Mercury contamination is one of the major environmental and health issues that has been affecting our lives for several decades. To address this matter, a rational design of robust adsorbent materials bearing chelating sites for binding with Hg²⁺ is highly desirable. Porous organic materials have recently emerged as excellent adsorbent materials for heavy metal ions and toxic gases. These porous nanomaterials are generally synthesized via bottom-up chemical reactions, which offer ample opportunities for modifying their structure through the incorporation of various functional sites, thereby, rendering them as an essential platform for designing flexible materials with numerous applications. Scalable synthetic approaches, together with high specific surface area and robustness of framework distinguishes porous organic materials, such as porous organic polymers (POPs) and covalent organic frameworks (COFs), as versatile and indispensable nanoscale materials along with other frontline porous materials including porous carbons, zeolites, aluminophosphates, metal–organic frameworks (MOFs), functionalized mesoporous silica, and periodic mesoporous organosilicas (PMOs). It is worthy to mention that a tailorable structural design approach of POPs and COFs offer adjustable surface property in terms of specific surface area, pore size, and functionality, which can be advantageous towards achieving a benchmark adsorbent material for the detoxification of wastewater to counter harmful environmental effects. Although POPs/COFs are outstanding in removing mercury from contaminated water, to the best of our knowledge, till date, there is hardly any comprehensive review that exclusively highlights all such discoveries. In this review, we highlight some major achievements in the synthesis of porous organic materials and their potential as adsorbents for the removal of Hg(II) from different water resources including actual conditions together with their future potential in water purification technologies.