Postsynthetic Metalation of a Robust Hydrogen-Bonded Organic Framework for Heterogeneous Catalysis

Abstract

Hydrogen-bonded organic framework (HOF)-based catalysts still remain unreported thus far due to their relatively weak stability. In the present work, a robust porous HOF (HOF-19) with a Brunauer–Emmett–Teller surface area of 685 m2 g–1 was reticulated from a cagelike building block, amino-substituted bis­(tetraoxacalix[2]­arene[2]­triazine), depending on the hydrogen bonding with the help of π–π interactions. The postsynthetic metalation of HOF-19 with palladium acetate afforded a palladium­(II)-containing heterogeneous catalyst with porous hydrogen-bonded structure retained, which exhibits excellent catalytic performance for the Suzuki–Miyaura coupling reaction with the high isolation yields (96–98%), prominent stability, and good selectivity. More importantly, by simple recrystallization, the catalytic activity of deactivated species can be recovered from the isolation yield 46% to 92% for 4-bromobenzonitrile conversion at the same conditions, revealing the great application potentials of HOF-based catalysts.

The Chemistry of Porous Organic Molecular Materials

“…Diamino triazine units were used by Wuest to construct a stable hydrogen-bondedorganic framework (HOF), [97] later referred to as HOF-1 by Chen et al, [98] and this concept has been extended to a series of rigid, organic scaffolds to prepare open hydrogen bonded structures. [83,[102][103][104][105][106][107][108][109][110][111][112][113][114][115][116] However, even for these directional diamino triazine based HOF structures, it has not been possible to develop reticular chemistry concepts that are comparable to those developed in MOF and COF syntheses. [46,48,[52][53][54][55] This creates a fundamental materials design challenge, since it is not in general possible to functionalize a porous organic molecular material without, probably, making a significant change to the crystal packing and hence the porous properties.…”

“…Interestingly, an amino-substituted bis(tetraoxacalix [2]arene [2]triazine), with the same symmetry as T2, crystallized to form the porous HOF-19, which is isostructural with T2-β. [108] Also, an imidazole functionalized triptycene (H3TBI) was reported to crystallize as a distorted porous structural analogue of T2-γ. [277] There are some similarities between the use of ESF maps in materials discovery and the high-throughput screening of hypothetical MOFs structures for useful functions.…”

Self-Recognizing π-π Stacking Interactions Designed for the Generation of Ultrastable Mesoporous Hydrogen-Bonded Organic Frameworks

“…Recently, hydrogen-bonded organic frameworks (HOFs), [1][2][3][4] self-assembled from pre-designed molecular tectons using intermolecular H-bonding interactions, are rapidly expanding into a library of novel functional crystalline porous materials with diverse structures and applications including gas storage and separation, 5,6 chiral separation, 7 chemical sensing, 8 proton conduction, 9 and catalysis. 10,11 However, since the first report of HOF materials with permanent microporosity about a decade ago, 12 the development of HOFs has been hindered due to poor stability as a result of the weak H-bonding nature. Alternatively, various synthetic porous solids such as silicates, 13 carbons, 14 MOFs, 15 and COFs 16 have achieved a wide range of pore sizes from micro-to mesopores.…”

Self-Recognizing π-π Stacking Interactions Designed for the Generation of Ultrastable Mesoporous Hydrogen-Bonded Organic Frameworks

“…Recently, hydrogen-bonded organic frameworks (HOFs), [1][2][3][4] self-assembled from pre-designed molecular tectons using intermolecular H-bonding interactions, are rapidly expanding into a library of novel functional crystalline porous materials with diverse structures and applications including gas storage and separation, 5,6 chiral separation, 7 chemical sensing, 8 proton conduction, 9 and catalysis. 10,11 However, since the first report of HOF materials with permanent microporosity about a decade ago, 12 the development of HOFs has been hindered due to poor stability as a result of the weak H-bonding nature. Alternatively, various synthetic porous solids such as silicates, 13 carbons, 14 MOFs, 15 and COFs 16 have achieved a wide range of pore sizes from micro-to mesopores.…”