Sustainable fabrication of superhydrophobic and superoleophilic pristine graphene-PDMS sponges via mechanochemical and microwave-assisted processing for efficient passive oil–water separation

The scalable integration of structurally preserved pristine graphene into three-dimensional polymer architectures remains challenging due to dispersion and processing limitations associated with non-oxidized graphitic nano- materials. Here we report a sustainable fabrication strategy for porous pristine graphene–PDMS (PG–PDMS) nanocomposite sponges obtained by coupling solvent-free mechanochemical integration with microwave- assisted polymerization. This approach bypasses conventional graphene oxide–based chemistries and enables the homogeneous incorporation of pristine graphene within a three-dimensional elastomeric scaffold while preserving its sp² lattice and intrinsic physicochemical properties. Structural and spectroscopic analyses confirm the preservation of graphene integrity and its uniform distribution within the polymer network. The composite exhibits improved thermal stability compared to pristine PDMS, with the main thermal degradation temperature increasing from ~474 ◦C for PDMS to ~556 ◦C for PG–PDMS, and good mechanical resilience, sustaining compressive stresses of approximately 0.4 MPa at 60% strain with more than 99% strength retention after 100 compression cycles. The hierarchical porous architecture displays superhydrophobic behaviour with a water contact angle of 154.4 ± 3.9◦ and strong superoleophilicity, enabling rapid oil uptake with absorption capacities ranging from 4.6 to 27.5 g g⁻¹ depending on the oil type. Notably, the material maintains stable absorption performance over at least 100 repeated absorption–squeezing cycles without significant loss of efficiency. A multi-model in vitro evaluation using HaCaT keratinocytes, OECM-1 epithelial cells, and SH-SY5Y neuroblas- toma cells, including MTT viability, ROS generation, and confocal microscopy analyses under direct and indirect exposure conditions, indicates no significant cytotoxic response. The proposed strategy provides a scalable route toward graphene–elastomer composites for oil–water separation and environmental remediation.