It has remained a great difficulty and challenge to prepare BN-based porous monoliths (BNPMs) via a facile method. Here, we report a brand-new and high-throughput synthesis of BNPMs through a facile two-step template-free reaction including self-bubbling precursor solidification and high-temperature pyrolysis. The resulting BNPMs with an interconnected open-bubble structure exhibit the highest specific surface area ever reported for the BNPM systems, up to 1406 m2 g-1, and high bulk crush strength of ���1 MPa. Thanks to the spacious hydrophobic surfaces of the BNPM system, the material was applied for the highly efficient separation-adsorption purification of an oil/water system, demonstrating an excellent adsorption capacity of up to 71-98% (volume-based adsorption capacity) toward a wide selection of oil contaminants. Besides, the present BNPMs were designed as a filtration column which rapidly removed rhodamine B (RB) and Cd(II) pollutants from an aqueous solution under a forced filtration-adsorption process, corresponding to an ultrahigh removal capacity of 554 mg g-1 and 561 mg g-1, respectively. Thus, the obtained BNPMs are envisaged to become a fairly promising adsorbent for water cleaning.