An Expandable Hydrogen-Bonded Organic Framework Characterized by Three-Dimensional Electron Diffraction

Abstract

A molecular crystal of a 2-D hydrogen-bonded organic framework (HOF) undergoes an unusual structural transformation after solvent removal from the crystal pores during activation. The conformationally flexible host molecule, ABTPA , adapts its molecular conformation during activation to initiate a framework expansion. The microcrystalline activated phase was characterized by three-dimensional electron diffraction (3D ED), which revealed that ABTPA uses out-of-plane anthracene units as adaptive structural anchors. These units change orientation to generate an expanded, lower density framework material in the activated structure. The porous HOF, ABTPA-2 , has robust dynamic porosity (SA BET = 1183 m 2 g –1 ) and exhibits negative area thermal expansion. We use crystal structure prediction (CSP) to understand the underlying energetics behind the structural transformation and discuss the challenges facing CSP for such flexible molecules.

An Ultrastable π–π Stacked Porous Organic Molecular Framework as a Crystalline Sponge for Rapid Molecular Structure Determination

“…There is a gate-opening action in the high relative pressure region (P/P 0 = 0.85), indicating that 1 is intrinsic flexibility (Figure 2b and Supporting Information Figure S4b). [47][48] The Brunauer-Emmett-Teller (BET) surface area is calculates as 150.6 m 2 •g -1 and the pore size distribution estimates by Horvath-Kawazoe cumulative pore volume plot is unimodal with a maximum peak at 5.7 Å (Supporting Information Figure S5), which is in excellent agreement with the diameter of the 1D nanopore observed in the structure. In addition, further research indicates that the activated 1 exhibits low adsorption capacity for light hydrocarbons at room temperature (Figure S6).…”

Single‐Atom Materials: Small Structures Determine Macroproperties

“…In addition to the low‐dimensional materials, the framework compounds (FCs) such as MOFs, [ 61 ] covalent organic frameworks (COFs), [ 62 ] and hydrogen‐bonded organic frameworks (HOFs), [ 63 ] are with ultrahigh surface areas, flexible constructing abilities, and well‐defined ordered structures, which make them very suitable candidates for the substrate of SAM. Based on these excellent properties, many FCs‐based SAM have been developed.…”

3D Electron Diffraction Structure Determination of Terrylene, a Promising Candidate for Intermolecular Singlet Fission

“… [9] In recent years, 3D ED has been extensively used for the structure determination of various nanocrystalline materials, ranging from inorganics to macromolecules. [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] In the world of small‐molecule organic compounds, 3D ED has been successfully employed for unveiling the structure of organic frameworks, [19] semiconductors [20] peptides,[ 21 , 22 ] pharmaceuticals[ 23 , 24 , 25 , 26 ] and natural products,[ 27 , 28 , 29 ] all of which could not be addressed by XRD methods.…”