Microwave heating is an alternate means for material processing. The technique is promising for the accelerated synthesis of new materials. Microwave molecular sieves synthesis is combined with capillary confinement as a novel synthetic method. It is successfully demonstrated in the preparation of small ZSM-5 crystals by microwave hydrothermal synthesis within 1–1.7 μm channels of a capillary bundle. The geometric and spatial confinement offered by the capillary is expected to define and control the resulting crystal size distribution and orientation.

MCM-41, a mesoporous molecular sieve with a uni-dimensional regular array of hexagonal channels is investigated as a candidate for capillary confinement. The large porous channels of MCM-41(>35 å ) is attractive as a host for promoting inclusions of guest molecules or templates. The successful confinement of MCM-41 represents an important step towards the alignment of molecular sieves in a defined orientation within thin capillaries bundled (less than 5 μm channels). Ultimately, such an approach may be useful for the fabrication of new molecular sieve devices.