction (100), but the latter gives no diffraction peak. To provide more information for this region, a synchrotron small-angle X-ray scattering (SAXS) experiment was carried out. The SAXS profile displays scattering signal at q = 1.39 nm −1 and 2.41 nm −1 , corresponding to d-spacing 4.518 nm (100) and 2.606 nm (110) (Figure 2a,c), respectively. From the SAXS data, the a value of the unit cell of TP-COF-DAB was calculated to be 52.18 and 52.12 Å.19 It is well consistent with the a value obtained from the PXRD data, further confirming the formation of the as-predicted triple-pore COF. Moreover, this result also suggests that SAXS is a useful technique to elucidate the structures of COFs, especially for those with large unit cell sizes. In some cases, their diffraction peaks in a very small 2θ
Figure 2. 2D synchrotron SAXS profiles of (a) TP-COF-DAB and (b) TP-COF-BZ, and their corresponding 1D SAXS profiles of (c) TPCOF-DAB and (d) TP-COF-BZ.
region of PXRD patterns are significantly interfered by the background. Similar to TP-COF-DAB, the crystal structure of TP-COFBZ was also elucidated by comparing the experimental powder X-ray diffraction (PXRD) with the theoretically simulated ones. A series of peaks at d-spacing (2θ) 31.91 Å (2.77°), 15.70 Å (5.63°), 9.39 Å (9.41 o), and 3.93 Å (22.51°) are observed for TP-COF-BZ, which are assignable to (110), (310), (600), and (001) diffractions, respectively (Figure S9 in Supporting Information). Its (100) peak, which was predicted to appear at 2θ = 1.56°, was too small to be observed by PXRD. The refined PXRD profile matches the experimental pattern quite well, which gives unit cell parameters of a = 65.10 ± 0.030 Å, b = 65.10 ± 0.042 Å, c = 3.96 ± 0.0012 Å, α = β = 90.00° and γ = 120.00°, with Rwp = 3.92% and Rp = 2.85%. The comparison of the experimental PXRD pattern with the simulated patterns of the four possible crystal structures suggests a triple-pore COF with AA stacking, which has been further confirmed by the result of a synchrotron SAXS experiment. As shown in Figure 2b,d, scattering peaks with d-spacing of 5.658 nm (100) and 3.254 nm (110) are observed. On the basis of the SAXS data, the a value of the unit cell of the triple-pore COF was calculated to be 65.33 and 65.08 Å, which is very close to the a value derived from the PXRD data. Nitrogen adsorption−desorption measurements revealed that the isotherms of both TP-COF-DAB and TP-COF-BZ exhibited curves similar to the type IV sorption model and displayed a steep nitrogen uptake in the low-pressure range (P/ Po = 0−0.01) (Figure 3).20 On the basis of their N2 isotherm data in the range of P/Po between 0.05 and 0.2, their BET surface areas were calculated to be 302.78 m2/g for TP-COFDAB and 518.94 m2/g for TP-COF-BZ (Figures S10−11 in Supporting Information). Their total pore volumes (at P/Po = 0.99) were calculated to be 0.38 and 0.28 cm3/g for TP-COFDAB and TP-COF-BZ, respectively. The pore size distributions (PSDs) of the two COFs were estimated by using nonlocal density functional theory (NLDFT). Two main distributions around 16.1 and 31.8 Å were observed for TP6739
DOI: 10.1021/jacs.7b02303 J. Am. Chem. Soc. 2017, 139, 6736−6743
Article
Journal of the American Chemical Society
Figure 3. N2 adsorption−desorption isotherms (77 K) of (a) TPCOF-DAB and (c) TP-COF-BZ, and PSD profiles of (b) TP-COFDAB and (d) TP-COF-BZ. Figure 4. PXRD patterns of (a) TP-COF-BZ and (b−e) the samples prepared by heating the mixtures of TP-COF-BZ and different equivalents of 1,4-diaminobenzene (DAB) for 72 h at 120 °C and (f) PXRD pattern of TP-COF-DAB. Note: the diffraction peaks in pattern f after 2θ = 5° seems not as strong as those in patterns d and e. It is because the (110) peak of TP-COF-DAB in pattern f is too strong.
COF-DAB (Figure 3b), which well matched with the theoretical pore sizes of the proposed triple-pore COF (around 18.7 and 30.0 Å, as estimated by PM3 calculations) (Figure S12 in Supporting Information). It should be noted that the rectangle-like pores could not be identified by PSD because they are too narrow to be detected. As revealed by the simulations, the width of the rectangle-like pore is ca. 3.2 Å, which is smaller than the kinetic diameters of N2 (3.64 Å)21 and other gases usually used for PSD analysis such as CO2 (3.3 Å)21 and argon (3.4 Å).22 In the case of TP-COF-BZ, PSD analysis revealed two main distributions around 25.6 and 39.1 Å (Figure 3d). These values are consistent with the simulated pore distributions which were predicted to be around 25.9 and 38.6 Å (Figure S13 in Supporting Information). Similarly, the rectangle-like pores are also unobservable by the PSD analysis. The observation of two peaks in each of the PSD profiles also indicates the formation of triple-pore COFs. If the as-prepared COFs held dual-pore structures, only the larger pore could be detected, and thus just one peak would be observed (Figures S12−13 in Supporting Information). Although the smallest pores are not suitable to encapsulate guests of large size, they might be good for accommodating tiny species such as metal cations. Such application has been demonstrated very recently.2e Compared with TP-COF-DAB, TP-COF-BZ exhibits lower crystallinity and thermal stability. On the other hand, 1,4diaminobenzene should be more active than benzidine, as a result of the electron-donating amine groups at the paraposition. Bearing these facts in mind, we envisioned that TPCOF-BZ might be in situ transformed into TP-COF-DAB through substituting benzidine units in TP-COF-BZ with 1,4diaminobenzene. On the basis of this design, COF-to-COF transformation was thus investigated by introducing different equivalents of 1,4-diaminobenzene into suspensions of the premade TP-COF-BZ in dimethylacetamide-mesitylene-acetic acid (aq., 3M)(1/21/2.2, v/v/v). The mixtures were heated in sealed glass tubes at 120 °C for 72 h, and then the as-obtained materials were submitted to PXRD analysis after being thoroughly washed with anhydrous 1,4-dioxane. As can be seen in Figure 4, for the entry of the addition of 2 equiv of 1,4diaminobenzene, the peak corresponding to the (110)
diffraction of TP-COF-DAB is barely observed, suggesting that 2 equiv of 1,4-diaminobenzene does not work well for transformation. To drive the equilibrium toward TP-COFDAB, excessive 1,4-diaminobenzene was added. The asrecorded PXRD patterns show that the intensity of (110) peak of TP-COF-DAB increases with increasing amounts of 1,4-diaminobenzene. The addition of 10 equiv of 1,4diaminobenzene gives rise to the best result. The material obtained under this condition exhibits almost identical PXRD to that of TP-COF-DAB prepared by the direct condensation of TPTCA and 1,4-diaminobenzene, not only in number and position of the peaks but also in the relative intensities of the peaks. Extending the reaction time from 3 days to 4 and 5 days made no change in the PXRD patterns (Figure S14 in Supporting Information). These results clearly indicate that TP-COF-BZ has been successfully transformed into TP-COFDAB through in situ substitution of benzidine units with 1,4diminobenzene. The transformation of TP-COF-BZ into TPCOF-DAB has also been supported by the result of comparison of the IR spectra before and after the transformation with the IR spectrum of standard TP-COF-DAB obtained via de novo synthesis. While TP-COF-BZ exhibits the CN stretching vibration at 1621.7 cm−1, the powder generated by the transformation experiment displays the vibration at 1618.6 cm−1, which is almost the same as that of the standard TPCOF-DAB (1618.2 cm −1 ) (Figure S15 in Supporting Information), indicating again the formation of TP-COFDAB via linker exchange. To get a deeper insight into the COF-to-COF transformation process, a time-dependent transformation experiment was carried out. Ten equiv of 1,4-diaminobenzene was added into a series of suspensions of premade TP-COF-BZ in dimethylacetamide-mesitylene-acetic acid (aq., 3M)(1/21/2.2, 6740
DOI: 10.1021/jacs.7b02303 J. Am. Chem. Soc. 2017, 139, 6736−6743
Article
Journal of the American Chemical Society
90.94%, 95.49%, and 97.23%, respectively (Figure S17 in Supporting Information), also indicating an almost complete transformation after 4 h. The transformation process was followed by photographing. Retention of insoluble materials was observed throughout the whole transformation course (Figure S18 in Supporting Information). On the other hand, the insoluble materials at different transformation time intervals have already been confirmed by the above 1H NMR spectroscopic study to be the outcomes of incompletely and/or completely transformed COF. A previous research reported that precipitation of a COF from solution is an irreversible process.23 It does not dissolve and go back to monomers again once the polymeric structure has formed. These results clearly indicate that exchange of linkers proceeds in a heterogeneous way. Moreover, they also rule out an exchange mechanism through dissolution and reprecipitation. On the basis of the above experimental results, a transformation mechanism, as illustrated in Figure 6, has been
v/v/v), and the mixtures were heated in sealed glass tubes at 120 °C for 0.5, 1, 2, 4, 8, and 16 h, respectively. The PXRD analyses revealed that the materials prepared at 4, 8, and 16 h exhibit almost the same PXRD pattern, and the patterns are nearly identical to that of TP-COF-DAB directly prepared from TPTCA and 1,4-diaminobenzene (Figure 5). In the case of 0.5
Figure 5. PXRD patterns of the samples prepared by heating a mixture of TP-COF-BZ and 1,4-diaminobenzene (10 equiv) at different time intervals.
h, the as-obtained material just displays several peaks which are hard to identify. In its PXRD pattern, the diffraction peaks corresponding to TP-COF-BZ totally disappear, but no peaks of TP-COF-DAB can be observed. This result suggests that substitution of benzidine units with 1,4-diminobenzene has already begun, which deassembled the network of TP-COFBZ, but TP-COF-DAB has not formed at this time. When the reaction time was extended to 1 h, formation of TP-COF-DAB could be observed, albeit its crystallinity was not high. Extending the reaction time to 2 h improved the crystallinity, as indicated by the observation of the peaks in the range of 2θ = 7.5−30°. After 4 h, the transformation has nearly completed. This result not only unambiguously confirms the COF-to-COF transformation again but also suggests that it is a quick process. The percent of linker exchange with respect to time was then assessed. It should be pointed out that it cannot be monitored by PRXD because only the starting COF (TP-COF-BZ) and the product COF (TP-COF-DAB) can be detected by PXRD. The intermediates of partial replacement should lose crystallinity, which means that they are amorphous and thus cannot be detected by PXRD when they coexist with the COFs. Therefore, the content of linker exchanged with respect to time was monitored with 1H NMR spectroscopy by analyzing the ratio of 1,4-diaminobenzene/benzidine in the polymers obtained at different transformation time intervals after these insoluble materials were completely hydrolyzed (Figure S16 in Supporting Information) . It was found that the molar percentages of 1,4-diaminobenzene and benzidine were 54.55% and 45.45%, respectively, for the sample at 0.5 h. Extending the time to 1 h led to the molar percentage of 1,4diaminobenzene increasing to 88.89%. In the cases of 2, 4, and 8 h, the molar percentages of 1,4-diaminobenzene increase to
Figure 6. Proposed process for the in situ transformation of TP-COFBZ into TP-COF-DAB in the presence of 1,4-diaminobenzene. Note: Only one unit was illustrated for clarity.
proposed. Due to the porous nature of COFs, a large amount of 1,4-diamionbenzene in solution can readily diffuse into the channels of solid TP-COF-BZ and then nucleophilically attack its imine bonds catalyzed by acetic acid. Subsequently, a benzidine molecule is released after the formation of new imine bonds between 1,4-diamionbenzene and the aldehydes which condensed with it before. Following this process, benzidine units are gradually replaced by 1,4-diamionbenzene segments and eventually all the benzidine linkers in TP-COF-BZ have been replaced by 1,4-diamionbenzene linkers, which leads to the formation of TP-COF-DAB. During the transformation, the polymers (TP-COF-BZ, intermediates of partial replacement and TP-COF-DAB) exist as insoluble solids, and the diamines stay in solution. The replacement reactions should occur at the solid-solution interface. 6741
DOI: 10.1021/jacs.7b02303 J. Am. Chem. Soc. 2017, 139, 6736−6743
Article
Journal of the American Chemical Society
■
T. E.; Ding, R.; El-Kaderi, H. M. Chem. - Eur. J. 2013, 19, 3324−3328. (e) Baldwin, L. A.; Crowe, J. W.; Pyles, D. A.; McGrier, P. L. J. Am. Chem. Soc. 2016, 138, 15134−15137. (f) Zeng, Y.; Zou, R.; Zhao, Y. Adv. Mater. 2016, 28, 2855−2873. (g) Li, Z.; Zhi, Y.; Feng, X.; Ding, X.; Zou, Y.; Liu, X.; Mu, Y. Chem. - Eur. J. 2015, 21, 12079−12084. (h) Du, Y.; Yang, H.; Whiteley, J. M.; Wan, S.; Jin, Y.; Lee, S.-H.; Zhang, W. Angew. Chem., Int. Ed. 2016, 55, 1737−1741. (3) (a) Kang, Z.; Peng, Y.; Qian, Y.; Yuan, D.; Addicoat, M. A.; Heine, T.; Hu, Z.; Tee, L.; Guo, Z.; Zhao, D. Chem. Mater. 2016, 28, 1277−1285. (b) Kandambeth, S.; Biswal, B. P.; Chaudhari, H. D.; Rout, K. C.; Kunjattu, H. S.; Mitra, S.; Karak, S.; Das, A.; Mukherjee, R.; Kharul, U. K.; Banerjee, R. Adv. Mater. 2017, 29, 1603945. (c) Ma, H.; Ren, H.; Meng, S.; Yan, Z.; Zhao, H.; Sun, F.; Zhu, G. Chem. Commun. 2013, 49, 9773−9775. (d) Oh, H.; Kalidindi, S. B.; Um, Y.; Bureekaew, S.; Schmid, R.; Fischer, R. A.; Hirscher, M. Angew. Chem., Int. Ed. 2013, 52, 13219−13222. (4) (a) Ding, S.-Y.; Gao, J.; Wang, Q.; Zhang, Y.; Song, W.-G.; Su, C.-Y.; Wang, W. J. Am. Chem. Soc. 2011, 133, 19816−19822. (b) Shinde, D. B.; Kandambeth, S.; Pachfule, P.; Kumar, R. R.; Banerjee, R. Chem. Commun. 2015, 51, 310−313. (c) Xu, H.-S.; Ding, S.-Y.; An, W.-K.; Wu, H.; Wang, W. J. Am. Chem. Soc. 2016, 138, 11489−11492. (d) Wang, X.; Han, X.; Zhang, J.; Wu, X.; Liu, Y.; Cui, Y. J. Am. Chem. Soc. 2016, 138, 12332−12335. (e) Sun, Q.; Aguila, B.; Perman, J.; Nguyen, N.; Ma, S. J. Am. Chem. Soc. 2016, 138, 15790− 15796. (f) Xu, H.; Gao, J.; Jiang, D. Nat. Chem. 2015, 7, 905−912. (g) Fang, Q.; Gu, S.; Zheng, J.; Zhuang, Z.; Qiu, S.; Yan, Y. Angew. Chem., Int. Ed. 2014, 53, 2878−2882. (h) Vyas, V. S.; Haase, F.; Stegbauer, L.; Savasci, G.; Podjaski, F.; Ochsenfeld, C.; Lotsch, B. V. Nat. Commun. 2015, 6, 8508. (i) Lin, S.; Diercks, C. S.; Zhang, Y.-B.; Kornienko, N.; Nichols, E. M.; Zhao, Y.; Paris, A. R.; Kim, D.; Yang, P.; Yaghi, O. M.; Chang, C. J. Science 2015, 349, 1208−1213. (5) (a) Lin, G.; Ding, H.; Yuan, D.; Wang, B.; Wang, C. J. Am. Chem. Soc. 2016, 138, 3302−3305. (b) Dalapati, S.; Jin, E.; Addicoat, M.; Heine, T.; Jiang, D. J. Am. Chem. Soc. 2016, 138, 5797−5800. (c) Ding, S.-Y.; Dong, M.; Wang, Y.-W.; Chen, Y.-T.; Wang, H.-Z.; Su, C.-Y.; Wang, W. J. Am. Chem. Soc. 2016, 138, 3031−3037. (d) Das, G.; Biswal, B. P.; Kandambeth, S.; Venkatesh, V.; Kaur, G.; Addicoat, M.; Heine, T.; Verma, S.; Banerjee, R. Chem. Sci. 2015, 6, 3931−3939. (e) Xie, Y.-F.; Ding, S.-Y.; Liu, J.-M.; Wang, W.; Zheng, Q.-Y. J. Mater. Chem. C 2015, 3, 10066−10069. (6) (a) Fang, Q.; Wang, J.; Gu, S.; Kaspar, R. B.; Zhuang, Z.; Zheng, J.; Guo, H.; Qiu, S.; Yan, Y. J. Am. Chem. Soc. 2015, 137, 8352−8355. (b) Bai, L.; Phua, S. Z. F.; Lim, W. Q.; Jana, A.; Luo, Z.; Tham, H. P.; Zhao, L.; Gao, Q.; Zhao, Y. Chem. Commun. 2016, 52, 4128−4131. (c) Vyas, V. S.; Vishwakarma, M.; Moudrakovski, I.; Haase, F.; Savasci, G.; Ochsenfeld, C.; Spatz, J. P.; Lotsch, B. V. Adv. Mater. 2016, 28, 8749−8754. (7) (a) DeBlase, C. R.; Silberstein, K. E.; Truong, T.-T.; Abruña, H. D.; Dichtel, W. R. J. Am. Chem. Soc. 2013, 135, 16821−16824. (b) Xu, F.; Xu, H.; Chen, X.; Wu, D.; Wu, Y.; Liu, H.; Gu, C.; Fu, R.; Jiang, D. Angew. Chem., Int. Ed. 2015, 54, 6814−6818. (c) Liao, H.; Wang, H.; Ding, H.; Meng, X.; Xu, H.; Wang, B.; Ai, X.; Wang, C. J. Mater. Chem. A 2016, 4, 7416−7421. (d) DeBlase, C. R.; Hernández-Burgos, K.; Silberstein, K. E.; Rodríguez-Calero, G. G.; Bisbey, R. P.; Abruña, H. D.; Dichtel, W. R. ACS Nano 2015, 9, 3178−3183. (e) Mulzer, C. R.; Shen, L.; Bisbey, R. P.; McKone, J. R.; Zhang, N.; Abruña, H. D.; Dichtel, W. R. ACS Cent. Sci. 2016, 2, 667−673. (8) (a) Wan, S.; Gándara, F.; Asano, A.; Furukawa, H.; Saeki, A.; Dey, S. K.; Liao, L.; Ambrogio, M. W.; Botros, Y. Y.; Duan, X.; Seki, S.; Stoddart, J. F.; Yaghi, O. M. Chem. Mater. 2011, 23, 4094−4097. (b) Chen, L.; Furukawa, K.; Gao, J.; Nagai, A.; Nakamura, T.; Dong, Y.; Jiang, D. J. Am. Chem. Soc. 2014, 136, 9806−9809. (c) Calik, M.; Auras, F.; Salonen, L. M.; Bader, K.; Grill, I.; Handloser, M.; Medina, D. D.; Dogru, M.; Löbermann, F.; Trauner, D.; Hartschuh, A.; Bein, T. J. Am. Chem. Soc. 2014, 136, 17802−17807. (d) Cai, S.-L.; Zhang, Y.B.; Pun, A. B.; He, B.; Yang, J.; Toma, F. M.; Sharp, I. D.; Yaghi, O. M.; Fan, J.; Zheng, S.-R.; Zhang, W.-G.; Liu, Y. Chem. Sci. 2014, 5, 4693−4700. (e) Feldblyum, J. I.; McCreery, C. H.; Andrews, S. C.;
CONCLUSION In conclusion, a new strategy for construction of 2D COFs with complicated topological structures has been developed. This strategy is to combine the vertex-truncation and the multiplelinking-site design. Implementation of the strategy leads to the successful construction of two novel 2D COFs which bear three different kinds of pores in one network. Furthermore, the principle of dynamic covalent chemistry has also been applied in the postsynthesis modification of COFs, through which the first example of COF-to-COF transformation via heterogeneous linker exchange has been realized. This work not only indicates that highly complicated 2D polymeric structures can be facilely constructed from simple building blocks but also suggests a promising way to fabricate COFs which are difficult or unattainable under de novo synthetic conditions through the transformation of COFs facilely accessible, which sheds new light on the development of new strategies for the construction of crystalline porous organic materials. The obtention of the COFs with complicated topologic structures lays the foundation for integrating multiple functions into one framework, which is crucial for the fabrication of advanced materials. On the other hand, the in situ COF-to-COF transformation might also offer a new avenue for functionalization and property modification of COFs via structural doping. The investigations on such potentials are currently underway in our laboratory.
■
ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.7b02303. Procedures for the preparation of the monomer and COFs, FT-IR spectra, solid-state 13C CP-MAS NMR spectra, SEM images, BET plots, TGA traces and fractional atomic coordinates for the unit cells of the COFs (PDF)
■
AUTHOR INFORMATION
Corresponding Author
*
[email protected] ORCID
Xin Zhao: 0000-0002-1317-7257 Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS We thank the National Natural Science Foundation of China (nos. 21472225, 21632004, and 51578224) and the Strategic Priority Research Program of the Chinese Academy of Sciences (grant no. XDB20000000) for financial support. We also thank the Shanghai Synchrotron Radiation Facility for collecting the synchrotron small-angle X-ray scattering data.
■
REFERENCES
(1) (a) Waller, P. J.; Gándara, F.; Yaghi, O. M. Acc. Chem. Res. 2015, 48, 3053−3063. (b) Jiang, J.; Zhao, Y.; Yaghi, O. M. J. Am. Chem. Soc. 2016, 138, 3255−3265. (2) (a) Doonan, C. J.; Tranchemontagne, D. J.; Glover, T. G.; Hunt, J. R.; Yaghi, O. M. Nat. Chem. 2010, 2, 235−238. (b) Furukawa, H.; Yaghi, O. M. J. Am. Chem. Soc. 2009, 131, 8875−8883. (c) Song, J.-R.; Sun, J.; Liu, J.; Huang, Z.-T.; Zheng, Q.-Y. Chem. Commun. 2014, 50, 788−791. (d) Rabbani, M. G.; Sekizkardes, A. K.; Kahveci, Z.; Reich, 6742
DOI: 10.1021/jacs.7b02303 J. Am. Chem. Soc. 2017, 139, 6736−6743
Article
Journal of the American Chemical Society Kurosawa, T.; Santos, E. J. G.; Duong, V.; Fang, L.; Ayzner, A. L.; Bao, Z. Chem. Commun. 2015, 51, 13894−13897. (9) Yaghi, O. M. J. Am. Chem. Soc. 2016, 138, 15507−15509. (10) (a) Côté, A. P.; Benin, A. I.; Ockwig, N. W.; O’Keeffe, M.; Matzger, A. J.; Yaghi, O. M. Science 2005, 310, 1166−1170. (b) Feng, X.; Ding, X.; Jiang, D. Chem. Soc. Rev. 2012, 41, 6010−6022. (c) Ding, S. Y.; Wang, W. Chem. Soc. Rev. 2013, 42, 548−568. (d) Wang, H.; Ding, H.; Meng, X.; Wang, C. Chin. Chem. Lett. 2016, 27, 1376−1382. (e) Segura, J. L.; Mancheño, M. J.; Zamora, F. Chem. Soc. Rev. 2016, 45, 5635−5671. (11) (a) Schoedel, A.; Li, M.; Li, D.; O’Keeffe, M.; Yaghi, O. M. Chem. Rev. 2016, 116, 12466−12535. (b) Zhang, M.; Bosch, M.; Gentle, T., III; Zhou, H.-C. CrystEngComm 2014, 16, 4069−4083. (12) (a) Zhou, T.-Y.; Xu, S.-Q.; Wen, Q.; Pang, Z.-F.; Zhao, X. J. Am. Chem. Soc. 2014, 136, 15885−15888. (b) Pang, Z.-F.; Xu, S.-Q.; Zhou, T.-Y.; Liang, R.-R.; Zhan, T.-G.; Zhao, X. J. Am. Chem. Soc. 2016, 138, 4710−4713. (c) Xu, S.-Q.; Zhan, T.-G.; Wen, Q.; Pang, Z.-F.; Zhao, X. ACS Macro Lett. 2016, 5, 99−102. (d) Tian, Y.; Xu, S.-Q.; Qian, C.; Pang, Z.-F.; Jiang, G.-F.; Zhao, X. Chem. Commun. 2016, 52, 11704− 11707. (e) Qian, C.; Xu, S.-Q.; Jiang, G.-F.; Zhan, T.-G.; Zhao, X. Chem. - Eur. J. 2016, 22, 17784−17789. (f) Baldwin, L. A.; Crowe, J. W.; Shannon, M. D.; Jaroniec, C. P.; McGrier, P. L. Chem. Mater. 2015, 27, 6169−6172. (g) Yang, H.; Du, Y.; Wan, S.; Trahan, G. D.; Jin, Y.; Zhang, W. Chem. Sci. 2015, 6, 4049−4053. (h) Crowe, J. W.; Baldwin, L. A.; McGrier, P. L. J. Am. Chem. Soc. 2016, 138, 10120− 10123. (i) Zhu, Y.; Wan, S.; Jin, Y.; Zhang, W. J. Am. Chem. Soc. 2015, 137, 13772−13775. (j) Ascherl, L.; Sick, T.; Margraf, J. T.; Lapidus, S. H.; Calik, M.; Hettstedt, C.; Karaghiosoff, K.; Döblinger, M.; Clark, T.; Chapmen, K. W.; Auras, F.; Bein, T. Nat. Chem. 2016, 8, 310−316. (k) Waller, P. J.; Lyle, S. J.; Popp, T. M. O.; Diercks, C. S.; Reimer, J. A.; Yaghi, O. M. J. Am. Chem. Soc. 2016, 138, 15519−15522. (13) (a) Rowan, S. J.; Cantrill, S. J.; Cousins, G. R. L.; Sanders, J. K. M; Stoddart, J. F. Angew. Chem., Int. Ed. 2002, 41, 898−952. (b) Corbett, P. T.; Leclaire, J.; Vial, L.; West, K. R.; Wietor, J.-L.; Sanders, J. K. M.; Otto, S. Chem. Rev. 2006, 106, 3652−3711. (c) Jin, Y.; Yu, C.; Denman, R. J.; Zhang, W. Chem. Soc. Rev. 2013, 42, 6634− 6654. (d) Wilson, A.; Gasparini, G.; Matile, S. Chem. Soc. Rev. 2014, 43, 1948−1962. (e) Roy, N.; Bruchmann, B.; Lehn, J.-M. Chem. Soc. Rev. 2015, 44, 3786−3807. (14) (a) Deria, P.; Mondloch, J. E.; Karagiaridi, O.; Bury, W.; Hupp, J. T.; Farha, O. K. Chem. Soc. Rev. 2014, 43, 5896−5912. (b) Karagiaridi, O.; Bury, W.; Mondloch, J. E.; Hupp, J. T.; Farha, O. K. Angew. Chem., Int. Ed. 2014, 53, 4530−4540. (c) Lalonde, M.; Bury, W.; Karagiaridi, O.; Brown, Z.; Hupp, J. T.; Farha, O. K. J. Mater. Chem. A 2013, 1, 5453−5468. (d) Han, Y.; Li, J.-R.; Xie, Y.; Guo, G. Chem. Soc. Rev. 2014, 43, 5952−5981. (e) Burnett, B. J.; Barron, P. M.; Hu, C.; Choe, W. J. Am. Chem. Soc. 2011, 133, 9984−9987. (f) Kim, M.; Cahill, J. F.; Su, Y.; Prather, K. A.; Cohen, S. M. Chem. Sci. 2012, 3, 126−130. (g) Karagiaridi, O.; Bury, W.; Tylianakis, E.; Sarjeant, A. A.; Hupp, J. T.; Farha, O. K. Chem. Mater. 2013, 25, 3499−3503. (15) Bunck, D. N.; Dichtel, W. R. Chem. - Eur. J. 2013, 19, 818−827 and references therein.. (16) O’Keeffe, M.; Peskov, M. A.; Ramsden, S. J.; Yaghi, O. M. Acc. Chem. Res. 2008, 41, 1782−1789. (17) Uribe-Romo, F. J.; Hunt, J. R.; Furukawa, H.; Klöck, C.; O’Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2009, 131, 4570−4571. (18) It should be pointed out that Pawley refinement cannot be utilized to fully describe the COF because this algorithm only refines the unit cell parameters and not the content of the unit cell. A full solution of the structure including the contents of the unit cell can only be achieved through the Rietveld routine. (19) The a value was calculated through the equation for the 3
(21) Chen, K.-J.; Madden, D. G.; Pham, T.; Forrest, K. A.; Kumar, A.; Yang, Q.-Y.; Xue, W.; Space, B.; Perry, J. J., IV; Zhang, J.-P.; Chen, X.M.; Zaworotko, M. J. Angew. Chem., Int. Ed. 2016, 55, 10268−10272. (22) Rosi, N. L.; Kim, J.; Eddaoudi, M.; Chen, B.; O’Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2005, 127, 1504−1518. (23) Smith, B. J.; Dichtel, W. R. J. Am. Chem. Soc. 2014, 136, 8783− 8789.
1
hexagonal lattice: d(100)= 2 a , d(110) = 2 a , respectively. (20) Sing, K. S. W.; Everett, D. H.; Haul, R. A. W.; Moscou, L.; Pierotti, R. A.; Rouquérol, J.; Siemieniewska, T. Pure Appl. Chem. 1985, 57, 603−619. 6743
DOI: 10.1021/jacs.7b02303 J. Am. Chem. Soc. 2017, 139, 6736−6743
