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Encapsulation of liquid guest molecules in hydrogen-bonded frameworks permits analysis of their preferred conformations through single crystal X-ray diffraction. 

Crystalline fibers of the hydrogen-bonded framework bis(guanidinium) naphthalene-1,5-disulfonate, (G)2(1,5-NDS), with ethanol guest molecules twist as they grow when deposited from solution under conditions that favor low nucleation densities and high branching rates. Spherulites comprising helicoidal fibers with a pitch of 3.4 ± 0.5 μm display rhythmic concentric variations in interference colors between crossed polarizers. Tightly packed fibers and platelets, systematically change orientations between flat-on and edge-on crystallites with respect to the substrate surface. Mueller matrix imaging reveals periodic oscillations in the absolute magnitude of the linear retardance and an associated bisignate circular retardance. Single-crystal X-ray diffraction data demonstrates that the twisted (G)2(1,5-NDS)⊃EtOH crystals adopt a bilayer packing motif with ethanol as guest molecules (space group P1 ̅). When the banded spherulite films were subsequently heated at 130°C, the solvated phase was converted to a guest-free crystalline phase (space group P21/c). This transition resulted in loss of linear retardance. 

Hydrogen-bonded frameworks (HBFs) have been studied for decades owing to their fascinating and diverse architectures, always with an eye toward the role of hydrogen bonding in their design as well as their utility in various applications. This review addresses recent advances in HBFs that illustrate their versatility and utility stemming from their unique attributes compared with other classes of molecular frameworks. Guanidinium organosulfonate hydrogen-bonded frameworks, pioneered in our lab and one of the most extensive and versatile collections of HBFs, are used to illustrate molecular design concepts and the principle of architectural isomerism that expands access to a greater structural landscape. Recognizing the growing role of computation in materials design, from ab initio methods to machine learning, this review also touches on their emerging use in the design and synthesis of HBFs. The growth of the HBF arsenal promises continuing innovations, with applications ranging from electronic materials and chemical separations to gas adsorption and catalysis.