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Addicoat M, Bennett TD, Brammer L, Craig G, Das C, Dichtel W, Doan H, Evans AM, Evans J, Goodwin A, Horike S, Jiang J, Kaskel S, Kato M, Kitagawa S, Kobayashi A, Krause S, Lavenn C, Lee JSM, Phillips AE, Roseveare TM, Schmid R, Shivanna M, Sirbu D, Tashiro S, Ting VP, van der Veen MA, Wilson B, Zhao P. Materials breaking the rules: general discussion. Faraday Discuss 2021; 225:255-270. [PMID: 33475107 DOI: 10.1039/d0fd90033h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Robison L, Gong X, Evans AM, Son FA, Wang X, Redfern LR, Wasson MC, Syed ZH, Chen Z, Idrees KB, Islamoglu T, Delferro M, Dichtel WR, Coudert FX, Gianneschi NC, Farha OK. Transient Catenation in a Zirconium-Based Metal-Organic Framework and Its Effect on Mechanical Stability and Sorption Properties. J Am Chem Soc 2021; 143:1503-1512. [PMID: 33433209 DOI: 10.1021/jacs.0c11266] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Interpenetration of two or more sublattices is common among many metal-organic frameworks (MOFs). Herein, we study the evolution of one zirconium cluster-based, 3,8-connected MOF from its non-interpenetrated (NU-1200) to interpenetrated (STA-26) isomer. We observe this transient catenation process indirectly using ensemble methods, such as nitrogen porosimetry and X-ray diffraction, and directly, using high-resolution transmission electron microscopy. The approach detailed here will serve as a template for other researchers to monitor the interpenetration of their MOF samples at the bulk and single-particle limits. We investigate the mechanical stability of both lattices experimentally by pressurized in situ X-ray diffraction and nanoindentation as well as computationally with density functional theory calculations. Both lines of study reveal that STA-26 is considerably more mechanically stable than NU-1200. We conclude this study by demonstrating the potential of these MOFs and their mixed phases for the capture of gaseous n-hexane, used as a structural mimic for the chemical warfare agent sulfur mustard gas.
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Li K, Wong NK, Strauss MJ, Evans AM, Matsumoto M, Dichtel WR, Adronov A. Postsynthetic Modification of a Covalent Organic Framework Achieved via Strain-Promoted Cycloaddition. J Am Chem Soc 2021; 143:649-656. [DOI: 10.1021/jacs.0c11811] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Balch HB, Evans AM, Dasari RR, Li H, Li R, Thomas S, Wang D, Bisbey RP, Slicker K, Castano I, Xun S, Jiang L, Zhu C, Gianneschi N, Ralph DC, Brédas JL, Marder SR, Dichtel WR, Wang F. Electronically Coupled 2D Polymer/MoS 2 Heterostructures. J Am Chem Soc 2020; 142:21131-21139. [PMID: 33284624 PMCID: PMC9836045 DOI: 10.1021/jacs.0c10151] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Emergent quantum phenomena in electronically coupled two-dimensional heterostructures are central to next-generation optical, electronic, and quantum information applications. Tailoring electronic band gaps in coupled heterostructures would permit control of such phenomena and is the subject of significant research interest. Two-dimensional polymers (2DPs) offer a compelling route to tailored band structures through the selection of molecular constituents. However, despite the promise of synthetic flexibility and electronic design, fabrication of 2DPs that form electronically coupled 2D heterostructures remains an outstanding challenge. Here, we report the rational design and optimized synthesis of electronically coupled semiconducting 2DP/2D transition metal dichalcogenide van der Waals heterostructures, demonstrate direct exfoliation of the highly crystalline and oriented 2DP films down to a few nanometers, and present the first thickness-dependent study of 2DP/MoS2 heterostructures. Control over the 2DP layers reveals enhancement of the 2DP photoluminescence by two orders of magnitude in ultrathin sheets and an unexpected thickness-dependent modulation of the ultrafast excited state dynamics in the 2DP/MoS2 heterostructure. These results provide fundamental insight into the electronic structure of 2DPs and present a route to tune emergent quantum phenomena in 2DP hybrid van der Waals heterostructures.
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Evans AM, Ryder MR, Ji W, Strauss MJ, Corcos AR, Vitaku E, Flanders NC, Bisbey RP, Dichtel WR. Trends in the thermal stability of two-dimensional covalent organic frameworks. Faraday Discuss 2020; 225:226-240. [PMID: 33201970 DOI: 10.1039/d0fd00054j] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two-dimensional covalent organic frameworks (2D COFs) are synthetically diverse, layered macromolecules. Their covalent lattices are thought to confer high thermal stability, which is typically evaluated with thermogravimetric analysis (TGA). However, TGA measures the temperature at which volatile degradation products are formed and is insensitive to changes of the periodic structure of the COF. Here, we study the thermal stability of ten 2D COFs using a combination of variable-temperature X-ray diffraction, TGA, diffuse reflectance infrared spectroscopy, and density functional theory calculations. We find that 2D COFs undergo a general two-step thermal degradation process. At the first degradation temperature, 2D COFs lose their crystallinity without chemical degradation. Then, at higher temperatures, they chemically degrade into volatile byproducts. Several trends emerge from this exploration of 2D COF stability. Boronate ester-linked COFs are generally more thermally stable than comparable imine-linked COFs. Smaller crystalline lattices are more robust to thermal degradation than chemically similar larger lattices. Finally, pore-functionalized COFs degrade at significantly lower temperatures than their unfunctionalized analogues. These trends offer design criteria for thermally resilient 2D COF materials. These findings will inform and encourage a broader exploration of mechanical deformation in 2D networks, providing a necessary step towards their practical use.
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Feriante C, Evans AM, Jhulki S, Castano I, Strauss MJ, Barlow S, Dichtel WR, Marder SR. New Mechanistic Insights into the Formation of Imine-Linked Two-Dimensional Covalent Organic Frameworks. J Am Chem Soc 2020; 142:18637-18644. [PMID: 33058663 DOI: 10.1021/jacs.0c08390] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A more robust mechanistic understanding of imine-linked two-dimensional covalent organic frameworks (2D COFs) is needed to improve their crystalline domain sizes and to control their morphology, both of which are necessary to fully realize their application potential. Here, we present evidence that 2D imine-linked COFs rapidly polymerize as crystalline sheets that subsequently reorganize to form stacked structures. Primarily, this study focuses on the first few minutes of 1,3,5-tris(4-aminophenyl)benzene and terephthaldehyde polymerization, which yields an imine-linked 2D COF. In situ X-ray diffraction and thorough characterization of solids obtained using gentler isolation and activation methods than have typically been used in the literature indicate that periodic imine-linked 2D structures form within 60 s, which then form more ordered stacked structures over the course of several hours. This stacking process imparts improved stability toward the isolation process relative to that of the early stage materials, which likely obfuscated previous mechanistic conclusions regarding 2D polymerization that were based on products isolated using harsh activation methods. This revised mechanistic picture has useful implications; the 2D COF layers isolated at very short reaction times are easily exfoliated, as observed in this work using high-resolution transmission electron microscopy and atomic force microscopy. These results suggest improved control of imine-linked 2D COF formation can be obtained through manipulation of the polymerization conditions and interlayer interactions. Qualitatively similar results were obtained for analogous materials obtained from 2,5-di(alkoxy)terephthaldehyde derivatives, except for the COF with the longest alkoxy chains examined (OC12H25), which, although shown by in situ X-ray diffraction to be highly crystalline in the reaction mixture, is much less crystalline when isolated than the other COFs examined, likely due to the more severe steric impact of the dodecyloxy functionality on the stacking process.
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Evans AM, Bradshaw NP, Litchfield B, Strauss MJ, Seckman B, Ryder MR, Castano I, Gilmore C, Gianneschi NC, Mulzer CR, Hersam MC, Dichtel WR. High-Sensitivity Acoustic Molecular Sensors Based on Large-Area, Spray-Coated 2D Covalent Organic Frameworks. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2004205. [PMID: 32939866 DOI: 10.1002/adma.202004205] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/07/2020] [Indexed: 06/11/2023]
Abstract
2D covalent organic frameworks (2D COFs) are a unique materials platform that combines covalent connectivity, structural regularity, and molecularly precise porosity. However, 2D COFs typically form insoluble aggregates, thus limiting their processing via additive manufacturing techniques. In this work, colloidal suspensions of boronate-ester-linked 2D COFs are used as a spray-coating ink to produce large-area 2D COF thin films. This method is synthetically general, with five different 2D COFs prepared as colloidal inks and subsequently spray-coated onto a diverse range of substrates. Moreover, this approach enables the deposition of multiple 2D COF materials simultaneously, which is not possible by polymerizing COFs on substrates directly. When combined with stencil masks, spray-coated 2D COFs are rapidly deposited as thin films larger than 200 cm2 with line resolutions below 50 µm. To demonstrate that this deposition scheme preserves the desirable attributes of 2D COFs, spray-coated 2D COF thin films are incorporated as the active material in acoustic sensors. These 2D-COF-based sensors have a 10 ppb limit-of-quantification for trimethylamine, which places them among the most sensitive sensors for meat and seafood spoilage. Overall, this work establishes a scalable additive manufacturing technique that enables the integration of 2D COFs into thin-film device architectures.
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Flanders NC, Kirschner MS, Kim P, Fauvell TJ, Evans AM, Helweh W, Spencer AP, Schaller RD, Dichtel WR, Chen LX. Large Exciton Diffusion Coefficients in Two-Dimensional Covalent Organic Frameworks with Different Domain Sizes Revealed by Ultrafast Exciton Dynamics. J Am Chem Soc 2020; 142:14957-14965. [PMID: 32657123 DOI: 10.1021/jacs.0c05404] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Large singlet exciton diffusion lengths are a hallmark of high performance in organic-based devices such as photovoltaics, chemical sensors, and photodetectors. In this study, exciton dynamics of a two-dimensional covalent organic framework, 2D COF-5, is investigated using ultrafast spectroscopic techniques. After photoexcitation, the COF-5 exciton decays via three pathways: (1) excimer formation (4 ± 2 ps), (2) excimer relaxation (160 ± 40 ps), and (3) excimer decay (>3 ns). Excitation fluence-dependent transient absorption studies suggest that COF-5 has a relatively large diffusion coefficient (0.08 cm2/s). Furthermore, exciton-exciton annihilation processes are characterized as a function of COF-5 crystallite domain size in four different samples, which reveal domain-size-dependent exciton diffusion kinetics. These results reveal that exciton diffusion in COF-5 is constrained by its crystalline domain size. These insights indicate the outstanding promise of delocalized excitonic processes available in 2D COFs, which motivate their continued design and implementation into optoelectronic devices.
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Persson R, Lee S, Yood MU, Wagner MR, Minton N, Niemcryk S, Lindholm A, Evans AM, Jick S. Incident depression in patients diagnosed with multiple sclerosis: a multi-database study. Eur J Neurol 2020; 27:1556-1560. [PMID: 32397001 DOI: 10.1111/ene.14314] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 04/26/2020] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND PURPOSE Data on rates of newly diagnosed depression after multiple sclerosis (MS) diagnosis are sparse. Here, incident, treated depression in MS patients after diagnosis compared with matched non-MS patients is described. METHODS A matched cohort study was conducted in two separate electronic medical databases: the US Department of Defense (US-DOD) military healthcare system and the UK's Clinical Practice Research Datalink GOLD (UK-CPRD). The study population included all patients with a first recorded diagnosis of MS and matched non-MS patients. Patients with a history of treated depression were excluded. Incidence rates and incidence rate ratios with 95% confidence intervals for treated depression after MS diagnosis/matched date were estimated. RESULTS Incidence rate ratios of treated depression amongst MS patients compared with non-MS patients were 3.20 (95% confidence interval 3.05-3.35) in the US-DOD and 1.90 (95% confidence interval 1.74-2.06) in the UK-CPRD. Incidence rate ratios were elevated across age and sex. Rates were higher in females than males but, compared to non-MS patients, males with MS had a higher relative risk than females with MS. CONCLUSIONS Multiple sclerosis patients in the UK and the USA have a two- to three-fold increased risk of new, treated depression compared to matched non-MS patients.
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Ratsch M, Ye C, Yang Y, Zhang A, Evans AM, Börjesson K. All-Carbon-Linked Continuous Three-Dimensional Porous Aromatic Framework Films with Nanometer-Precise Controllable Thickness. J Am Chem Soc 2020; 142:6548-6553. [PMID: 32186875 PMCID: PMC7309314 DOI: 10.1021/jacs.9b10884] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
![]()
Inherently porous materials that
are chemically and structurally
robust are challenging to construct. Conventionally, dynamic chemistry
is thought to be needed for the formation of uniform porous organic
frameworks, but dynamic bonds can limit the stability of these materials.
For this reason, all-carbon-linked frameworks are expected to exhibit
higher stability performance than more traditional porous frameworks.
However, the limited reversibility of carbon–carbon bond-forming
reactions has restricted the exploration of these materials. In particular,
the challenges associated with producing uniform thin films of all-carbon-linked
frameworks has inhibited the study of these materials in applications
where well-defined films are required. Here, we synthesize continuous
and homogeneous films of two different all-carbon-linked three-dimensional
porous aromatic frameworks with nanometer-precision thickness (PAF-1
and BCMP-2). This was accomplished by kinetically promoting surface
reactivity while suppressing homogeneous nucleation. Through connection
of the PAF film to a gold substrate via a self-assembled monolayer
and use of flow conditions to continually introduce monomers, smooth
and continuous PAF films can be grown with controlled thickness. This
strategy allows traditional transition metal mediated carbon–carbon
cross-coupling reactions to form porous, organic thin films. We expect
that the chemical principles uncovered in this study will enable the
synthesis of a variety of chemically and structurally diverse carbon–carbon-linked
frameworks as high-quality films, which are inaccessible by conventional
methods.
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Burke DW, Sun C, Castano I, Flanders NC, Evans AM, Vitaku E, McLeod DC, Lambeth RH, Chen LX, Gianneschi NC, Dichtel WR. Acid Exfoliation of Imine‐linked Covalent Organic Frameworks Enables Solution Processing into Crystalline Thin Films. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201913975] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Burke DW, Sun C, Castano I, Flanders NC, Evans AM, Vitaku E, McLeod DC, Lambeth RH, Chen LX, Gianneschi NC, Dichtel WR. Acid Exfoliation of Imine‐linked Covalent Organic Frameworks Enables Solution Processing into Crystalline Thin Films. Angew Chem Int Ed Engl 2020; 59:5165-5171. [DOI: 10.1002/anie.201913975] [Citation(s) in RCA: 84] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Indexed: 11/08/2022]
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Persson R, Lee S, Ulcickas Yood M, Wagner Usn Mc CM, Minton N, Niemcryk S, Lindholm A, Evans AM, Jick SS. Infections in patients diagnosed with multiple sclerosis: A multi-database study. Mult Scler Relat Disord 2020; 41:101982. [PMID: 32070858 DOI: 10.1016/j.msard.2020.101982] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 12/23/2019] [Accepted: 02/03/2020] [Indexed: 11/16/2022]
Abstract
BACKGROUND Recent data on the rates of infections among patients with multiple sclerosis (MS) are sparse. The objective of this study was to quantify incidence of infections in patients with MS compared with a matched sample of patients without MS (non-MS). METHODS This study was conducted in two separate electronic medical databases: the United States Department of Defense (US-DOD) military health care system and the United Kingdom's Clinical Practice Research Datalink GOLD (UK-CPRD). We identified patients with a first recorded diagnosis of MS between 2001 and 2016 (UK-CPRD) or 2004 and 2017 (US-DOD) and matched non-MS patients. We identified infections recorded after the MS diagnosis date (or the matched date in non-MS patients) and calculated incidence rates (IRs) and incidence rate ratios (IRRs) with 95% confidence intervals (CIs) by infection site and type. RESULTS Relative to non-MS patients, MS patients had higher rates of any infection (US-DOD IRR 1.76; 95% CI 1.72-1.80 and UK-CPRD IRR 1.25; 95% CI 1.21-1.29) and a two-fold higher rate of hospitalized infections (US-DOD IRR 2.43; 95% CI 2.23-2.63 and UK-CPRD IRR 2.00; 95% CI 1.84-2.17). IRs of any infection were higher in females compared with males in both MS and non-MS patients, while IRs of hospitalized infections were similar between sexes in both MS and non-MS patients. The IR of first urinary tract or kidney infection was nearly two-fold higher in MS compared with non-MS patients (US-DOD IRR 1.88; 95% CI 1.81-1.95 and UK-CPRD IRR 1.97; 95% CI 1.86-2.09) with higher rates in females compared with males. IRs for any opportunistic infection, candidiasis and any herpes virus were increased between 20 and 52% among MS patients compared with non-MS patients. IRs of meningitis, tuberculosis, hepatitis B and C were all low. CONCLUSION MS patients have an increased risk of infection, notably infections of the renal tract, and a two-fold increased risk of hospitalized infections compared with non-MS patients.
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Strauss MJ, Evans AM, Castano I, Li RL, Dichtel WR. Supramolecular polymerization provides non-equilibrium product distributions of imine-linked macrocycles. Chem Sci 2020; 11:1957-1963. [PMID: 34123290 PMCID: PMC8148301 DOI: 10.1039/c9sc05422g] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Supramolecular polymerization of imine-linked macrocycles has been coupled to dynamic imine bond exchange within a series of macrocycles and oligomers. In this way, macrocycle synthesis is driven by supramolecular assembly, either into small aggregates supported by π–π interactions, or high-aspect ratio nanotubes stabilized primarily by electrostatic and solvophobic interactions. For the latter, supramolecular polymerization into nanotubes restricts imine exchange, thereby conferring chemical stability to the assemblies and their constituent macrocycles. Competition in the formation and component exchange among macrocycles favored pyridine-2,6-diimine-linked species due to their rapid synthesis, thermodynamic stability, and assembly into high-aspect ratio nanotubes under the reaction conditions. In addition, the pyridine-containing nanotubes inhibit the formation of similar macrocycles containing benzene-1,3-diimine-linkages, presumably by disrupting their assembly and templation. Finally, we exploit rapid imine exchange within weak, low-aspect ratio macrocycle aggregates to carry out monomer exchange reactions to macrocycles bearing pyridine moieties. Once a pyridine-containing dialdehyde has exchanged into a macrocycle, the macrocycle becomes capable of nanotube formation, which dramatically slows further imine exchange. This kinetic trap provides chemically diverse macrocycles that are not attainable by direct synthetic methods. Together these findings provide new insights into coupling supramolecular polymerization and dynamic covalent bond-forming processes and leverages this insight to target asymmetric nanotubes. We envision these findings spurring further research efforts in the synthesis of nanostructures with designed and emergent properties. Supramolecular polymerization of imine-linked macrocycles has been coupled to dynamic imine bond exchange within a series of macrocycles and oligomers.![]()
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Li H, Evans AM, Castano I, Strauss MJ, Dichtel WR, Bredas JL. Nucleation-Elongation Dynamics of Two-Dimensional Covalent Organic Frameworks. J Am Chem Soc 2020; 142:1367-1374. [PMID: 31867961 DOI: 10.1021/jacs.9b10869] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Homogeneous two-dimensional (2D) polymerization is a poorly understood process in which topologically planar monomers react to form planar macromolecules, often termed 2D covalent organic frameworks (COFs). While these COFs have traditionally been limited to weakly crystalline aggregated powders, they were recently grown as micron-sized single crystals by temporally resolving the growth and nucleation processes. Here, we present a quantitative analysis of the nucleation and growth rates of 2D COFs via kinetic Monte Carlo (KMC) simulations using COF-5 as an example, which show that nucleation and growth have second-order and first-order dependences on monomer concentration, respectively. The computational results were confirmed experimentally by systematic measurements of COF nucleation and growth rates performed via in situ X-ray scattering, which validated the respective monomer concentration dependencies of the nucleation and elongation processes. A major consequence is that there exists a threshold monomer concentration below which growth dominates over nucleation. Our computational and experimental findings rationalize recent empirical observations that, in the formation of 2D COF single crystals, growth dominates over nucleation when monomers are added slowly, so as to limit their concentrations. This mechanistic understanding of the nucleation and growth processes will inform the rational control of polymerization in two dimensions and ultimately enable access to high-quality samples of designed two-dimensional polymers.
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Jhulki S, Evans AM, Hao XL, Cooper MW, Feriante CH, Leisen J, Li H, Lam D, Hersam MC, Barlow S, Brédas JL, Dichtel WR, Marder SR. Humidity Sensing through Reversible Isomerization of a Covalent Organic Framework. J Am Chem Soc 2020; 142:783-791. [DOI: 10.1021/jacs.9b08628] [Citation(s) in RCA: 104] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Feriante CH, Jhulki S, Evans AM, Dasari RR, Slicker K, Dichtel WR, Marder SR. Rapid Synthesis of High Surface Area Imine-Linked 2D Covalent Organic Frameworks by Avoiding Pore Collapse During Isolation. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1905776. [PMID: 31763734 DOI: 10.1002/adma.201905776] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 10/31/2019] [Indexed: 05/09/2023]
Abstract
Imine-linked 2D covalent organic frameworks (COFs) form more rapidly than previously reported under Brønsted acid-catalyzed conditions, showing signs of crystallinity within a few minutes, and maximum crystallinity within hours. These observations contrast with the multiday reaction times typically employed under these conditions. In addition, vacuum activation, which is often used to isolate COF materials significantly erodes the crystallinity and surface area of the several isolated materials, as measured by N2 sorption and X-ray diffraction. This loss of material quality during isolation for many networks has historically obscured otherwise effective polymerization conditions. The influence of the activation procedure is characterized in detail for three COFs, with the commonly used 1,3,5-tris(4-aminophenyl)benzene-terephthaldehyde network (TAPB-PDA COF), the most prone to pore collapse. When the networks are activated carefully, rapid COF formation is general for all five of the imine-linked 2D COFs studied, with all exhibiting excellent crystallinity and surface areas, including the highest surface areas reported to date for three materials. Furthermore, to simplify the workup of COF materials, a simple nitrogen flow method provides high-quality materials without the need for specialized equipment. These insights have important implications for studying and understanding how 2D COFs form.
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Castano I, Evans AM, Li H, Vitaku E, Strauss MJ, Brédas JL, Gianneschi NC, Dichtel WR. Chemical Control over Nucleation and Anisotropic Growth of Two-Dimensional Covalent Organic Frameworks. ACS CENTRAL SCIENCE 2019; 5:1892-1899. [PMID: 31807691 PMCID: PMC6891846 DOI: 10.1021/acscentsci.9b00944] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Indexed: 05/19/2023]
Abstract
Two-dimensional covalent organic frameworks (2D COFs) are composed of structurally precise, permanently porous, layered polymer sheets. 2D COFs have traditionally been synthesized as polycrystalline aggregates with small crystalline domains. Only recently have a small number of 2D COFs been obtained as single crystals, which were prepared by a seeded growth approach via the slow introduction of monomers, which favored particle growth over nucleation. However, these procedures are slow and operationally difficult, making it desirable to develop polymerization methods that do not require the continuous addition of reactants over days or weeks. Here, we achieve the rapid growth of boronate ester-linked COFs by chemically suppressing nucleation via addition of an excess of a monofunctional competitor, 4-tert-butylcatechol (TCAT), into the polymerization. In situ X-ray scattering measurements show that TCAT suppresses colloid nucleation, which enables seeded growth polymerizations in the presence of high monomer concentrations. Kinetic Monte Carlo simulations reveal that TCAT limits oligomers to sizes below the critical nucleus size and that in-plane expansion is restricted compared to out-of-plane oriented attachment of oligomers. The simulations are consistent with transmission electron micrographs, which show that the particles grow predominantly in the stacking direction. This mechanistic insight into the role of the modulators in 2D polymerizations enables the size and aspect ratio of COF colloids to be controlled under operationally simple conditions. This chemically controlled growth strategy will accelerate the discovery and exploration of COF materials and their emergent properties.
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Evans AM, Castano I, Brumberg A, Parent LR, Corcos AR, Li RL, Flanders NC, Gosztola DJ, Gianneschi NC, Schaller RD, Dichtel WR. Emissive Single-Crystalline Boroxine-Linked Colloidal Covalent Organic Frameworks. J Am Chem Soc 2019; 141:19728-19735. [DOI: 10.1021/jacs.9b08815] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Strauss MJ, Asheghali D, Evans AM, Li RL, Chavez AD, Sun C, Becker ML, Dichtel WR. Cooperative Self‐Assembly of Pyridine‐2,6‐Diimine‐Linked Macrocycles into Mechanically Robust Nanotubes. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201907668] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Strauss MJ, Asheghali D, Evans AM, Li RL, Chavez AD, Sun C, Becker ML, Dichtel WR. Cooperative Self‐Assembly of Pyridine‐2,6‐Diimine‐Linked Macrocycles into Mechanically Robust Nanotubes. Angew Chem Int Ed Engl 2019; 58:14708-14714. [DOI: 10.1002/anie.201907668] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 07/26/2019] [Indexed: 11/06/2022]
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Evans AM, Ryder MR, Flanders NC, Vitaku E, Chen LX, Dichtel WR. Buckling of Two-Dimensional Covalent Organic Frameworks under Thermal Stress. Ind Eng Chem Res 2019. [DOI: 10.1021/acs.iecr.9b01288] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Zhukhovitskiy AV, Kobylianskii IJ, Thomas AA, Evans AM, Delaney CP, Flanders NC, Denmark SE, Dichtel WR, Toste FD. A Dinuclear Mechanism Implicated in Controlled Carbene Polymerization. J Am Chem Soc 2019; 141:6473-6478. [PMID: 30964670 PMCID: PMC6615555 DOI: 10.1021/jacs.9b01532] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Carbene polymerization provides polyolefins that cannot be readily prepared from olefin monomers; however, controlled and living carbene polymerization has been a long-standing challenge. Here we report a new class of initiators, (π-allyl)palladium carboxylate dimers, which polymerize ethyl diazoacetate, a carbene precursor in a controlled and quasi-living manner, with nearly quantitative yields, degrees of polymerization >100, molecular weight dispersities 1.2-1.4, and well-defined, diversifiable chain ends. This method also provides block copolycarbenes that undergo microphase segregation. Experimental and theoretical mechanistic analysis supports a new dinuclear mechanism for this process.
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Li RL, Flanders NC, Evans AM, Ji W, Castano I, Chen LX, Gianneschi NC, Dichtel WR. Controlled growth of imine-linked two-dimensional covalent organic framework nanoparticles. Chem Sci 2019; 10:3796-3801. [PMID: 30996969 PMCID: PMC6446964 DOI: 10.1039/c9sc00289h] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 02/20/2019] [Indexed: 11/30/2022] Open
Abstract
Covalent organic frameworks (COFs) consist of monomers arranged in predictable structures with emergent properties. However, improved crystallinity, porosity, and solution processability remain major challenges. To this end, colloidal COF nanoparticles are useful for mechanistic studies of nucleation and growth and enable advanced spectroscopy and solution processing of thin films. Here we present a general approach to synthesize imine-linked 2D COF nanoparticles and control their size by favoring imine polymerization while preventing the nucleation of new particles. The method yields uniform, crystalline, and high-surface-area particles and is applicable to several imine-linked COFs. In situ X-ray scattering experiments reveal the nucleation of amorphous polymers, which crystallize via imine exchange processes during and after particle growth, consistent with previous mechanistic studies of imine-linked COF powders. The separation of particle formation and growth processes offers control of particle size and may enable further improvements in crystallinity in the future.
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Daugherty MC, Vitaku E, Li RL, Evans AM, Chavez AD, Dichtel WR. Improved synthesis of β-ketoenamine-linked covalent organic frameworks via monomer exchange reactions. Chem Commun (Camb) 2019; 55:2680-2683. [DOI: 10.1039/c8cc08957d] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
β-Ketoenamine-linked COFs with improved crystallinity are achieved through monomer exchange of isostructural imine-linked COFs.
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