Enhancement of co2/ch4 permselectivity via thermal rearrangement of mixed matrix membranes made from an o-hydroxy polyamide with an optimal load of a porous polymer network

•MMMs, with loads of PPN (TRP-TFAP) in an HPA (6FCl-APAF) matrix, have been thermally rearranged.•Mechanical, thermal and morphological properties of the resulting β-TR membranes have been studied.•CO2/CH4 selectivity of MMMs decreased slightly with increasing PPN loads and after TR.•CO2 permeabilities were optimal for 30% PPN arriving to the 2008 Robeson’s bond.•Changes in compaction, rigidity, fractional free volumes and filling-matrix interactions explain permselectivity.