Described herein are facile, one-step initiated plasma enhanced chemical vapor deposition (iPECVD) methods of synthesizing hyper-thin (e.g., sub-100 nm) and flexible metal organic covalent network (MOCN) layers. As an example, the MOCN may be made from zinc tetraphenylporphyrin (ZnTPP) building units. When deposited on a membrane support, the MOCN layers demonstrate gas separation exceeding the upper bounds for multiple gas pairs while reducing the flux as compared to the support alone.

Asymmetric articles are described including a porous substrate with two opposing major surfaces and a porous structure extending between the surfaces, and a polymeric coating on one of the major surfaces and extending into the porous structure to a depth of the porous structure. Methods for making an asymmetric composite article are also provided, including providing a porous substrate, treating the porous substrate with a plasma treatment or a corona treatment from one major surface to a depth of the porous structure between the two major surfaces. The method further includes applying a coating solution to the treated porous substrate and drying the coating solution to form a composite asymmetric composite article having a polymeric coating on one major surface and extending into the porous structure to the depth of the treated porous structure.

A composite membrane comprising: a. a porous support; b. a polymeric layer comprising dialkylsiloxane groups and a metal, the polymeric layer being present on the porous support; c. a discriminating layer present on the polymeric layer; and d. optionally a protective layer present on the discriminating layer wherein the polymeric layer has a molar ratio of metal:silicon of at least 0.0005.

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).