Thin film composite membranes (TFC) of polyamide (PA) prepared by interfacial polymerization (IP) between a diamine and an acyl chloride are applied to industrial nanofiltration and reverse osmosis. Water, to dissolve the diamine, and n-hexane, to dissolve the acyl chloride, solvents are involved in the IP process. Eliminating the use of n-hexane would be crucial to produce a greener TFC membrane synthesis method. This is achieved here by carrying out an interfacial polymerization from the vapor phase. First, the membrane support was impregnated with the aqueous diamine solution. Second, the support with the diamine was contacted with vapors of the acyl chloride to unchain the IP reaction. Besides the absence of n-hexane, acyl chloride was applied more efficiently avoiding its loss during the cleaning operations carried out in the typical IP process. These membranes were applied in the nanofiltration of simulated micropollutants in water (rose Bengal, sunset yellow and acridine orange dyes), with higher water permeance (up to 3.3 L·m⁻²·h⁻¹·bar⁻¹) than that of conventional TFC membranes and dye rejections higher than 94% in all cases.