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Stimuli-responsive molecular systems support within permanently porous materials offer the opportunity to host dynamic functions in multifunctional smart materials. However, the construction of highly porous frameworks featuring external-stimuli responsiveness, for example by light excitation, is still in its infancy. Here a general strategy is presented to construct spiropyran-functionalized highly porous switchable aromatic frameworks by modular and high-precision anchoring of molecular hooks and an innovative in situ solid-state grafting approach. Three spiropyran-grafted frameworks bearing distinct functional groups exhibiting various stimuli-responsiveness are generated by two-step post-solid-state synthesis of a parent indole-based material. The quantitative transformation and preservation of high porosity are demonstrated by spectroscopic and gas adsorption techniques. For the first time, a highly efficient strategy is provided to construct multi-stimuli-responsive, yet structurally robust, spiropyran materials with high pore capacity which is proved essential for the reversible and quantitative isomerization in the bulk as demonstrated by solid-state NMR spectroscopy. The overall strategy allows to construct dynamic materials that undergoes reversible transformation of spiropyran to zwitterionic merocyanine, by chemical and physical stimulation, showing potential for pH active control, responsive gas uptake and release, contaminant removal, and water harvesting.A post-synthetic strategy for the construction of highly porous aromatic frameworks is presented. This approach enables the fabrication of a series of materials with a wide range of properties and applicability in diverse fields.image

The new scientific decade (2023-2032) of the International Association of Hydrological Sciences (IAHS) aims at searching for sustainable solutions to undesired water conditions – whether it be too little, too much or too polluted. Many of the current issues originate from global change, while solutions to problems must embrace local understanding and context. The decade will explore the current water crises by searching for actionable knowledge within three themes: global and local interactions, sustainable solutions and innovative cross-cutting methods. We capitalise on previous IAHS Scientific Decades shaping a trilogy; from Hydrological Predictions (PUB) to Change and Interdisciplinarity (Panta Rhei) to Solutions (HELPING). The vision is to solve fundamental water-related environmental and societal problems by engaging with other disciplines and local stakeholders. The decade endorses mutual learning and co-creation to progress towards UN sustainable development goals. Hence, HELPING is a vehicle for putting science in action, driven by scientists working on local hydrology in coordination with local, regional, and global processes.

Water fluxes at ecohydrological interfaces are a key driver for biogeochemical processing and they influence habitat properties. This chapter covers methods which are specifically suitable for the stream–groundwater interface. The point-scale approaches, however, can be applied in the general context of groundwater–surface water interactions, e.g. for lakes. Water fluxes across the stream–streambed interface are practically never homogeneous in space. Point methods are used to detect water fluxes across the stream–groundwater interface at one point or spot. Point methods comprise direct observation of water fluxes with seepage meters, methods based on Darcy's law, as well as natural and artificial tracer techniques. Reach-scale integral methods can be used when the spatial scale of interest is so large that multiple point measurements become infeasible.

In this chapter, the authors aim to uncover the organizational principles – the main drivers and controls, and their interactions and feedbacks – that determine the development and capacity of ecohydrological interfaces to transform the flow of energy, water, and matter between adjacent ecosystems. They compare the characteristics of transformation processes at different ecohydrological interfaces in freshwater ecosystems, including groundwater–surface water, groundwater–vadose zone, and benthic–pelagic interfaces, to determine common or unique features of their non-linear process dynamics. Based on a comparison of the organizational principles of different ecohydrological interfaces, the authors propose a roadmap for the development of multi-scale conceptual models of ecohydrological interface processes and their interactions that can be expanded to other types of ecohydrological interfaces.

Submarine groundwater discharge (SGD) at the interface of land and sea is likely an important part of the global hydrological cycle and has started to attract the attention of a growing interdisciplinary scientific community. Independent of its composition, SGD is of particular relevance for estuarine and coastal areas, since it provides a direct pathway for element and water flow at the connection between land and ocean. Freshwater discharge rates and age may be highly variable, depending on the local hydrogeology. Since SGD may be enriched in nutrients, dissolved inorganic carbon, methane, and metals, it is linked to society-relevant issues, such as coastal eutrophication and the development of harmful algal blooms, the development of hypoxia, greenhouse effect, as well as ocean acidification to mention a few. Due to the direct measurement of the SGD composition and fluxes on small scales, however, biogeochemical and physical contributions to the adjacent coastal water column can be deduced.

In this chapter, the authors provide a comprehensive analysis and synthesis of the interactions between important drivers and controls of hyporheic exchange and biogeochemical cycling and how they vary across scales, integrating results from a wide range of case studies that go beyond current conceptual model frameworks. They discuss the interactions of different local-to-regional controls and drivers of hyporheic zone processes such as hydrodynamic and hydrostatic drivers of hyporheic exchange, sediment hydraulic conductivity, the role of autochthonous organic matter sources, and feedbacks between hydrological exchange and ecological processes in the streambed. The authors explore the implications of these interactions for biogeochemical cycling in the landscape context. They integrate conceptualizations of organizational principles of hyporheic exchange and biogeochemical cycling from reach to catchment scale. The authors expect that increasing awareness and embracing the landscape organizing principles of hyporheic zones will advance the future of research at groundwater–surface water interfaces.

Ecohydrological interfaces comprise liquid–solid interfaces such as the stream–sediment interface, gas–solid interfaces such as the soil–atmosphere interface, liquid–liquid interfaces such as a thermocline in a lake, or gas–liquid interfaces such as the lake–atmosphere interface. The interface at which heat as a tracer is mostly applied is the sediment–water interface at streams, lakes, and seas. It is important to note the underlying difference between heat transport and solute transport in porous media. Temperature differences can be used to identify patterns of groundwater exfiltration over large areas. Thermal infrared imaging reveals the temperature distribution of surfaces and allows the determination of the skin temperature of water bodies but not temperatures in a water body itself. Similar to streambed temperature mapping, the thermal patterns observed along the cable can provide a qualitative indicator of groundwater discharge.

The new scientific decade (2023-2032) of the International Association of Hydrological Sciences (IAHS) aims at searching for sustainable solutions to undesired water conditions - may it be too little, too much or too polluted. Many of the current issues originate from global change, while solutions to problems must embrace local understanding and context. The decade will explore the current water crises by searching for actionable knowledge within three themes: global and local interactions, sustainable solutions and innovative cross-cutting methods. We capitalise on previous IAHS Scientific Decades shaping a trilogy; from Hydrological Predictions (PUB) to Change and Interdisciplinarity (Panta Rhei) to Solutions (HELPING). The vision is to solve fundamental water-related environmental and societal problems by engaging with other disciplines and local stakeholders. The decade endorses mutual learning and co-creation to progress towards UN sustainable development goals. Hence, HELPING is a vehicle for putting science in action, driven by scientists working on local hydrology in coordination with local, regional, and global processes.

The integration of photoswitchable elements into porous solids provides fascinating opportunities to modulate material properties. However, the fabrication strategies of these materials are dedicated only to preserving the function of the photoswitches in the solid while introducing new properties beyond those offered by the individual components remains challenging. Here, we present a three-state porous aromatic framework constructed from a bistable overcrowded alkene-based photoswitch. The framework was fabricated using a Yamamoto coupling polymerization of an engineered hexadentate monomer to yield swellable and hierarchical microporous/mesoporous architectures with densely integrated photoswitches. The interplay of hierarchical porosity, flexible backbone, and reversible photoisomerization between two isomers generates three unique and distinct porosity states that can be accessed in sequence upon application of external stimuli to induce sponge-like behavior. This material represents a major step toward light-responsive materials capable of harnessing limited molecular-scale motion and converting it into an on-demand response over hierarchical length scales toward a practical output.