Effect of nanopore network connectivity on the phase behavior of confined associating fluids

We investigate the phase behavior of associating fluids inside heterogeneous slit pores. Two distinct phase transitions are observed for connected pores of two slit widths for both hard and attractive walls. In the case of the hard wall, the wider pore undergoes the vapor-liquid transition earlier than the narrower pore due to its weaker confinement and increased fluid interactions. In the case of an attractive pore surface, the narrower pore undergoes the vapor-liquid transition earlier than the wider pore. This can be attributed to the enhanced surface interactions in the narrower pore, which promote the condensation of the fluid phase. The x-density profile of the systems reveals that the interfacial fluid molecules play an essential role in early/delayed phase transition in the respective pores of the heterogeneous systems.