A gas separation membrane comprising the following layers: (i) a support layer; (ii) a layer comprising a crosslinked polysiloxane; (iii) a discriminating layer comprising groups of the Formula (1): M-(O).sub.x, wherein: M is a metal or metalloid atom; O is an oxygen atom; and x has a value of at least 4; (iv) optionally a layer which comprises a fluorinated polymer; and (v) optionally a protective layer; wherein: (a) layer (ii) has an atomic ratio of carbon to silicon of 1.6 to 1.98; (b) the discriminating layer comprises a surface comprising at least 10 atomic % of M of Formula (1) groups, wherein M is as hereinbefore defined; and (b) layer (ii) is located between layers (i) and (iii).

There is provided a filtration system comprising a first vessel, a second vessel and a separation layer. The first vessel is adapted to receive a liquid phase. The second vessel is in fluid communication with the first vessel and is adapted to receive a permeate of the liquid phase. The separation layer separates the first vessel and the second vessel. The separation layer is porous and the pores allow for the filtering of the liquid phase. The separation layer comprises a graphitic material, crosslinkers and a polymer coating.

A gas separation membrane comprising the following layers: (i) a support layer; (ii) a buffer layer; (iii) a discriminating layer; (iv) optionally a fluorinated polymer layer; and (v) optionally a protective layer; wherein: (a) the buffer layer (ii) and the discriminating layer (iii) each independently comprise groups of Formula (1): M-(O).sub.x Formula (1) wherein: each M independently is a metal or metalloid atom; O is an oxygen atom; and each x independently has a value of at least 4; (b) the buffer layer (ii) comprises a surface comprising 4 to 10 atomic % of M of Formula (1) groups, wherein M is as hereinbefore defined; (c) the discriminating layer (iii) comprises a surface comprising more than 10 atomic % of M of Formula (1) groups, wherein M is as hereinbefore defined; and (d) layer (ii) is located between layers (i) and (iii).