Water confinement is ubiquitous and it plays vital roles in geological, biological and artificial systems with many applications 1, 2, 3, 4, 5, 6, 7, 8. To develop water confinement systems, extensive studies have been conducted over the past 60 years on a variety of hydrogel polymers with various hydrophilic backbones and different functionalities 1, 2, 3. However, the lack of mechanistic strength and immobile water state have precluded their real implementation in water uptake and transport. To create porous structures, researchers have relied on bottom-up strategy via self-assembly of block polymers 9, 10, 11. However, it is difficult to prepare stable and well-defined channels from phase-separated polymers. In recent years, a variety of porous polymers bearing intrinsic porosity has been studied extensively for water confinement and uptake 4, 5, 6. Nevertheless, the design of hydrophobic small-pore materials is precluded by a preconception that hydrophobic small pores would eventually repulse water molecules and cannot enable water confinement and uptake. We anticipate hydrophobic supermicroporous covalent organic frameworks (COFs) with compact pore void is indispensable for water cluster occupation. COFs as a crystalline porous framework material, can be constructed via bottom-up polymerization through topological design. Upon judicious selection of building blocks, aromatic components can connect via covalent bonds to grant extended crystalline structure and hydrolytic stability in COFs. Particularly, simplistic design can generate permanent supermicroporous voids that are implausible to collapse. These distinct features can be combined in COFs and are highly desired for supermicropores but hardly accessible to other porous analogues. In this work, we constitute hydrophobic microenvironment entwined with “pseudo-hydrophilicity” strips to promote water confinement at low pressure. We further dive in to investigate the impact of pore size and shape to pinpoint the size threshold and shape for favourable water molecules confinement. We unexpectedly found that pore size threshold is distinctive to each pore shape in creating similar pore environment.