Self-Assembly of Catalytically Active Supramolecular Coordination Compounds within Metal–Organic Frameworks

Abstract

Supramolecular Coordination Compounds (SCCs) represent the power of Coordination Chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesised in solution, with isolated fully-coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-Organic Frameworks (MOFs) show unique features to act as chemical nanoreactors for the in-situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of Pd II SCCs within the confined space of a preformed MOF (SCCs@MOF) and its post-assembly metalation to give a Pd II -Au III supramolecular assembly, crystallography underpinned. These SCCs@MOF catalyse the coupling of boronic acids and/or alkynes, representative multisite metallic-catalysed reactions in which traditional SCCs tend to decompose, and retain its structural integrity as consequence of the synergetic hybridization between SCCs and MOF. These results open new avenues in both the synthesis of novel SCCs and their use on heterogeneous metal-based Supramolecular Catalysis.

Confining isolated atoms and clusters in crystalline porous materials for catalysis

“…The unique reactivity of confined Pd4 clusters can be ascribed to its metastable mixed-valence 0/+1 oxidation state. Another application of Pd clusters (with different atomicity) confined in MOF have been reported for catalysing the homocoupling of thienylboronic acids and terminal alkynes 198 .…”

Metal–Organic Frameworks as Chemical Nanoreactors: Synthesis and Stabilization of Catalytically Active Metal Species in Confined Spaces

“…Applying this approach, we recently reported the preparation of two mechanically-bonded insitu self-assembled catalytically-active SCCs@MOFs. 55 Starting from the anionic 2a), the first PS step consisted of replacing Ni 2+ cations hosted in the pores (Figure 2a) by Pd 2+ ones (Figure 10). organic polygon when using the linear ligand L1 (Figure 10), whereas a Pd II 16 supramolecular assembly (Pd II 16@MOF) with the tripodal bended ligand L2 (Figure 10), were observed.…”

MOF-enabled confinement and related effects for chemical catalyst presentation and utilization

“…In this section, we will discuss the four most common approaches to noncovalent encapsulation and presentation of molecular catalysts or co-catalysts by MOF pores: (a) ion-exchange of a charged catalyst into a framework of fixed complementary charge, (b) transient removal of a linker, typically with restoration after molecular-guest incorporation, (c) ship-in-a-bottle construction of a pore-filling metal complex or other guest from components that enter the pore via apertures that are narrower than the pore itself, and (d) simple size-matching of host and guest, together with London dispersion, hydrogen-bonding, pi-pi stacking, or other van der Waals interactions. [183][184][185][186][187][188] Note that the first and second approaches at least nominally require the presence of solvent, although the amount can be almost vanishingly small if incorporation relies upon mechanochemistry. [189][190][191] An example of case (a) is Weller, Rosseinsky, and co-workers' conversion of the well-known MOF, MIL-101 (Cr) to anionic form (as a sodium salt) by appending sulfonate groups to BDC 2À linkers, followed by partial exchange (B7%) of Ir(COD)(PCy 3 )(py) + (''Crabtree's catalyst''; COD = 1,5-cyclooctadiene; PCy 3 = tri-cyclohexyl-phosphine) 192 for Na + (Fig.…”