A SiH functionalized phenyl-bridged periodic mesoporous organosilica [H-PMO(Ph)] is synthesized via a surfactant-directed assembly approach. Pd nanoparticles are then immobilized onto the PMO catalyst [Pd/H-PMO(Ph)] by a SiH in situ reduction method. The Ullmann reaction, in water as medium, is used to investigate the catalytic performance of Pd/H-PMO(Ph). The results show that the Pd/H-PMO(Ph) catalyst has excellent catalytic activity and selectivity, which can be attributed to synergetic effects derived from the highly dispersed catalytic species and the hydrophobic microenvironments. Furthermore, the catalyst could be conveniently recovered and recycled five times without significant loss of activity and selectivity.