  Quantum spin liquids are an exciting playground for exotic physical phenomena
and emergent many-body quantum states. The realization and discovery of quantum
spin liquid candidate materials and associated phenomena lie at the
intersection of solid-state chemistry, condensed matter physics and materials
science and engineering. In this review, we provide the current status of the
crystal chemistry, synthetic techniques, physical properties, and research
methods in the field of quantum spin liquids. We also highlight a number of
specific quantum spin liquid candidate materials and their structure-property
relationships, elucidating their fascinating behavior and connecting it to the
intricacies of their structures. Furthermore, we share our thoughts on defects
and their inevitable presence in materials, of which quantum spin liquids are
no exception, which can complicate the interpretation of characterization of
these materials, and urge the community to extend their attention to materials
preparation and data analysis, cognizant of the impact of defects. This review
was written with the intention of providing guidance on improving the materials
design and growth of quantum spin liquids, and painting a picture of the beauty
of the underlying chemistry of this exciting class of materials.
