Composite membranes with a thin selective layer based on poly[1-trimethylsilyl-1-propyne] (PTMSP) and crosslinked PTMSP containing 10 wt % of nanoparticles of porous aromatic frameworks (PAF-11) have been synthesized and studied. Monitoring of changes in the gas transport characteristics of the membranes under ambient conditions for 7500 h has revealed that for all the samples, the transport characteristics abruptly decrease within the first 1000-2000 h; after that, the mass transfer constants gradually change over time. In the case of a composite membrane with the selective layer based on crosslinked PTMSP and PAF-11 nanoparticles, stable permeability values after 7000 h are 2.1, 3.5, and 12.9 m(3)/(m(2) h atm) for N-2, O-2, and CO2,respectively (at an ideal selectivity of alpha(O-2/N-2) = 1.6 and alpha(CO2/N-2) = 6.1); to date, this is the best published result for thin-film composite membranes based on highly permeable glassy polymers.