Crystal engineering of molecular materials is commonly frustrated by the absence of reliable structural paradigms that are needed for systematic design of crystal lattices with predictable structure and desirable function. This problem can be attributed, at least partially, to the absence of robust supramolecular motifs that serve as synthons for the assembly of crystal lattices. A novel class of molecular crystals based on two-dimensional hydrogen (H)-bonded networks comprising guanidinium ions and the sulfonate groups of alkane- or arenedisulfonate ions is described. The disulfonate ions act as pillars that connect opposing H-bonded sheets and form nanoporous galleries with one-dimensional channels. The flexibility of the H-bonded network allows the galleries to adapt to changes in the steric requirements of guest molecules that occupy the channels. This robustness reduces crystal engineering to the last remaining dimension, enabling rational adjustment of the gallery heights by choice of the disulfonate pillar.

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Molecular crystals constructed by hydrogen bonding can be viewed as having nanostructural elements consisting of ordered, supramolecular hydrogen-bonded networks. These networks, whose dimensionalities and motifs are governed by the molecular structure and hydrogen-bonding topology of their constituents, can serve as “modules” in the design and synthesis of molecular materials. Robust supramolecular modules can reduce significantly the number of possible solid-state packing motifs, a key goal of crystal engineering strategies which aim to design and synthesize molecular solids with controlled solid-state structure and properties. Several examples of hydrogen bonded modules in molecular crystals are described, including one-dimensional hydrogen-bonded wires, two-dimensional hydrogen-bonded layers, and nanoporous hydrogen-bonded lattices with voids having differing dimensionalities. The presence of reliable modules in these materials provides for a better general understanding of the organization principles governing molecular and solid-state assembly by reducing the number of variables in systematic studies.