TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Membrane: The templated porous intermediate layer is an inorganic surfactant-templated silica layer, preferably having an average pore size of less than 20 Angstroms. The intermediate layer includes an amphiphilic block copolymer.The microporous layer is an inorganic silica layer, preferably having an average pore size of less than 5 Angstroms.The first inorganic porous membrane has a pore diameter of 10-20 Angstroms, a thickness of less than 100 Angstroms and includes a surfactant-templated material prepared from silica polymers and a surfactant powder.The second inorganic porous membrane is an inorganic silica membrane, preferably having an average pore size of 2-5 (especially 3-4) Angstroms and a thickness of less than 100 nm.The porous substrate is an alumina substrate, preferably having an average pore diameter of 30 to 60 Angstroms.Preferred Method: In method (I), the step (f) includes:(i) calcining the inorganic polymeric coated substrate at a first temperature producing a dual-layered supported membrane; and(ii) further calcining the dual-layered supported membrane at a second temperature to produce the inorganic dual-layered microporous supported membrane.Step (i) is preferably under a vacuum of less than 6 (preferably less than 4) lb/in2 absolute (psia) at 200-400 (preferably 250-350)degreesC. Step (II) is carried out at 300-600 (preferably 400-500)degreesC for 30-90 minutes.The heating of the surfactant-template membrane substrate includes heating at 500-600degreesC for 30-90 minutes. The step (c) includes calcining at 100-150degreesC. The surfactant-template polymeric sol and the second polymeric sol both comprise silica polymers. The sols are prepared and deposited under a low condensation rate. The drying step (e) is performed under low relative pressure of the liquid constituents and the whole method is performed under Class 100 clean room conditions.In method (II), the modifying of the surface of the support includes depositing an intermediate membrane on the surface. This preferably includes:(i) depositing an inorganic surfactant-templated silica intermediate layer having an average pore size of less than 25 Angstroms;(ii) depositing a surfactant-template sol onto the support, drying the surfactant sol coated support and calcining the dried surfactant sol coated support resulting in a surfactant supported membrane; or(iii) removing the surfactant-template by heating the surfactant supported membrane producing the modified support.The step of depositing the top microporous membrane includes:(1) depositing an inorganic polymeric sol on the modified support;(2) drying the polymeric sol coated support resulting in an inorganic polymeric sol coated support;(3) calcining the inorganic polymeric sol coated support resulting in a dual-layered supported membrane;(4) further calcining the dual-layered supported membrane resulting in the supported membrane capable of molecular sieving.