We report a Ag3PO4 microparticle system showing collective behaviors in aqueous medium. Transition between two emergent patterns, namely "exclusion" and "schooling", can be triggered by shift in chemical equilibrium upon the addition or removal of NH3 or in response to UV light. The transitions are consistent with a self-diffusiophoresis mechanism resulting from ion gradients. The reported system is among the few examples of nanomotors that are based on a reversible nonredox reaction and demonstrates new design principles for micro/nanomotors. Potential applications of the reported system in logic gates, microscale pumping, and hierarchical assembly have been demonstrated.