An arsenicniobate-based 3D porous framework, [Cu(dap)₂]₄[AsNb₁₂O₄₀(VO)₄]·(OH)·7H₂O (1) (dap = 1,2-diaminopropane), was hydrothermally prepared and characterized using the IR spectrum, elemental analysis, powder X-ray diffraction, thermogravimetric analysis and X-ray single-crystal diffraction. Structural analysis shows that the framework is constructed by tetra-vanadyl capped Keggin arsenicniobate [AsNb₁₂O₄₀(VO)₄]⁷⁻ and four [Cu(dap)₂]²⁺ linkers. The framework contains the 1D quadrangular channels of 5.7 × 5.7 Å along the crystallographic c axis. The overall framework is cationic and OH⁻ anions reside in the channels of the framework for charge balance. Considering such a structural feature, we concentrated on the probability of the framework for selective adsorption and anion-exchange. The adsorption properties show that 1 can selectively adsorb water molecules over ethanol to make them separate. Besides, anion-exchange studies for 1 suggest that the OH⁻ anions in the channels can be quantitatively exchanged by SCN⁻ anions.