The Fe3+ ion is the most important element in environmental systems and plays a fundamental role in biological processes. Iron deficiency can result in diseases and highly selective and sensitive detection of trace Fe3+ has become a hot topic. A novel two‐dimensional ZnII coordination framework, poly[[μ‐4,4′‐bis(2‐methylimidazol‐1‐yl)diphenyl ether‐κ2N3:N3′](μ‐4,4′‐sulfonyldibenzoato‐κ2O:O′)zinc(II)], [Zn(C14H8O6S)(C20H18N4O)]n or [Zn(SDBA)(BMIOPE)]n, (I), where H2SDBA is 4,4′‐sulfonyldibenzoic acid and BMIOPE is 4,4′‐bis(2‐methylimidazol‐1‐yl)diphenyl ether, has been prepared and characterized by IR, elemental analysis, thermal analysis and X‐ray diffraction analysis, the latter showing that the coordination polymer exhibits a threefold interpenetrating two‐dimensional 44‐sql network. In addition, it displays a highly selective and sensitive sensing for Fe3+ ions in aqueous solution.