Hybrid open-frameworks. Hydrothermal synthesis and structure determination of MIL-40 or V IV O(H 2 O){HO 3 P–CH 2 –(C 6 H 4 )–CH 2 –PO 3 H}: a lamellar vanadodiphosphonate prepared with p -xylendiphosphonic acid

Abstract V IV O(H 2 O){HO 3 P–CH 2 –(C 6 H 4 )–CH 2 –PO 3 H} labelled MIL-40 is a hybrid organic–inorganic compound whose bidimensional structure is built up from (V IV =O) 2+ vanadyl groups and p -xylendiphosphonate units. MIL-40 was hydrothermally prepared at 443 K and its structure solved from single crystal X-ray diffraction data. It is triclinic (space group P 1 , n° 2) with lattice parameters a  = 7.255 8(8) A, b  = 7.573 9(8) A, c  = 11.493(1) A, α  = 93.230(2) °, β  = 103.018(2) °, γ  = 96.871(2) °, V  = 608.7(1) A 3 , Z  = 2, R 1 ( F 0 ) = 0.091 1, wR 2 ( F 0 2 ) = 0.189 6 for 2 843 unique reflections with I  ≥ 2  σ ( I ). Its thermal decomposition is investigated.