Geometry Mismatch and Reticular Chemistry: Strategies To Assemble Metal–Organic Frameworks with Non-default Topologies

Abstract

The past 20 years have witnessed tremendous advances in the field of porous materials, including the development of novel metal-organic frameworks (MOFs) that show great potential for practical applications aimed at addressing global environmental and industrial challenges. A critical tool enabling this progress has been reticular chemistry, through which researchers can design materials that exhibit highly regular (i.e. edge-transitive) topologies, based on the assembly of geometrically-matched building blocks into specific nets. However, innovation sometimes demands that researchers steer away from default topologies to instead pursue unusual geometries. In this review, we cover this aspect and introduce the concept of geometry mismatch, in which seemingly incompatible building blocks are combined to generate non-default structures. We describe diverse MOF assemblies built through geometry mismatch generated by use of ligand bend-angles, twisted functional groups, zigzag ligands and other elements, focusing on carboxylate-based MOFs combined with common inorganic clusters. We aim to provide a fresh perspective on rational design of MOFs and to help readers understand the countless options now available to achieve greater structural complexity in MOFs.

Discovery of Zr-based metal-organic polygon: Unveiling new design opportunities in reticular chemistry

“…It seems that coplanarity is broken by the steric hindrance of the bulky functional group. Due to the sterically hindered functional group, the phenyl ring of a ligand is often rotated, referred as geometrical frustration [47]. The deliberate use of geometrically frustrated ligands allows the modification of the final topology of self-assembled cages [59,60].…”

“…The discovery of new building blocks can significantly affect the number of experimentally feasible metal-organic materials ( Fig. 1) [47].…”

Designer Metal–Organic Frameworks for Size‐Exclusion‐Based Hydrocarbon Separations: Progress and Challenges

“…[34] Furthermore, the application of reticular chemistry would allow us to tune the pore size of MOFs at sub-angstrom level, which is of particular importance to gain optimum separation efficiency. [35,36] The precise control of pore size could be realized through the design of ligands, as well as inorganic secondary building units (SBUs). [37,38] By applying these strategies, reticular chemistry has proven to be a powerful tool to guide the development of MOFs capable of full separation of molecules with dimensional differences less than 0.5 Å.…”

Synthesis of Polycarboxylate Rhodium(II) Metal–Organic Polyhedra (MOPs) and their use as Building Blocks for Highly Connected Metal–Organic Frameworks (MOFs)

“…We considered that 24‐c SBB geometry/connectivity is not compatible with square planar nodes (4‐c Cu paddle‐wheel clusters) to form a (4,24)‐c net, as the only binodal topology comprising 24‐c nodes of rhombicuboctahedra directionality is the edge‐transitive, (3,24)‐c rht net. It is known that, in presence of geometry mismatch, [26] certain clusters have tendency to undergo structural changes and form unprecedented clusters, including Cu II . Therefore, we confidently challenged the classical paddle‐wheel formation in the presence of our COOH‐RhMOP, aiming for the discovery of a novel 3‐c node comprising 3 carboxylates, distinct from the tetrazolate based trimer commonly used for the formation of rht ‐MOFs [11] .…”