An Adaptive Hydrogen‐Bonded Organic Framework for the Exclusive Recognition of p‐Xylene

Abstract

Separation of xylene isomers is one of the most important but most challenging and energy‐intensive separation processes in the petrochemical industry. Here, we report an adaptive hydrogen‐bonded organic framework (HOF‐29) constructed from a porphyrin based organic building block 4,4′,4′′,4′′′‐(porphyrin‐5,10,15,20‐tetrayl) tetrabenzonitrile (PTTBN), exhibiting the exclusive molecular recognition of p‐xylene (pX) over its isomers of o‐xylene (oX) and m‐xylene (mX), as clearly demonstrated in the single crystal structure transformation and 1H NMR studies. Single crystal structure studies show that single‐crystal‐to‐single‐crystal transformation from the as‐synthesized HOF‐29 to the pX exclusively included HOF‐29⊃pX is triggered by the encapsulation of pX molecules, accompanied by sliding of the 2D layers and local distortion of the ligand, which provides multiple C−H⋅⋅⋅π interactions.

Solvent-Dependent Self-Assembly of Hydrogen-Bonded Organic Porphyrinic Frameworks

“…Such binding fashion and stacking pattern in HOF-26 is similar to those observed in our previously published HOF-29⊃pX but with a slightly larger cavity size to accommodate the bulkier EB molecule. 44 HOF-27 crystallizes in the triclinic space group P1̅ , with one crystallographically unique PTTBN molecule and two different NB molecules in the asymmetric unit. Compared to HOF-26, although the sql topology and the number of hydrogen bonding interactions are unaltered, the connectivity of the PTTBN linker observed in HOF-27 is slightly different: all four pyrrole subunits in the PTTBN are hydrogen-bonded to the neighboring linkers (C−H•••N 3.434−3.532 Å), which gives rise to a distorted sql network (interior angle from 62.9°i n HOF-26 to 87.4°in HOF-27) and a round-shaped cavity with a size of 12.2 × 11.0 Å 2 (Figures 2a and S6b).…”

“…The organic linker 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrabenzonitrile (PTTBN) was synthesized according to our previous work. 44 The gas sorption measurements were carried out on an automatic volumetric adsorption apparatus Micromeritics ASAP 2020 surface area analyzer. Prior to the gas sorption analyses, the samples were activated under a dynamic vacuum at 100 °C for 3 h.…”

“…33,42,43 Recently, we demonstrated unprecedented ethylene/ethane separation performance and exclusive p-xylene molecular recognition from C8 mixtures in benzonitrile-based HOFs. 44,45 Motivated by these works, we further explored the self-assembly of benzonitrile-based porphyrinic organic linkers in different solvent systems (polar and nonpolar) to gain more insight into the self-assembly mechanism of HOF chemistry. Herein, we report three HOFs, HOF-26, HOF-27, and HOF-28, assembled by a porphyrinic organic linker 4,4′,4″,4‴- employed, which led to distinct pore space and geometries.…”

An anthracene-based hydrogen-bonded organic framework as a bifunctional fluorescent sensor for the detection of γ-aminobutyric acid and nitrofurazone

“…[42][43][44][45][46][47] Moreover, HOFs can be highly crystallized, which facilitates structure determination and the investigation of the structure-property relationship. In recent years, HOFs, as a new type of porous framework material, have been explored in gas separation, [48][49][50] catalysis, [51][52][53] gas storage, [54][55][56][57] fluorescence detection [58][59][60][61][62][63][64][65] and enzyme encapsulation. 66 Furthermore, the metal-free nature endows HOFs with considerable biocompatibility and low toxicity; thus HOFs could be an excellent candidate for the detection of drugs and biomarkers.…”

“…42–47 Moreover, HOFs can be highly crystallized, which facilitates structure determination and the investigation of the structure–property relationship. In recent years, HOFs, as a new type of porous framework material, have been explored in gas separation, 48–50 catalysis, 51–53 gas storage, 54–57 fluorescence detection 58–65 and enzyme encapsulation. 66…”