Dongzhi Yang

Low-permeability heterogeneous porous media commonly exhibit preferential flow through high-permeability channels and persistent residual-oil trapping in small pores and dead-end regions, limiting effective multiphase transport and residual-oil mobilization. Herein, Ca2+-responsive polyacrylamide/sodium alginate nanogel spheres (PAM/SA NSGs) were developed as an environment-responsive nanogel system for Ca2+-rich porous media. In simulated formation water, SA–Ca2+ coordination increased the apparent elastic modulus from 1.35 MPa for PAM NSGs to 3.45 MPa for PAM/SA NSGs and enabled the composite nanogel spheres to retain their morphology after hydrothermal aging at 60 °C for 14 days. The PAM/SA NSG emulsion dispersion reduced the crude-oil/water interfacial tension from approximately 32 to 12.6 mN·m–1 and produced smaller and more stable emulsified droplets than the PAM control. Microfluidic visualization showed that PAM/SA NSGs generated stronger pressure fluctuations, promoted flow redistribution toward less-swept pores, and increased displacement efficiency from 46.8% after water flooding to 65.3%. Post-displacement observations revealed stripe-like accumulation, surface deposition, and localized bridging without complete pore blockage, interfacial enrichment, and downstream migration of emulsified oil droplets, supporting the coupling of local flow regulation with in situ macroemulsion formation. Core flooding further showed that PAM/SA NSGs maintained stronger flow-resistance regulation after aging and achieved a final oil recovery of 48.7%, representing a 13.5-percentage-point increase over water flooding. These results establish an environment-responsive nanogel strategy in which Ca2+, conventionally regarded as detrimental to chemical flooding, is repurposed as an environmental trigger for nanogel reinforcement to couple mechanical stability, interfacial regulation, and multiphase transport in low-permeability heterogeneous porous media.

Deformable polymer hydrogels are widely used in temporary plugging during hydraulic fracturing and for deep profile control. However, simultaneously optimizing deformation-enabled sealing stability, pressure-bearing plugging strength, and controllable removal after plugging remains challenging. In this study, hydrolytically cleavable cross-linking structures were introduced into a polyacrylamide (PAM) network through a scalable one-step polymerization strategy, enabling degradation under reservoir conditions. Stepwise dehydration was subsequently applied to reconstruct the internal hydrogen-bonding network, thereby regulating the mechanical strength, plugging performance, and degradation behavior of the hydrogel. After 6 h of dehydration, hydrogen-bond network reconstruction and polymer chain rearrangement promoted hydrogel network densification, increasing the compressive stress at 90% strain from 1.42 to 17.9 MPa and the breakthrough pressure from 0.47 to 3.98 MPa while prolonging the duration of stable plugging. After plugging, the hydrogel gradually degraded within 120 h into a polymer solution with a viscosity of 5.07 mPa·s, potentially facilitating plug removal and reducing the risk of long-term formation damage. Additionally, hydrogel nanospheres based on the same formulation were prepared via inverse emulsion polymerization for deep profile control in low-permeability reservoirs. Core flooding experiments showed that the oil displacement efficiency reached 60.4% after swelling for 7 days, representing an increase of 24.7 percentage points over water flooding. This study provides a design strategy for controllably degradable PAM-based hydrogel systems for petroleum recovery.

Efficient catalytic detoxification of nerve agents under atmospheric conditions is severely hindered by the lack of water and poor accessibility of catalytic sites. Herein, a polyamide 56 (PA56)-based nanonet membrane with spontaneous hygroscopicity and self-buffering capacity is designed for efficient catalytic detoxification of dimethyl-4-nitrophenyl phosphate (DMNP), a representative nerve agent simulant, which is fabricated by the in situ growth of metal-organic frameworks (UiO-66-NH₂) on a spider-web-like electrospun PA56 nanofibrous membrane, followed by the integration of hygroscopic LiCl and alkaline polyethylenimine (PEI). The unique 2D nanonet structure within the interfiber pores significantly increases the nucleation sites of UiO-66-NH₂ on the membrane, leading to a high MOF loading of 42.1 wt %, and thus a significantly shortened hydrolysis half-life of 2.8 min against DMNP in an aqueous solution. The synergistic hygroscopic effect of PEI and LiCl enables the membrane to achieve an atmospheric moisture uptake of up to 1.70 g g^-1, which in turn facilitates the diffusion of DMNP. As a result, in an atmospheric environment, DMNP can be eventually converted into the nontoxic products of dimethyl phosphate (72%) and methyl phosphate (28%), with a hydrolysis half-life of 1.9 h. Additionally, the lightweight catalytic membrane exhibits effective barrier protection against DMNP aerosol/droplets. This work provides a methodology for fabricating self-detoxifying wearable devices against chemical warfare agents under atmospheric conditions.

Although solar-driven water evaporation is promising for mitigating water scarcity in the areas lacking clean water and far away from power grids and water grids, the low solar energy utilization, high water vaporization enthalpy, and salt deposition seriously impede its practical application for continuous, efficient, and stable desalination of seawater. Herein, siphoning and Hofmeister effects-enhanced hanging inverted cone-shaped solar-thermal evaporator with a top-down water supply is designed for efficient solar-thermal desalination of seawater, which is prepared by in situ polymerization of pyrrole on nonwoven cellulose fabrics and subsequent coating with poly(vinyl alcohol) (PVA) hydrogel. The 3D hanging inverted cone structure significantly enlarges the areas for solar-thermal energy conversion and water evaporation, while the top-down water supply via the pressure of the siphoning effect ensures sufficient water, achieving a high water evaporation rate of 3.90 kg m^–2 h^–1 with the water vaporization enthalpy of 2.06 kJ g^–1 during solar-thermal evaporation of pure water under 1-sun irradiation. In an aqueous solution with 3.5 wt % NaCl, the PVA hydrogel generates additional intermediate water via the Hofmeister effect to further reduce the water vaporization enthalpy to 1.61 kJ g^–1, thereby increasing the water evaporation rate to 4.89 kg m^–2 h^–1. Thanks to the significantly enlarged evaporation surface area, the reduced water vaporization enthalpy, and the sufficient top-down water supply, the hanging inverted cone-shaped evaporator with the top-down water supply is highly efficient in continuous desalination of natural seawater, achieving a water evaporation rate of 4.64 kg m^–2 h^–1 with a salt rejection of 99.99%.