In the catalytic oxidation of atmospheric pollutants, VOC molecules typically need to be first adsorbed at active sites of the catalyst, subsequently undergoing the steps of C–H bond activation, oxygen insertion, and deep oxidation of intermediates. In a humid atmosphere, water molecules often prioritize interaction with surface metal sites, acid-base sites, and oxygen vacancies by virtue of their smaller kinetic diameter, extremely rapid diffusion rate, and strong polar characteristics. This severely inhibits the effective adsorption of VOC molecules at physical and weak chemical levels. Furthermore, oxygen vacancies can play multiple roles: (i) facilitating adsorption and activation of O₂ and some pollutant molecules; (ii) influencing water adsorption and dissociation behavior; (iii) accelerating lattice oxygen migration and promote the Mars-van Krevelen (MvK) mechanism; and (iv) either improving catalytic turnover frequencies by enhancing oxygen mobility or becoming the sites for excessive hydroxyl accumulation, depending on their concentration and local environment under humid conditions. Therefore, oxygen vacancies have a dual role, and their beneficial effect depends on balanced defect density, neighboring coordination structure, and hydroxyl removal kinetics.

The advantage of water molecules in adsorption competition is fundamentally determined by the hydrophilicity of the surface microenvironment and the site charge distribution. For example, water molecules very easily occupy oxygen vacancies on the catalyst surface, giving rise to a sharp reduction in the number of active sites available for activating gaseous oxygen molecules. This, in turn, causes a substantial decrease in the abundance of active oxygen (e.g., O₂^-, O₂^2-, O^-, etc.) species within the reaction system, ultimately hindering the deep oxidation of organic intermediates to CO₂^[17]. Furthermore, different types of active centers exhibit variations in their water adsorption modes. For catalytic systems following the Langmuir-Hinshelwood (L-H) mechanism, where both VOCs and oxygen require pre-adsorption, the aggressive intervention of water will simultaneously block the two critical initial steps of VOC substrate enrichment and oxygen activation^[18].

It is noteworthy that the deactivation solely caused by the competitive adsorption of molecular water usually exhibits strong reversibility^[19]. Numerous studies have demonstrated that introducing water vapor in the low-temperature range leads to a significant decrease in VOC conversion, but upon cutting off the moisture provision, catalytic activity often rapidly restores to its initial level. At higher temperatures, however, because the desorption thermodynamics of water are more favorable and the relative adsorption strength of target reactants (e.g., oxygen and aromatic hydrocarbons) at the active sites is enhanced, the inhibitory effect of water weakens significantly^[20]. This temperature dependence and the activity recovery after cutting off water vapor provision fully demonstrate that the catalyst deactivation at this stage primarily stems from dynamic surface physical occupancy rather than substantial damage to the catalyst structure. Therefore, targeting this type of reversible inhibition, weakening water adsorption by constructing hydrophobic interfaces or regulating surface polarity is an effective strategy^[21].

On numerous oxide supports or metal-oxide interfaces, the interference of water molecules is not limited to instantaneous adsorption in the molecular state. They tend to undergo dissociation at defect sites or metal centers, forming surface -OH* with strong chemical bonding. Compared to molecular water, these hydroxyl species possess extremely high desorption energy barriers and are prone to irreversible accumulation on the catalyst surface, thereby triggering persistent site passivation. This signifies that the deeper hazard of moisture lies in the transformation of water molecules into the chemical “poisons” that are difficult to eliminate [Figure 1]^[22].

The inhibitory mechanism of the substantial accumulation of surface hydroxyls on the catalytic oxidation of VOCs is primarily manifested in three dimensions: (i) The direct blocking of active sites. Strongly bound hydroxyls can persistently occupy precious metal active centers and oxygen vacancies at the metal-support interface, completely cutting off the contact channels for VOCs and O₂; (ii) The blockage of the active oxygen cycle [failure of the MvK mechanism]. In the classical MvK mechanism, gas-phase oxygen molecules are activated at oxygen vacancies to replenish the consumed lattice oxygen species. Hydroxyl coverage not only significantly raises the activation energy for oxygen molecule adsorption and cleavage but also hinders the generation of highly active oxygen (e.g., superoxide and peroxide) species, causing the entire catalytic cycle to stagnate due to “oxygen deficiencies”; (iii) The reshaping of the local microenvironment and reaction pathways. The substantial accumulation of hydroxyls alters the local electronic structure (e.g., d-band center shift), surface acidity or basicity, and even the hydrogen-bonding network of the catalytic interface. This alteration not only increases the desorption difficulty of intermediates but is also highly prone to inducing side reaction pathways, giving rise to the deposition of multi-carbon intermediates (e.g., formates and acetates) on the surface that would increase the risk of coking poisoning^[23,24].

Owing to the extreme difficulty of hydroxyl desorption at low temperatures and the slow rates of bulk lattice oxygen migration and surface regeneration, the poisoning effect triggered by hydroxyl accumulation manifests a particularly severe degree under low-temperature and high-humidity operating conditions^[25]. Therefore, the activity retention rate of a catalyst under the conditions of low-temperature and high-humidity often reflects its intrinsic resistance to hydration poisoning more accurately.

After long-term irreversible damage beyond the reversible or semi-reversible inhibition caused by surface adsorption and hydroxylation, the catalysts undergo profound microstructure evolution in long-term humid and hot service environments, triggering complete irreversible catalyst deactivation. This process is generally referred to as “hydrothermal reconstruction”, which involves surface dissolution-redeposition, crystal phase transformation, sintering of the active phases, and disintegration of the metal-support interfaces.

For supported precious metal (e.g., Pt, Pd, or Ru) or transition metal catalysts, high-temperature water vapor can significantly weaken the SMSI. The intervention of water molecules lowers the migration barrier of metal surface atoms, accelerating the Ostwald ripening and particle agglomeration processes. This directly gives rise to a sharp reduction in metal dispersion and the disappearance of low-coordination, high-activity sites, with catalytic intrinsic activity and water resistance subsequently suffering a cliff-like decline^[26].

For oxide supports, long-term exposure to moisture not only triggers deep bulk hydroxylation but also permanently passivates intrinsic surface defect sites (e.g., oxygen vacancies), causing them to lose crucial oxygen storage/release and oxygen-exchange capacities. Furthermore, in some porous materials (e.g., zeolites, MOF derivatives, or mesoporous metal oxides) with high surface areas, the hydrothermal stress can cause micropore blockage, pore wall shrinkage, or even overall collapse of the framework architecture, fundamentally cutting off the mass transfer channels^[27]. The weakly adsorbed surface hydroxyls are generally more reversible and can be desorbed upon changing atmosphere or temperature; however, the strongly bound lattice hydroxyls are more persistent and more closely associated with irreversible blockage of oxygen migration and the MvK pathway. Moreover, these methods provide multi-dimensional analytical means for clarifying dynamic behaviors of the catalytic surface active sites: (i) operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to monitor hydroxyl vibration bands and their dynamic evolution; (ii) near-ambient-pressure X-ray photoelectron spectroscopy (XPS) to track chemical-state changes of surface oxygen and hydroxyl species; and (iii) in situ Raman and infrared spectroscopy (IR) isotope-labeling experiments to distinguish the adsorbed water-derived species from the lattice-involved hydroxyls.

In summary, water-induced catalyst deactivation is not a single event but a continuous dynamic evolution process “from surface to bulk and from reversible to irreversible”: In the initial stage, water molecules lead to rapid depletion of the active sites through competitive adsorption of reactants and water; subsequently, the surface hydroxyls generated by dissociation of water deeply lock oxygen cycles and interfacial charge transfer; and after long-term hydrothermal accumulation, this surface inhibition eventually evolves into fatal structural deactivation, such as particle sintering, support hydroxylation, and framework collapse. Therefore, enhancing the water resistance of catalysts must not rely on the blind optimization of a single parameter, but rather on comprehensive defensive design around the entire chain mechanism of “competitive adsorption-hydroxyl poisoning-structural reconstruction”. Based on this, the next section presents the key material design strategies developed in recent years for improving the water resistance of catalytic VOC oxidation.

Single-atom catalysts (SACs), by virtue of their ultimate atom utilization efficiency, well-defined local coordination environments, and unique electronic structures, exhibit revolutionary potential in the field of water-resistant catalysis^[28,29]. Compared to conventional nanoparticle (NP) catalysts, the most prominent water-resistance mechanism of single-atom sites is first manifested in the “spatial isolation” of their geometric structures [Figure 2A-D]^[30-32].

At the level of electronic structure and local microenvironment, the water-resistance advantage of single atoms further stems from their ability to finely regulate adsorption priority and reaction pathways. Single atoms are typically highly coordinated to oxides, carbon-based, or zeolite frameworks in the form of M-O, M-N, etc., and this coordination-induced strong charge transfer can significantly reshape the local electronic structure of the metal center. By regulating the electron cloud density of the isolated sites, the strong chemisorption of polar water molecules at such low-coordination sites can be effectively weakened, while retaining the activation ability towards target VOCs and oxygen. More significantly, specific metastable coordination structures can proactively alter the evolution pathway of water from a thermodynamic perspective [Figure 2E-H]^[33]. For instance, in some meticulously designed metastable single-atom (e.g., Pt₁/TiO₂) systems, the special local structure not only enhances lattice oxygen mobility to safeguard the smooth operation of the MvK mechanism but also transforms the dissociation process of H₂O from an endothermic reaction to an exothermic reaction, thereby facilitating the in situ dissociation of water into the highly active -OH*^[34].

In long-term service environments with high humidity and high temperatures, catalysts are highly prone to hydrothermally induced active-phase reconstruction and agglomeration or sintering. Numerous studies have indicated that precisely confining precious metal single atoms within lattice defects (e.g., abundant oxygen vacancies) of the support not only forms robust M–O bonding, but this SMSI also kinetically increases the migration energy barrier of metal atoms and effectively weakens the adsorption of H₂O at the metal active sites^[35]. Furthermore, encapsulating single atoms within the micropores of zeolites (e.g., silicalite-1 zeolite) with specific topology or constructing core-shell structures with microscopic physical barriers using ultrathin silica shells (e.g., constructing Pt-O-Si active interfaces) can generate a strong synergy with the confinement microenvironment of the support^[36,37]. This dual protection mechanism of chemical anchoring and physical confinement induces a favorable redistribution of the interfacial electronic structure, optimizes surface acidity, and promotes gas-phase oxygen activation. Consequently, it achieves exceptional stability and ensures that the active sites are atomically dispersed even under harsh conditions, such as high water vapor concentrations (> 10 vol%) and severe hydrothermal aging^[38].

Despite the rapid development of SACs in recent years, metal nanoparticles, by virtue of their high-density surface active sites, outstanding substrate activation capabilities, and mature loading processes, remain the most widely applied active phase system in the field of catalytic VOC oxidation at present^[39]. Therefore, a primary focus in designing water-resistant nanoparticle systems is identifying the optimal size window that balances substrate activation kinetics with hydrothermal stability^[40].

Aside from particle size, MSI is the focal point determining the water-resistant behavior of nanoparticles. The catalytic oxidation of VOCs typically does not occur independently on a pure metal surface but relies heavily upon the synergistic microenvironment at the junction between the metal and the support. Under humid conditions, interfacial charge transfer can significantly change the electron density of the noble metal surface [Figure 3]^[41]. By precisely regulating the interfacial electronic structure (for instance, constructing MnO_x/Pt heterojunctions^[42], selectively loading Ru on the SnO₂/CeO₂ mixed oxide surface^[43], or constructing Pt-WO₃ active interfaces), strong electronic coupling interactions can be induced at the interfaces^[44]. This reconfiguration of electron arrangements can effectively weaken the stable adsorption of polar water at the active sites while maintaining efficient activation of oxygen and VOC molecules. Furthermore, excellent interfaces often possess powerful oxygen migration and oxygen vacancy regeneration capabilities. When water molecules inevitably occupy part of the interfacial sites, the support, which is rich in oxygen vacancies, can continuously provide lattice oxygen or highly active oxygen species for the reaction via the rapid oxygen migration from the subsurface or interface, thereby effectively compensating for the damaged MvK oxygen cycle path due to the physical blocking by water molecules^[45].

Under long-term humid and hot service conditions, SMSI and spatial confinements constitute the final line of defense for nanoparticle systems against “hydrothermal reconstruction and sintering”. A high-humidity environment can accelerate the migration of active metals, giving rise to the permanent loss of low-coordination high-activity sites. To overcome this fatal flaw, researchers “anchor” nanoparticles by constructing physical confinement structures or strengthening chemical bonding. For example, using mesoporous zeolite shells to physically encapsulate the Pt-CeO₂ active components, this porous network not only plays a role in steric hindrance and hydrophobic buffering for water molecules but also tightly confines them within microscale channels, fundamentally suppressing Pt particle sintering induced by high-temperature water vapor and endowing the material with excellent hydrothermal stability^[27,46]. In addition, modifying supports (e.g., Al₂O₃) by introducing heteroatoms like Si can significantly enhance the thermal stability of the carrier and strengthen the interaction between the noble metal and the carrier, effectively maintaining the high dispersion and water resistance of the nanoparticles^[47]. However, interfacial regulation similarly needs to follow the classic Sabatier rule. Therefore, seeking a delicate balance between the site exposure rate and the interfacial anchoring strength is key to maximizing the water resistance of the metal nanoparticles.

In single-metal or single-metal oxide systems, because active sites are uniform, catalysts often struggle to simultaneously achieve high intrinsic activity and excellent water-resistant stability under humid working conditions. Competitive adsorption, hydroxyl accumulation, and structural degradation triggered by polar water molecules significantly amplify the intrinsic shortcomings of single-metal catalysts. To this end, introducing heterogeneous doping elements or constructing bi- or multi-metallic synergistic systems has become a key strategy for reshaping the surface reaction ecology at the atomic and molecular scales and enhancing the overall toughness of the catalytic network^[48].

First, electronic-structure reconstruction and differential adsorption regulation are the most fundamental microscopic mechanisms of the bimetallic strategy. Due to differences in electronegativity, valence state, and orbital energy levels between heterogeneous metals, strong local charge transfer is inevitably triggered at the interface or within the alloy phase. This redistribution of the local electron cloud can precisely shift the d-band center of the active metal, fundamentally changing the affinity of surface sites for different adsorbed species [Figure 4]^[23]. Under hot and humid working conditions, rational electronic regulation can effectively weaken the coordination bond strength between polar water and the active center, reducing the probability of deep dissociation of water and the formation of continuous hydroxyl networks. For example, by introducing specific heterogeneous metals around the active metal (e.g., constructing multi-element coupling structures)^[49,50], it is possible not only to inhibit the full coverage of active sites by water molecules but also to alter the adsorption configuration of water via directional electron transfer. While ensuring the preferential adsorption of VOCs and oxygen, this imparts an extremely high selective tolerance towards water molecules on the catalyst surface^[51].

Second, dynamic defect engineering and oxygen cycle compensation are core to maintaining reaction continuity in the presence of moisture. In the process of VOC oxidation following the MvK mechanism, water vapor directly cuts off the supply chain of lattice oxygen by strongly occupying the surface oxygen vacancies. Metal doping (such as introducing heterogeneous cations with ionic radii or valence state mismatch into transition metal oxides^[22,52], and even alkali metal ions like Na^+[53-57], K^+[58,59], or rare earth ions like Y^+[60], etc.) can induce strong microscopic distortion within the lattice, thereby directionally generating defect sites in large quantities [Figure 5A and B]^[49,54]. These customized defects not only substantially promote oxygen mobility within the lattice but also open up low-barrier activation channels for gaseous oxygen that are independent of water molecules. We emphasize that heavier alkali metals can tune the electronic environment of neighboring noble-metal sites, influence surface basicity and oxygen activation pathways, modify adsorption/desorption behavior of water and aromatic pollutants, in some cases, facilitate deep oxidation of molecules such as toluene under high-humidity conditions when combined with suitable noble-metal/transition-metal interfaces. At the same time, we note that the beneficial effect depends strongly on loading amount, dispersion, and interfacial structure, and excessive alkali addition may also suppress activity.

Finally, the decoupling of surface reaction paths and functional division effectively breaks through the catalytic limits of single sites. In complex humid systems, if multiple tasks (e.g., adsorbing substrates, dissociating oxygen molecules, and scavenging surface hydroxyls) are highly concentrated at the same active center, it easily gives rise to stagnation of the catalytic cycle due to competitive adsorption. Bimetallic or multi-component synergistic systems achieve perfect “division of labor and collaboration” through decoupling in spatial and chemical functions. For example, one metal component is responsible for preferentially capturing and activating VOC molecules with substantial steric hindrance, while the adjacent metal component serves as a “sacrificial site” or an oxygen supply hub, specifically responsible for accommodating water or accelerating the formation of active oxygen species [Figure 5C-F]^[61,62]. More interestingly, an appropriate amount of heterogeneous doping can even alter the action path of water, prompting interaction between adsorbed water and doped sites that convert into the highly active -OH species, which in turn assist in deeply tearing the C–C bonds of intermediate products (e.g., formates and acetates)^[63]. This synergistic strategy not only mitigates water film formation via geometric dilution but also converts water from a reaction poison into co-catalytic species that facilitate VOC oxidation^[64].

In supported catalyst systems, metal oxide supports have been frequently regarded as “inert platforms” for dispersing active components. Under humid working conditions, however, it is often the support surface that first comes into large-area contact and undergoes a strong interaction with water molecules^[65].

Firstly, interfacial hydrophobic modification and thermodynamic repulsion effects constitute the first physical barrier blocking moisture intrusion^[66-68]. By grafting inorganic siloxanes^[69], introducing fluorine-containing ligands^[70], or coating with low-surface-energy substances^[71] (e.g., N-doped carbon^[67]) on the metal oxide surface, the solid-liquid-gas three-phase contact angle can be effectively regulated, strictly limiting the enrichment of water clusters and capillary condensation at the interface on a spatial scale^[66,72] [Figure 6]^[67]. The introduction of such superhydrophobic coatings or hydrophobic ligands thermodynamically constructs a hydrophobic (VOCs-preferential) differentiated partition microenvironment. The catalyst can not only maintain high intrinsic activation capability but also induce the interaction between gaseous oxygen and residual water molecules to generate additional active oxygen (e.g., *OOH and *OH) species, thereby suppressing water-induced blockage while compensating for lattice oxygen consumption^[73,74].

Second, the reconstruction of surface acid-base properties and the inhibition of hydroxylation are the key to regulating water adsorption behaviors at the chemical bond level. The adsorption and deep dissociation of water molecules on oxide surfaces depend strongly on surface Lewis or Brønsted acid sites and strongly polar basic oxygen sites. If an excessive number of high-strength polar sites exist on the support surface, it easily induces the irreversible chemisorption of water, gradually developing into a dense surface hydroxyl layer^[75-77]. Through rational heterogeneous element doping^[78,79] (such as introducing specific non-metallic elements to replace surface hydroxyls) or constructing multi-component composite oxides^[80], the local charge distribution can be effectively adjusted to placate the extreme acid-base potential of the support surface. The goal of this acid-base microenvironment optimization is not to absolutely eliminate the acid sites but to establish a more moderate adsorption balance, i.e., to ensure efficient capture of VOC molecules with specific functional groups while kinetically greatly increasing the energy barrier for water molecule dissociation to form stable hydroxyls, maintaining water molecules in a weakly adsorbed state that is easy to desorb^[81].

Finally, strengthening lattice oxygen migration and the underlying compensation of the MvK mechanism are the core kinetic guarantees for maintaining high-humidity reaction continuity^[82-86]. Most metal oxides catalyze VOC oxidation according to the MvK mechanism, and the most detrimental effect of moisture is cutting off the cycle channel for gas-phase oxygen activation and lattice-oxygen replenishment through hydroxyl coverage. To break through this limitation, designing composite supports (e.g., solid solutions like Ce-Ti^[87], Cu-Mn^[88], Cu-Co^[89] or interfacial structures^[90,91]) to induce strong lattice distortion can endow the support with an extremely strong oxygen storage capacity and excellent bulk oxygen mobility^[21]. When water molecules inevitably mask part of the surface active sites, this type of modified support can act as an efficient lattice oxygen reservoir. It continuously delivers the highly active lattice oxygen and surface oxygen species to the active reaction interface through rapid oxygen transport from the bulk or subsurface^[91]. Meanwhile, precisely constructed oxygen vacancies can not only promote O₂ activation but also suppress H₂O adsorption through the charge transfer effect^[92]. This enables the support to favorably modulate the competitive equilibrium between moisture adsorption and active oxygen replenishment.

In heterogeneous catalytic systems, the water-resistance performance of the catalysts depends not only on their macroscopic chemical compositions but also, at a deeper level, is controlled by the spatial arrangement of surface atoms. A large number of studies have demonstrated that even under the premise of identical chemical composition and overall defect concentration, differences in the primary exposed crystal planes of the support or transitions in the crystal phase can lead to poles apart in activity retention under humid working conditions^[93].

Firstly, tailoring the surface coordination environment and reshaping intrinsic polarity are the most direct pathways by which crystal facet regulation influences water adsorption thermodynamics. Different crystal facets expose distinctly different metal/oxygen atom ratios, geometric configurations, and low-coordination states of surface atoms. These atomic-level geometric discrepancies directly translate into significant changes in surface free energy and local charge distribution. Using directional synthesis techniques to selectively expose specific crystal facets, the intrinsic polarity and hydrophilic/hydrophobic tendencies of the catalyst surface can be fundamentally altered^[60,94]. For example, certain specific facets can widen the formation distance of the hydrogen bond network among water molecules through special atomic spacing, hence blocking the spreading of a dense water film at the molecular scale^[95,96]. Meanwhile, the tailored local coordination environment can precisely weaken the binding energy between polar water molecules and surface sites, reversing the competitive adsorption disadvantage of H₂O against specific organic substrates (e.g., VOCs) at the thermodynamic level.

Secondly, the dynamic regeneration of active hydroxyl groups and the optimization of intermediate evolutionary pathways elucidate the promotional kinetic effect of moisture on specific crystal facets. Water molecules do not strictly function as the inhibitory species. On facets featuring step sites or specialized metal-support interfacial topology, the activation of water can be effectively harnessed to facilitate the reaction^[97]. For example, under the synergistic action of a specific proportion of oxidized metals and step sites, the moderate water dissociation can avoid the formation of a passivation layer while continuously and dynamically regenerating the highly active surface hydroxyl species (e.g., the highly active metal-OH)^[98]. These in situ generated hydroxyls not only compensate for the interfacial oxygen deficiency induced by moisture but also serve as key mediators of proton or electron transfer. This facilitates surface migration and oxidative cleavage of reaction intermediates (e.g., conversion of spectator formates to the active carboxylates) on the catalyst surface. By leveraging the topological characteristics of specific crystal facets, this mechanism successfully redefines the role of water molecules, shifting them from competitive inhibitors to kinetic promoters that accelerate the intermediate evolution.

The introduction of porous confined structures (e.g., MOFs) and their derivatives provides a dimension of mass transfer and local microenvironment regulation for enhancing the water resistance of catalytic systems^[99].

Firstly, pore confinement effects and precise sieving of molecular diffusion pathways constitute the preceding physical barrier to blocking moisture intrusion. In non-porous or macroporous systems, moisture-induced deactivation often initiates even before the surface reaction occurs, for instance, by preferentially occupying pore mouths, blocking internal diffusion paths, and locally forming dense hydrogen bond networks^[100]. By constructing sub-nanometer or nanometer-scale confined spaces with specific geometric sizes and topological morphologies, porous structures can rearrange the diffusion kinetic competition between H₂O and macromolecular VOCs at the molecular scale^[36,101,102]. This spatial confinement not only restricts the free assembly of bulky water clusters through physical steric hindrance but also forces water molecules and VOCs to undergo staggered-peak or diverted diffusion through directional transport in nanosized pores, greatly reducing the local concentration of H₂O around the active sites.

Secondly, customizing pore-wall chemical properties and reshaping the local hydrophobic microenvironment strip water of its competitive advantage at the thermodynamic level. Whether in pristine MOF materials or their derivative structures, highly hydrophobic “microclimate zones” can be constructed on the inner pore walls through ligand modification or retention of carbon/heteroatoms during the derivation process [Figure 7A and B]^[103,104]. This hydrophobization within the confined space is not a simple surface coating but rather completely disrupts the tendency of water to form local hydrogen bond networks through dense non-polar groups or local electric fields on the pore walls. When reactant molecules penetrate this microenvironment layer, the hydrophobic pore walls exert a strong affinity and enrichment effect on non-polar or weakly polar VOC molecules, while thermodynamically repelling water molecules outside the core reaction zone, causing water to lose most of its competitive advantage before approaching the actual catalytic interface.

Finally, the topological inheritance and multi-center synergy of MOF derivatives endow the catalysts with multi-dimensional repair capabilities under hot and humid working conditions. To address the limitations of MOF-derived materials in terms of high-temperature thermal stability and water resistance, the incorporation of heterometals can significantly enhance the redox stability of the framework and the structural integrity of the derived oxide skeleton [Figure 7C and D]^[105]. Meanwhile, constructing MOF-carbonaceous/oxide composite systems can simultaneously build hydrophobic barriers and reinforce mechanical properties. Using MOFs as precursors for thermal or non-thermal derivation allows for inheriting their highly regular porous skeletons and in situ generating atomically dispersed heterogeneous metals (e.g., multimetallic alloyed nanoclusters^[106] or metal oxides with high defect states^[107,108]) within the confined space. This derivation not only overcomes the weak temperature resistance of pristine MOFs but also effectively prohibits water vapor-induced sintering and agglomeration of active components via the strong metal-framework interactions and local confinement. More interestingly, in specific multimetallic derivative frameworks (e.g., transition metal and alkali metal synergistic systems), a moderate amount of moisture intruding into the pores, rather than giving rise to poisoning, can instead be activated by the specific sites and converted into reaction auxiliaries promoting the deep mineralization and tearing of VOCs (e.g., toluene)^[109-112].

In traditional thermal catalysis, the core issue underlying moisture inhibition lies in the strong bonding between polar water/hydroxyl species and active sites at low temperatures. Introducing a light field (ultraviolet, visible, or near-infrared light) not only expands the dimension of energy input but also fundamentally reshapes surface reaction kinetics through the photogenerated charge carriers or local thermal effects^[113-116].

In addition to introducing a light field, utilizing ozone (O₃) to replace or assist conventional O₂ is another potent “proactive regulation” water-resistance strategy. Conventional thermocatalysis is highly prone to catalyst deactivation by moisture, largely because water molecules poison the catalyst’s electron-donor sites, hindering the dissociative activation of background O₂. O₃, as a high-energy-state oxidant, has an extremely low decomposition activation energy barrier on the catalyst surface, fundamentally circumventing the traditional high-energy barrier of oxygen activation steps^[121-123]. In catalytic ozonation systems, the involvement of water molecules is no longer limited to simple competitive adsorption. Water can undergo strong coupling with primary oxygen species generated from O₃ decomposition, promoting the formation of a more reactive cascade of reactive oxygen species (ROS) radical network^[124-126]. This mechanism perfectly transforms the role of water molecules from a “poisoning site-occupier” into a “promoter of radical chain reactions”, achieving a fundamental leap in water-resistance performance^[127,128].

Although thermal, photothermal, and O₃-assisted catalysis have each shown good potential for VOC removal under humid conditions, their synergistic integration has been rarely explored. In particular, the combined use of light and O₃ may further improve low-temperature catalytic activity and water tolerance, but several challenges remain, including (i) the mismatch between photogenerated charge transfer and O₃ activation kinetics; (ii) excessive nonselective radical generation; (iii) catalyst over-oxidation or instability under simultaneous light and O₃ exposure; and (iv) the difficulty of simultaneously regulating water adsorption, O₃ activation, and VOC oxidation at the same interface. To overcome these limitations, future studies should focus on rational interfacial design, such as heterojunctions or defect-engineered interfaces for efficient charge separation, dual-functional active sites for selective O₃ activation and rapid hydroxyl removal, hydrophobic-reactive surfaces to suppress water accumulation, and plasmonic or photothermal structures to accelerate the desorption of water and intermediates.