Metal-organic frameworks (MOFs) have shown promise for AWH due to their high uptake capacities and low enthalpies of adsorption. Owing to their desirable properties and good performance, some MOFs have recently been applied practically in large-scale devices. However, the vast majority of MOFs are unstable upon exposure to water, leading to network degradation. Furthermore, more water-stable MOFs could still pose health risks due to the potential leakage of metals into the harvested water. Hence, research on new sorbents for AWH has recently focused on porous organic materials, such as covalent organic frameworks (COFs). Covalent organic frameworks are a class of reticular materials that are synthesised from molecular organic building blocks linked together using reversible condensation reactions. COFs exhibit a range of advantageous features, including high crystallinity, permanent porosity, and a large specific surface area. The wealth of viable structural building blocks and linkages offer some degree of control over the chemical and textural properties, enabling bottom-up application-targeted design. However, successful water sorption in COFs often requires high RH for uptake and large energy input for regeneration due to hysteresis upon water desorption. In an attempt to improve their water uptake, various functional groups were incorporated into the chemical structure of the building blocks of ketoenamine-linked COFs. The incorporation of hydrophilic nitro or hydroxy groups into the backbone led to a shift in the onset of water adsorption to lower RH and improved overall performance. Elsewhere, improvements in hydrophilicity in isostructural azine-linked COFs were achieved by introducing hydroxy groups, again shifting uptake onset to lower RH. Similarly, the replacement of phenyl groups with pyridine units in a COF backbone shifted the onset of significant water uptake from 65% to 25% RH, while retaining the absolute capacity. Aside from modifications of COF surface chemistry, pore size has also been identified as a crucial factor for the water uptake performance. To support water condensation, pore diameters should ideally be between 0.8 and 2 nm, as demonstrated for an imine-linked COF with a voided square grid and a hydrophobic trigonal COF. In contrast to the bottom-up design of COFs via careful choice of their organic building blocks, post-synthetic strategies have emerged as a supplementary route to improved water uptake at lower RH. For example, the post-synthetic oxidation of hydrazine to the hydrazide-linked COFs resulted in a shift in the onset of water adsorption to lower RH without impacting the total uptake capacity. More recently, a post-synthetic strategy was employed to produce nitrone-linked COFs with improved water uptake at low RH from imineand amine-linkages, however, with the detrimental effect of reducing the overall capacity from 0.34 to 0.27 g•g -1 . Despite the ongoing research into improved adsorbents for AWH, the number of COFs with suitable water uptake at 30% RH remains limited and many of these networks cannot capture water below 20% RH, representing some of the harshest environments on Earth.