The invention provides a membrane suitable for dewatering acidic mixtures, comprising a bridged organosilica directly applied on a macroporous support in the absence of an intermediate mesoporous or finer layer. The bridged organic silica comprises divalent C1-C9 organic groups A2 and/or trivalent C1-C9 organic groups A3 directly bound to the silicon atoms of the organosilica. In particular, the membrane comprises bis-silylmethane or bis-silylethane groups. The membranes effectively separate water from acidic mixtures at high temperatures and without decrease in performance for at least several months.