In fact, the XB has emerged as a versatile tool with applications in a wide range of domains. In particular, it has been used extensively in fields such as crystal engineering, supra-molecular chemistry, drug design and bio-molecular engineering. These applications have propelled the XB to the forefront of modern chemistry and materials science, promising exciting future prospects. In more recent developments, the XB has ventured into the domain of non-covalent organocatalytic applications, drawing inspiration from the undeniable success of hydrogen-bond (HB)-based organocatalysis. While both the HB and XB share advantageous features such as their electrophilic nature, it is the distinctive properties of XB donor systems that emphasise their potential as a promising alternative to the extensively investigated HB-based catalysis. In comparison to the latter, the XB offers a higher level of tunability. The strength of the XB interaction can be adjusted by modifying the electron-withdrawing characteristics of the covalently bound scaffolding to the halogen atom as well as the polarisability of the XB-donor atom. The size of the σhole, which determines the directionality of the XB-donor system (see Figure ), is directly proportional to the polarisability of the XB-donor atom. This directionality arises from the repulsive forces between the perpendicular lone pairs of electrons, known as the electron belt, and the σ-hole. Recently, Keuper et al 38 leveraged the directional nature of an XB-donor to devise a novel and highly effective enantioselective organocatalytic strategy, demonstrated in the Reissert-type anion-binding reaction. Furthermore, the XB donor exhibits distinctly larger van der Waals radii and hydrophobicity compared with the HB donor counterpart, making it more soluble in non-polar solvents and sensitive to steric hindrance. Consequently, the XB donor is less prone to competition with more polar solvents, which accounts for the applicability of the XB donor in a wide range of organic reactions.