HEI: Type Material

Framework Type HEI

Reference Material

Material Name:	HPM-18, ordered, calcined
	Ordered member of the Intergrowth Family HPM-18 (see polymorph HPM-18_E)
Chemical Formula:	[Si₄₀Ge₈O₉₆]-HEI [1]
Unit Cell:	Triclinic	P -1 (# 2)
	a' = 20.6596 Å	b' = 10.2995 Å	c' = 14.6012 Å
	α' = 90.205°	β' = 109.358°	γ' = 104.663°
	(Relationship to unit cell of Framework Type as vectors: a' = 0.5a, b' = 0.5a - c, c' = b)
Framework Density:	17.0 T/1000 Å³

Channels:

{[010] 12 4.6 x 8.6* <-> [110] 8 3.3 x 3.3 <-> [110] 8 3.3 x 3.3 }*

Dimensionality
	Sorption (molecular cross section > 3.4Å):	1-dimensional
	Topological (pore opening > 6-ring):	3-dimensional

Note:

The two 8-rings are topologically equivalent, but in this space group they are not equivalent and have slightly different dimensions.
See also the diffusion pathways image on the Framework Type page.

References:
	Yu, H., Zhang, Z., Li, J., Balestra, S.R.G., Rei Gao, Z. and Camblor, M. A.
		"Unexpected Phase Selectivity in Germanosilicate Zeolite Synthesis: Discovery and Structure of HPM-18, a Novel Stable d4r- Containing Structure"
		Journal of Materials Chemistry A, , (2026)

	Name and Code derivation:
		Nanostructured Hybrid, Biohybrid and Porous Materials Group - eighteen HPM-18(eighteen) HEI



	1	Fluoride acts as a second structure-directing agent

Limiting Rings

12-ring viewed along [010]	8-ring No. 1 viewed along [110]

8-ring No. 2 viewed along [110]