Porous mullite and mullite-alumina composites have been developed from China clay and aluminium fluoride trihydrate (AlF3·3H2O) with various amounts of Al2O3. China clay undergoes a moisture aided vapour phase reaction with AlF3·3H2O during sintering, forming a porous mullite network having needle-shaped interlocking microstructure from 1300 °C onwards. Al2O3 powder has been added to this powder mixture in varying quantities and sintered at different temperatures. The properties of the samples, such as pore characteristics, pure water flux and strength have been evaluated. It is found that the developed membrane sample added with 10 wt% alumina and sintered at 1400 °C showed excellent water flux, high open porosity and flexural strength owing to its highly interlocked mullite crystals forming the microstructure. The addition of alumina enhanced the mechanical properties of the sample significantly. The optimum combination of precursor powders and sintering condition needed for the fabrication have been found out. The developed porous mullite can be used for microfiltration applications directly or as a support for developing additional membrane layers for separation. © 2019 Elsevier B.V.