A novel and facile biomineralization-inspired approach to fabricating the polymer-inorganic nanocomposite membrane was proposed utilizing manifold functions of polymer: forming the ultrathin membrane scaffold, inducing (templating and catalyzing) the in situ generation of inorganic nanoparticles, confining and suppressing the aggregation of inorganic particles. More specifically, ultrathin gelatin-silica nanocomposite membranes (0.4-0.6 mu m) with homogeneously dispersed silica nanoparticles (40-80 nm) were fabricated onto a porous substrate mildly and rapidly. The morphology and the size of the silica nanoparticles can be conveniently tuned by simply varying the fabrication conditions such as concentration of the silica precursor, pH value of the membrane casting solution. The as-prepared membranes displayed well-defined free volume characteristics, and superior dehumidification performance. The dehumidification experiments using 0.3 wt.% water vapor/propylene mixture gas as model showed that water permeance was 1.87 x 10(-8) m(3)(STP)/(m(2) s Pa) and separation factor was infinite for the composite membranes fabricated at the sodium silicate concentration 30 mM and the pH 7.0. (C) 2010 Elsevier B.V. All rights reserved.