Advances in honeycomb layered oxides: Syntheses, layer stackings and material characterisation techniques of pnictogen- and chalcogen-based honeycomb layered oxides

Advancements in nanotechnology continue to unearth material vistas that presage a new age of revolutionary functionalities replete with unparalleled physical properties and avant-garde chemical capabilities that promise sweeping paradigm shifts in energy, environment, telecommunications and potentially healthcare. At the upper echelons of this realm, the pnictogen and chalcogen class of honeycomb layered oxides have emerged with fascinating crystal chemistry and exotic electromagnetic and topological phenomena that muster multifaceted concepts spanning from materials science to condensed matter physics and potential appli-cations in electrochemistry, quantum mechanics and electronics. In a bid to shed light on the mechanisms governing these biomimetic nanostructures, this review highlights the significant milestones and breakthroughs that have augmented their current fundamental theory, properties, and utilities. Herein, we elucidate the vast promising crystal chemistry space against the backdrop of known synthesis and characterisation techniques employed in the development and optimisation of this class of honeycomb layered oxides. Further, we highlight key theoretical models that have reinvigorated the exploration and characterisation of within this class of materials and are poised to redefine the frontiers of material research and their applications. We conclude by envisaging future research directions where fascinating physicochemical, topological and electromagnetic properties could be lurking and where valiant efforts ought to be inclined, particularly in the prospective real-isation of exotic material compositional space as well as their utility as testing grounds for emergent two-dimensional (2D) topological quantum gravity and conformal field theories.