Nowadays, solid compounds with crystalline structure formed by inorganic clusters or metal ions (generally transition metals) linked by two or multifunctional organic units, which called metal-organic frameworks (MOFs). In recent years, metal-organic frameworks (MOFs) are valuable materials because of their applications on the preparation of adsorption, catalysis, sensors, electronics, selective separation, fuel cells, petrochemistry, large scale of industrial products and drug delivery [1-2]. N-Heterocyclic compounds such as uracil derivatives are one of the important categories of compounds in the organic synthesis. Quinoline and pyrimidine derivatives containing uracil in their structure are interesting classes of organic compounds because of their pharmacological activity including antitumour, cardiotonic, hepatoprotactive, antihypertensive, antibronchitic and antifungal activity. Pyrimido[4,5-b]quinolone derivatives are a category of fused quinolines separated from the marine bacteria having antibacterial and antifungal activities [3-4]. In the present research, we explored MOFs chemically modified by organophosphonic acid MIL-100(Cr)/NHEtN(CH2PO3H2)2 based on En/MIL- 100(Cr) by a heterogeneous synthetic method, and used it as a task-specific, recyclable and reusable catalyst for the operational and one-pot synthesis of new N-heterocyclic compounds such as tetrahydropyrimido[4,5-b]quinoline-2,4,6(1H,3H,7H)-trione, tetrahydropyrimido[4,5- b]quinoline-4,6(3H,7H)-dione and octahydropyrimido[4,5-b]quinolin-6(1H)-one derivatives
