Hierarchical Assembly of a Micro‐ and Macroporous Hydrogen‐Bonded Organic Framework with Tailored Single‐Crystal Size

Abstract Porous organic molecular materials represent an emergent field of research in Chemistry and Materials Science due to their unique combination of properties. To enhance their performance and expand the number of applications, the incorporation of hierarchical porosity is required, as exclusive microporosity entails several limitations. However, the integration of macropores in porous organic molecular materials is still an outstanding challenge. Herein, we report the first example of a hydrogen‐bonded organic framework (MM‐TPY) with hierarchical skeletal morphology, containing stable micro‐ and macroporosity. The crystal size, from micro to centimetre scale, can be controlled in a single step without using additives or templates. The mechanism of assembly during the crystal formation is compatible with a skeletal crystal growth. As proof of concept, we employed the hierarchical porosity as a platform for the dual, sequential and selective co‐recognition of molecular species and microparticles.

-Hierarchical tubular crystals (MM-TPY): TPY (10 mg) in toluene (15 mL) were added into a glass vial. The mixture was heated at 110 o C for 10 minutes until complete dissolution. After all the toluene was evaporated at room temperature, the hollow crystals of MM-TPY were collected. By controlling the evaporation rate of toluene from hours to days, crystals of micrometre or mm scale can be obtained.
-Study of the mechanism of formation of hierarchical tubular crystals (MM-TPY): a few drops of a solution of 10 mg of TPY in toluene (15 mL) was deposited on a glass slide and left to evaporate quickly at room temperature (~20 minutes), resulting in micrometre scale crystals.
-Study for the selective co-recognition of dyes and microparticles: 1-Dye mixture: millimetre size crystals of MM-TPY were dipped in a mixture of Methylene Blue (MB) and Phenol Red (PR) in acetone for 48 h and then filtered, washed and dried for the next step. 2-Microparticle mixture: a few drops of a suspension of activated carbon particles and silica gel particles in acetonitrile/water (9/1) were deposited on a glass slide containing crystals of PR@MM-TPY and left to complete evaporation. After the process was repeated 3 times, the crystals were gently washed with acetonitrile/water.  Table S1. Crystallographic data and structure refinement results of M-TPY crystallized in dichloromethane/ethanol mixture and face indexing.   software used to prepare material for publication: Bruker SHELXTL.
Computations were performed on six different structures to investigate the different types of interactions ( Figure S5). A stacked dimer, trimer, and tetramer were considered. In addition, a dimer containing a hydrogen bond (N...H-C) and a dimer showing side-on interlayer interactions were considered. Finally, a mixed tetramer containing all types of interactions was used. Computations indicate that the stacking energies are between 34 and 37.5 kcal/mol per dimer interaction. These numbers are robust with respect to changes in the model size and computational model. H-bonded interactions are significantly smaller (5.39 and 4.13 kcal/mol for M06-2X and wB97M-V); and side-on interactions are slightly smaller than these (4.54 and 3.02 kcal/mol for M06-2X and wB97M-V). Finally, the mixed dimer has an overall binding energy of 87.67 kcal/mol, which is consistent with its constituent interactions (2 x stacking, 2 x H-bond, 1 x side-on) adding up to 87.36 kcal/mol.

Stacked dimer H-bonded dimer
Stacked trimer

Side-on dimer
Stacked tetramer Mixed tetramer Figure S5. Dimer, trimer, and tetramer models used for the DFT computations. Table S2. Computed binding energies (kcal/mol) of the structures presented in Figure S5 using two different density functionals. Eb represents the overall interaction energy of the multimer, Eb' represents the binding energy per dimer. E_tot represents the calculated total energy