Solar hydrogen production via the photoelectrochemical water-splitting reaction is attractive as one of the environmental-friendly approaches for producing H 2. Since the reaction simultaneously generates H 2 and O 2 , this method requires immediate H 2 recovery from the syngas including O 2 under high-humidity conditions around 50 • C. In this study, a supported mesoporous γ-Al 2 O 3 membrane was modified with allyl-hydrido-polycarbosilane as a preceramic polymer and subsequently heat-treated in Ar to deliver a ternary SiCH organic-inorganic hybrid/γ-Al 2 O 3 composite membrane. Relations between the polymer/hybrid conversion temperature, hydrophobicity, and H 2 affinity of the polymer-derived SiCH hybrids were studied to functionalize the composite membranes as H 2-selective under saturated water vapor partial pressure at 50 • C. As a result, the composite membranes synthesized at temperatures as low as 300-500 • C showed a H 2 permeance of 1.0-4.3 × 10 −7 mol m −2 s −1 Pa −1 with a H 2 /N 2 selectivity of 6.0-11.3 under a mixed H 2-N 2 (2:1) feed gas flow. Further modification by the 120 • C-melt impregnation of low molecular weight polycarbosilane successfully improved the H 2-permselectivity of the 500 • C-synthesized composite membrane by maintaining the H 2 permeance combined with improved H 2 /N 2 selectivity as 3.5 × 10 −7 mol m −2 s −1 Pa −1 with 36. These results revealed a great potential of the polymer-derived SiCH hybrids as novel hydrophobic membranes for purification of solar hydrogen.