Accelerating Crystallization of Open Organic Materials by Poly(ionic liquid)s

Abstract The capability to significantly shorten the synthetic period of a broad spectrum of open organic materials presents an enticing prospect for materials processing and applications. Herein we discovered 1,2,4‐triazolium poly(ionic liquid)s (PILs) could serve as a universal additive to accelerate by at least one order of magnitude the growth rate of representative imine‐linked crystalline open organics, including organic cages, covalent organic frameworks (COFs), and macrocycles. This phenomenon results from the active C5‐protons in poly(1,2,4‐triazolium)s that catalyze the formation of imine bonds, and the simultaneous salting‐out effect (induced precipitation by decreasing solubility) that PILs exert on these crystallizing species.


Chemicals and Instrumentation
All chemicals were from commercial sources and used without further purification.
Transmission electron microscopy (TEM) was performed on a JEOL 2010FS transmission electron microscope operated at 120 kV. Powder X-ray diffraction (PXRD) was carried out on an X-ray diffractometer of Rigaku, Ultima IV. X-ray photoelectron spectroscopy (XPS) studies were performed on a ThermoFisher ESCALAB250 X-ray photoelectron spectrometer (powered at 150 W) using Al Kα radiation (λ = 8.357 Å). To compensate for surface charging effects, all XPS spectra were referenced to the C 1s neutral carbon peak at 284.6 eV. 1

H nuclear magnetic resonance ( 1 H-NMR) measurements
were carried out at room temperature on a Bruker DPX-400 spectrometer in different deuterated solvents.
The N2 sorption isotherms were measured on automatic volumetric adsorption equipment (Belsorp-mini II).

Synthesis of CC3R without Ptriaz additive:
The synthetic procedure used above to prepare CC3R-Ptriaz was followed without Ptriaz additive.

Synthesis of CC3R with PIL-imidaz additive:
The synthetic procedure used above to prepare CC3R-Ptriaz was followed by using PIL-imidaz containing chloroform instead of Ptriaz.

Synthesis of CC3R with PIL-py additive:
The synthetic procedure used above to prepare CC3R-Ptriaz was followed by using PIL-py containing chloroform instead of Ptriaz.

Synthesis of CC3R with triaz monomer additive:
The synthetic procedure used above to prepare CC3R-Ptriaz was followed by using triaz monomer containing chloroform instead of Ptriaz.

Synthesis of IPA-DACH macrocycle without Ptriaz additive:
The synthetic procedure used above to prepare IPA-DACH macrocycle without any additive.

Synthesis of catalyst for AB methanolysis reaction
Synthesis of Rh/CC3R-Ptriaz catalyst. In a typical synthesis, 4 mL of methanol containing 5 mg of CC3R (with Ptriaz additives, denoted as CC3R-Ptriaz) was subsequently added to 0.5 mL of methanol containing Rh(OAc)3 (0.01 mol Rh in content). The resultant mixture solution was further homogenized after aging for 20 min. Then, 0.5 mL of methanol solution containing 5 mg of NaBH4 was immediately added into the above solution with vigorous shaking, resulting in a well dispersion of Rh/CC3R-Ptriaz.
Synthesis of Rh/CC3R catalyst. The synthetic procedure used above to prepare Rh/CC3R-Ptriaz catalyst was followed by using 4 mL of methanol with as-synthesized CC3R as stabilizer.
Synthesis of Rh-SP-Free catalyst. The synthetic procedure used above to prepare Rh/CC3R-Ptriaz catalyst was followed by using 4 mL of methanol without any stabilizer.

Catalytic activity characterization
Procedure for the methanolysis of AB by Rh/CC3R-Ptriaz catalyst: The reaction apparatus for measuring the hydrogen evolution from the methanolysis of AB is as follows. In general, the assynthesized Rh/CC3R-Ptriaz catalyst was placed in a two-necked round-bottomed flask (30 mL), which was placed in a water bath under ambient atmosphere. A gas burette filled with water was connected to the reaction flask to measure the volume of hydrogen. The reaction started when AB (30.8 mg) in 0.8 mL of methanol was added into the flask. The volume of the evolved hydrogen gas was monitored by recording the displacement of water in the gas burette. The reaction was completed when there was no more gas generation. The methanolysis of AB can be expressed as follows:

Procedures for the methanolysis of AB by Rh-CC3R catalyst and Rh-SP-Free catalysts:
The procedures for the methanolysis of AB were similar to that of Rh/CC3R-Ptriaz catalyst except different catalysts were used.

Computational details for imine bond formation reaction
Density functional theory (DFT) calculations were carried out to understand the reaction mechanism between 1,2-Diaminocyclohexane and 1,3,5-Benzenetricarboxaldehyde in the presence of triazolium catalyst (the triazolium monomer was used for calculation) by using Gaussian 09 software package 1 .
Geometry optimization was carried out at the M062x method 2 with a 6-31+G(d,p) basis set 3 and in implicit solvent chloroform using PCM as solvation model 4 as implemented in Gaussian 09. The description of van der Waals interactions was improved using Grimme's empirical dispersion (GD3) correction 5 .
Frequency calculations, at the same level of theory, were used to obtain thermal corrections (at 298 K) and to characterize optimized structures as transition states (only a single imaginary frequency) or intermediate (if no imaginary frequencies were found). Single point energy calculations were performed at the M06-2x/Def2-TZVP level. 6 The Intrinsic reaction coordinate (IRC) 7 calculations of transition states were performed to confirm the appropriate connected reactants and products.

The interaction between 1,2-Diaminocyclohexane and triazolium ring
In the experiment, the up-field shift of the C5-proton signal was observed ( Figure S12) when mixing Ptriaz with 1,2-Diaminocyclohexane because of the hydrogen bonding (C5-H…N) interaction between -NH2 and triazolium moiety, which have been also revealed by theoretical calculation, an increase of C-H from 1.079 (triazolium) to 1.097 Å (triazolium + 1,2-Diaminocyclohexane) could be observed ( Figure   S32). Such strong interaction between 1,2-Diaminocyclohexane and Ptriaz favorably impair the strength of the C-H bond, leading to easier ionization of the C5-proton and enhancing acidity that catalyzes the imine bond formation reaction (as evidenced by in situ 1 H NMR spectra of CC3R formation process).