Tunable Morphosynthesis of Calcium Carbonate in Aqueous Solution Enabled by Janus Membrane

Abstract Targeted and high throughput manufacture of crystalline biominerals with diverse morphologies is of importance, due to the significant impact of shape and texture on the material properties, while tunable morphosynthesis of crystalline is restrained by the proper ion transfer process during the reactive crystallization, and is commonly regulated using organic soluble additives. Herein, Janus membranes (JMs) are facilely produced for the continuous confined reactive crystallization of calcium carbonate. Fabricated JM simultaneously achieves rapid and uniform directional CO 3 2− ions transfer in the aqueous solution through the straight, uniform nanoscale hydrophilic channels, and the interfacial reactive crystallization is generated with confined ion adsorption and gating effect at the hydrophobic side. Hollow CaCO 3 microcomposites via JM system are continuously and directly synthesized in the aqueous system without any assisted organic solvent or polymer additive, which is green and highly efficient. In addition, the reversed ion transfer direction in JM can be ideally managed resulting in highly selective manufacturing of cube or sphere‐type microcomposites. This study provides a feasible route for the rapid production of advanced particle materials with tunable morphology, displaying great potential applications of JM in material engineering.