Azamacrocycles and the azaoxacryptand 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane as structure-directing agents in the synthesis of microporous metalloaluminophosphates

Abstract

Hydrothermal syntheses of aluminophosphates have been performed in the presence of Mg2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ cations using the macrocycles 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn), 1,4,8,11-tetraazacyclotetradecane (cyclam), 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (tmtact) and 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane (hmhaco), and the cryptand 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (K222) as structure directing agents. Tmtacn is found to template MAPO-18, K222 to template MAPO-42 and tmtact to template STA-6 or STA-7; the solids formed using tmtact depend on the metal cation present. Use of cyclam with a cobalt aluminophosphate gel results in a new solid, CoII(C10N4H24)Al(PO4)PO3(OH), which consists of aluminophosphate chains of stoichiometry AlP2O8H linked via cobalt–cyclam complexes. Bonding between the cobalt–cyclam complexes and the aluminophosphate chains is through direct Co–O bonds and a complex hydrogen-bonding network—quite different from that between the three-dimensionally connected frameworks and the tertiary amine-containing templates. An isostructural solid is formed via the substitution of cobalt by nickel in the aluminophosphate gel. The role of divalent cations in structure direction, in the presence of tertiary amine-containing macrocycles, has been further investigated. Adding Co2+ or Zn2+, in particular, enhances the amines’ ability to act as templates for STA-7 and MAPO-42, yet single crystal and powder diffraction using synchrotron radiation indicates that the divalent cations do not remain within the macrocycles after crystallisation.