Multifunctional lanthanum tetraphosphonates: Flexible, ultramicroporous and proton-conducting hybrid frameworksElectronic supplementary information (ESI) available: Fig. S1S3: XRPD Rietveld plots for compounds 13; Fig. S4: Comparison of the raw powder patterns for Ln(H5DTMP)7H2O (Ln = La, Sm); Fig. S5: framework view for 1 showing the 1D channels; Fig. S6: lattice water molecule chain within the channel of 1. Tables S1S3: Bond lengths and H-bonding distances for compounds 13. CCDC reference numb

A new flexible ultramicroporous solid, La(H 5 DTMP)7H 2 O ( 1 ), has been crystallized at room temperature using the tetraphosphonic acid H 8 DTMP, hexamethylenediamine- N,N,N , N - tetrakis (methylenephosphonic acid). Its crystal structure, solved by synchrotron powder X-ray diffraction, is characterised by a 3D pillared open-framework containing 1D channels filled with water. Upon dehydration, a new related crystalline phase, La(H 5 DTMP) ( 2 ) is formed. Partial rehydration of 2 led to La(H 5 DTMP)2H 2 O ( 3 ). These new phases contain highly corrugated layers showing different degrees of conformational flexibility of the long organic chain. The combination of the structural study and the gas adsorption characterization (N 2 and CO 2 ) suggests an ultramicroporous flexible framework. NO isotherms are indicative of a strong irreversible adsorption of NO within the pores. Impedance data indicates that 1 is a proton-conductor with a conductivity of 8 10 3 S cm 1 at 297 K and 98% of relative humidity, and an activation energy of 0.25 eV. A new flexible ultramicroporous solid, La(H 5 DTMP)7H 2 O ( 1 ), has been crystallized at room temperature using the tetraphosphonic acid H 8 DTMP, hexamethylenediamine- N,N,N , N - tetrakis (methylenephosphonic acid).