Porous organic molecular solids by dynamic covalent scrambling

Abstract

The main strategy for constructing porous solids from discrete organic molecules is crystal engineering, which involves forming regular crystalline arrays. Here, we present a chemical approach for desymmetrizing organic cages by dynamic covalent scrambling reactions. This leads to molecules with a distribution of shapes which cannot pack effectively and, hence, do not crystallize, creating porosity in the amorphous solid. The porous properties can be fine tuned by varying the ratio of reagents in the scrambling reaction, and this allows the preparation of materials with high gas selectivities. The molecular engineering of porous amorphous solids complements crystal engineering strategies and may have advantages in some applications, for example, in the compatibilization of functionalities that do not readily cocrystallize.

Porous Organic Cage Thin Films and Molecular‐Sieving Membranes

“…CC13 was synthesized by reactions between 2-Methyl-1,2-propanediamine and 1,3,5-Triformylbenzene, followed by precipitation in petroleum ether, and further vacuum dried[5b]. Amorphous scrmabled porous organic cages (ASPOC) were synthesized by co-reaction of 1,3,5-triformylbenzene (TFB) with a mixture of both 1,2-ethylenediamine (EDA) and (1R,2R)-1,2-cyclohexanediamine (CHDA) leads to an equilibrium distribution of products incorporating both EDA-linked and CHDA-linked vertices in a single cage molecule [20]. RCC3 was synthesized by reducing CC3 with NaBH 4 in a mixture of chloroform and methanol [23].…”

“…For example, we have demonstrated amorphous scrambled porous organic cage molecules (ASPOC), synthesized using a mixture of different diamines, which leads to a distribution of cage species that cannot pack effectively, and therefore form amorphous solids rather than crystalline materials. [20] These molecules are also much more soluble in organic solvents, and can be used to fabricate 'porous liquids', [6] or used as a stabilizer for the dispersion of metal nanoparticle catalysts in solution.…”

“…To demonstrate the generality and transferability of this solution-processing approach, five different types of POCs were used to prepare thin films and membranes, including a representative crystalline cage CC3, [18] a related imine-cage, CC13, [5b] an amorphous scrambled porous organic cage mixture (ASPOC) synthesized by dynamic scrambling covalent reactions, [20] a reduced amine cage (RCC3), [23] and a 'tied' cage (FT-RCC3) by reaction of amine groups in RCC3 with carbonyls such as formaldehyde [23] that was shown previously to have exceptional stability to water, acids, and bases. More details of synthetic chemistry are given in Figure S1 in the Supporting Information.…”

Controlled thermal oxidative crosslinking of polymers of intrinsic microporosity towards tunable molecular sieve membranes

“…A typical plot of stress-strain curve (Fig. 2e) shows that the TOX-PIM-1 polymer films after slow crosslinking become stiff but are still mechanically robust in terms of tensile strength (50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60), elongation strain at break (in the range of 4-8%), and Young's modulus (1.2 to 1.7 Gpa) (Supplementary Fig. 7 and Supplementary Table 1).…”

“…Our approach on PIM-1 polymer represents a rational design and transformation of PIMs polymers, which is of broader fundamental significance to post-synthetic modification of the structure of channels and pores in a wide range of porous materials, such as MOFs 52 , porous organic molecules [53][54][55][56] , covalent organic frameworks 57 and graphenebased carbon materials [58][59][60] .…”