Novel host plant use by a specialist insect depends on geographic variation in both the host and herbivore species.

Understanding the circumstances under which insect herbivores will adopt a novel host plant is a longstanding question in basic and applied ecology. While geographic variation in host use can arise through differences in both herbivore preference and plant characteristics, there is a tendency to attribute geographic variation in host use to regional differences in herbivore preference alone. This is especially true for herbivores specialized to one or a few plant species. We compared how geographic variation in herbivore preference and host plant origin shape regional differences in host plant use by the specialized herbivore, Euphydryas phaeton. In parts of its range, E. phaeton uses only a native host, Chelone glabra, while in others, it also uses an introduced host, Plantago lanceolata. We offered female butterflies from each region the non-native host plant sourced from both regions and compared their oviposition behavior. The non-native host was almost universally rejected by butterflies in the region where only the native plant is used. In the region where butterflies use both hosts, females accepted non-native plants from their natal region twice as often as non-native plants from the other region where they are not used. Acceptance differed substantially among individual butterflies within regions but not among plants within regions. Thus, both individual preference and regional differences in both the insect and non-native host contributed to the geographic variation in different ways. These results highlight that, in addition to herbivore preference, regional differences in perceived plant suitability may be an important driver of diet breadth.

Thermal resistance effect on anomalous diffusion of molecules under confinement.

Diffusion is generally faster at higher temperatures. Here, a counterintuitive behavior is observed in that the movement of long-chain molecules slows as the temperature increases under confinement. This report confirms that this anomalous diffusion is caused by the "thermal resistance effect," in which the diffusion resistance of linear-chain molecules is equivalent to that with branched-chain configurations at high temperature. It then restrains the molecular transportation in the nanoscale channels, as further confirmed by zero length column experiments. This work enriches our understanding of the anomalous diffusion family and provides fundamental insights into the mechanism inside confined systems.

Spectroscopically Visualizing the Evolution of Hydrogen-Bonding Interactions.

Understanding chemical bond variations is the soul of chemistry as it is essential for any chemical process. The evolution of hydrogen bonds is one of the most fundamental and emblematic events during proton transfer; however, its experimental visualization remains a formidable challenge because of the transient timescales. Herein, by subtly regulating the proton-donating ability of distinct proton donors (zeolites or tungstophosphoric acid), a series of different hydrogen-bonding configurations were precisely manipulated. Then, an advanced two-dimensional (2D) heteronuclear correlation nuclear magnetic resonance (NMR) spectroscopic technique was utilized to simultaneously monitor the electronic properties of proton donors and acceptors (2-13C-acetone or trimethylphosphine oxide) through chemical shifts. Parabolic 1H-13C NMR relationships combined with single-well and double-well potential energy surfaces derived from theoretical simulations quantitatively identified the hydrogen bond types and allowed the evolution of hydrogen bonds to be visualized in diverse acid-base interaction complexes during proton transfer. Our findings provide a new perspective to reveal the nature and evolution of hydrogen bonds and confirm the superiority of 2D NMR techniques in identifying the subtle distinctions of various hydrogen-bonding configurations.

Carbocation chemistry confined in zeolites: spectroscopic and theoretical characterizations.

Acid-catalyzed reactions inside zeolites are one type of broadly applied industrial reactions, where carbocations are the most common intermediates of these reaction processes, including methanol to olefins, alkene/aromatic alkylation, and hydrocarbon cracking/isomerization. The fundamental research on these acid-catalyzed reactions is focused on the stability, evolution, and lifetime of carbocations under the zeolite confinement effect, which greatly affects the efficiency, selectivity and deactivation of zeolite catalysts. Therefore, a profound understanding of the carbocations confined in zeolites is not only beneficial to explain the reaction mechanism but also drive the design of new zeolite catalysts with ideal acidity and cages/channels. In this review, we provide both an in-depth understanding of the stabilization of carbocations by the pore confinement effect and summary of the advanced characterization methods to capture carbocations in zeolites, including UV-vis spectroscopy, solid-state NMR, fluorescence microscopy, IR spectroscopy and Raman spectroscopy. Also, we clarify the relationship between the activity and stability of carbocations in zeolite-catalyzed reactions, and further highlight the role of carbocations in various hydrocarbon conversion reactions inside zeolites with diverse frameworks and varying acidic properties.

Controlling Metal-Oxide Reducibility for Efficient C-H Bond Activation in Hydrocarbons.

Knowing the structure of catalytically active species/phases and providing methods for their purposeful generation are two prerequisites for the design of catalysts with desired performance. Herein, we introduce a simple method for precise preparation of supported/bulk catalysts. It utilizes the ability of metal oxides to dissolve and to simultaneously precipitate during their treatment in an aqueous ammonia solution. Applying this method for a conventional VOx -Al2 O3 catalyst, the concentration of coordinatively unsaturated Al sites was tuned simply by changing the pH value of the solution. These sites affect the strength of V-O-Al bonds of isolated VOx species and thus the reducibility of the latter. This method is also applicable for controlling the reducibility of bulk catalysts as demonstrated for a CeO2 -ZrO2 -Al2 O3 system. The application potential of the developed catalysts was confirmed in the oxidative dehydrogenation of ethylbenzene to styrene with CO2 and in the non-oxidative propane dehydrogenation to propene. Our approach is extendable to the preparation of any metal oxide catalysts dissolvable in an ammonia solution.

Evolutionary and ecological patterns of scatter- and larder-hoarding behaviours in rodents.

Scatter- and larder hoarding are the primary strategies of food-hoarding animals and have important implications for plant-animal interactions and plant recruitment. However, their origins and influencing factors have not been fully investigated across a wide range of taxa. Our systematic literature search amassed data for 183 seed-hoarding rodent species worldwide and tested relationships of seed-hoarding behaviours with phylogenetic signal, functional traits and environmental factors. We found that the evolution of hoarding strategies was not random in phylogeny, and scatter hoarding originated independently multiple times from larder hoarding. Rodents with higher encephalisation quotient (relative brain size), omnivorous diet (related to dependence on seeds) and inhabiting lower latitudes were disproportionately likely to scatter hoard. Despite body mass's potential relationship with competition through food defence, it was associated with food-hoarding strategy only in a few families. Our results show the need to study the community and ecological context of food-hoarding behaviours.

Coking-Resistant Polyethylene Upcycling Modulated by Zeolite Micropore Diffusion.

Although the mass production of synthetic plastics has transformed human lives, it has resulted in waste accumulation on the earth. Here, we report a low-temperature conversion of polyethylene into olefins. By mixing the polyethylene feed with rationally designed ZSM-5 zeolite nanosheets at 280 °C in flowing hydrogen as a carrier gas, light hydrocarbons (C1-C7) were produced with a yield of up to 74.6%, where 83.9% of these products were C3-C6 olefins with almost undetectable coke formation. The reaction proceeds in multiple steps, including polyethylene melting, flowing to access the zeolite surface, cracking on the zeolite surface, formation of intermediates to diffuse into the zeolite micropores, and cracking into small molecules in the zeolite micropores. The ZSM-5 zeolite nanosheets kinetically matched the cascade cracking steps on the zeolite external surface and within micropores by boosting the intermediate diffusion. This feature efficiently suppressed the intermediate accumulation on the zeolite surface to minimize coke formation. In addition, we found that hydrogen participation in the cracking process could hinder the formation of polycyclic species within zeolite micropores, which also contributes to the rapid molecule diffusion. The coking-resistant polyethylene upcycling process at a low temperature not only overturns the general viewpoint for facile coke formation in the catalytic cracking over the zeolites but also demonstrates how the polyethylene-based plastics can be upcycled to valuable chemicals. In addition to the model polyethylene, the reaction system worked efficiently for the depolymerization of multiple practically used polyethylene-rich plastics, enabling an industrially and economically viable path for dealing with plastic wastes.

Surface Fingerprinting of Faceted Metal Oxides and Porous Zeolite Catalysts by Probe-Assisted Solid-State NMR Approaches.

Acid catalysis in heterogeneous systems such as metal oxides and porous zeolites has been widely involved in various catalytic processes for chemical and petrochemical industries. In acid-catalyzed reactions, the performance (e.g., activity and selectivity) is closely associated with the acidic features of the catalysts, viz., type (Lewis vs Brønsted acidity), distribution (external vs internal surface), strength (strong vs weak), concentration (amount), and spatial interactions of acidic sites. The characterization of local structure and acidic properties of these active sites has important implications for understanding the reaction mechanism and the practical catalytic applications of acidic catalysts. Among diverse acidity characterization approaches, the solid-state nuclear magnetic resonance (SSNMR) technique with suitable probe molecules has been recognized as a reliable and versatile tool. Such a probe-assisted SSNMR approach could provide qualitative (type, distribution, and spatial interactions) and quantitative (strength and concentration) information on each acidic site. This Account aims to integrate our recent important findings in determining the structures and acidic characteristics of some typical metal oxide and zeolite catalysts by using the probe-assisted SSNMR technique, as well as clarifying the continuously evolving process of each discrete acidic site under hydrothermal or chemical treatments even at the molecular level with multiscale theoretical simulations.More specifically, we will describe herein the development and applications of the probe-assisted SSNMR methods, such as trimethylphosphine (TMP) and acetonitrile-d3 (CD3CN) in conjunction with advanced two-dimensional (2D) homo- and heteronuclear correlation spectroscopy, for characterizing the structures and properties of acidic sites in varied solid catalysts. Moreover, relevant information regarding the surface fingerprinting of various facets on crystalline metal oxide nanoparticles and active centers inside porous zeolites, the mapping of relevant spatial interactions, and the verification of structure-activity correlation were investigated as well. Relevant discussions are mainly based on the recent NMR experiments of our collaborating research groups, including (i) determining the acidic characterization with probe-assisted SSNMR approaches, (ii) mapping various active centers (or crystalline facets), and (iii) revealing their influence on catalytic performance of solid acid catalyst systems. It is anticipated that this information may provide more in-depth insights toward our fundamental understanding of solid acid catalysis.

Alteration of Gut Microbiota of a Food-Storing Hibernator, Siberian Chipmunk Tamias sibiricus.

Hibernation represents a state of fasting because hibernators cease eating in the torpid periods. Therefore, food deprivation during hibernation is expected to modify the gut microbiota of host. However, there are few reports of gut microbiota in food-storing hibernators that feed during the interbout arousals. Here we collected fecal samples of Siberian chipmunk T. sibiricus to character and examine changes in the gut microbiota at various stages relative to hibernation: pre-hibernation, early-hibernation, mid-hibernation, late-hibernation, and post-hibernation. Compared to the pre-hibernation state, alpha-diversity of gut microbiota was significantly increased during the interbout arousal periods. In addition, beta-diversity of the fecal communities from pre-hibernation and interbout arousal periods grouped together, and post-hibernation gut microbiota resembled the counterpart at late-hibernation. Hibernation significantly decreased the relative abundance of Firmicutes but increased Bacteroidetes, reflecting a shift of microbiota toward taxa in favor of host-derived substrates. The increased abundance of Ruminococcaceae_UCG-014, Lactobacillus, and Christensenellaceae_R-7_group in gut microbiota may help the chipmunks reduce intestinal inflammation and then maintain healthy bowel during hibernation. KEGG pathway indicated that hibernation altered the metabolic function of gut microflora of T. sibiricus. Our study provides evidence that the gut microbiota of food-storing hibernators, despite feeding during the interbout arousals, shows similar response to hibernation that has well documented in fat-storing counterparts, suggesting the potential for a core gut microbiota during hibernation of mammals. Importantly, these results will broaden our understanding of the effects of hibernation on gut microbiota of mammal hibernators.

Induced Active Sites by Adsorbate in Zeotype Materials.

There has been a long debate on how and where active sites are created for molecular adsorption and catalysis in zeolites, which underpin many important industrial applications. It is well accepted that Lewis acidic sites (LASs) and basic sites (LBSs) as active sites in pristine zeolites are generally believed to be the extra-framework Al species and residue anion (OH-) species formed at fixed crystallographic positions after their synthesis. However, the dynamic interactions of adsorbates/reactants with pristine zeotype materials to "create" sites during real conditions remain largely unexplored. Herein, direct experimental observation of the establishment of induced active sites in silicoaluminophosphate (SAPO) by an adsorbate is for the first time made, which contradicts the traditional view of the fixed active sites in zeotype materials. Evidence shows that an induced frustrated Lewis pair (FLP, three-coordinated framework Al as LAS and SiO (H) as LBS) can be transiently favored for heterolytic molecular binding/reactions of competitive polar adsorbates due to their ineffective orbital overlap in the rigid framework. High-resolution magic-angle-spinning solid-state NMR, synchrotron X-ray diffraction, neutron powder diffraction, in situ diffuse reflectance infrared Fourier transform spectroscopy, and ab initio molecular dynamics demonstrate the transformation of a typical Brønsted acid site (Al(OH)Si) in SAPO zeolites to new induced FLP structure for hetereolytic binding upon adsorption of a strong polar adsorbate. Our unprecedented finding opens up a new avenue to understanding the dynamic establishment of active sites for adsorption or chemical reactions under molecular bombardment of zeolitic structures.

Molecular Understanding of the Catalytic Consequence of Ketene Intermediates under Confinement.

Neutral ketene is a crucial intermediate during zeolite carbonylation reactions. In this work, the roles of ketene and its derivates (viz., acylium ion and surface acetyl) associated with direct C-C bond coupling during the carbonylation reaction have been theoretically investigated under realistic reaction conditions and further validated by synchrotron radiation X-ray diffraction (SR-XRD) and Fourier transformed infrared (FT-IR) studies. It has been demonstrated that the zeolite confinement effect has significant influence on the formation, stability, and further transformation of ketene. Thus, the evolution and the role of reactive and inhibitive intermediates depend strongly on the framework structure and pore architecture of the zeolite catalysts. Inside side pockets of mordenite (MOR), rapid protonation of ketene occurs to form a metastable acylium ion exclusively, which is favorable toward methyl acetate (MA) and acetic acid (AcOH) formation. By contrast, in 12MR channels of MOR, a relatively longer lifetime was observed for ketene, which tends to accelerate deactivation of zeolite due to coke formation by the dimerization of ketene and further dissociation to diene and alkyne. Thus, we resolve, for the first time, a long-standing debate regarding the genuine role of ketene in zeolite catalysis. It is a paradigm to demonstrate the confinement effect on the formation, fate, and catalytic consequence of the active intermediates in zeolite catalysis.

Inter-trophic Interaction of Gut Microbiota in a Tripartite System.

Gut microbiota can be transmitted either environmentally or socially and vertically at intraspecific level; however, whether gut microbiota interact along trophic levels has been largely overlooked. Here, we characterized the gut bacterial communities of weevil larvae of Curculio arakawai that infest acorns of Mongolian oak (Quercus mongolica) as well as acorn-eating mammals, Siberian chipmunk (Tamias sibiricus), to test whether consumption of seed-borne larvae remodels the gut bacterial communities of T. sibiricus. Ingestion of weevil larvae of C. arakawai significantly altered the gut bacterial communities of T. sibiricus. Consequently, T. sibiricus fed larvae of C. arakawai showed higher capability to counter the negative effects of tannins, in terms of body weight maintenance, acorn consumption, N content in feces, urine pH, and blood ALT activity. Our results may first show that seed-borne insects as hidden players have a potential to alter the gut microbiota of seed predators in the tripartite system.

Genome-wide identification of ABA receptor PYL/RCAR gene family and their response to cold stress in Medicago sativa L.

Abscisic acid (ABA) is an important phytohormone involved in plant growth, plant development, and the protection of plants against abiotic stresses. PYL/RCAR (pyrabactin resistance/pyr1-like/regulatory components of ABA receptor) is the receptor protein of ABA and the core component of the ABA signal transduction network. The PYL gene family has been identified and analyzed in many species, however, there is no report about the research on the whole genome-wide identification of the alfalfa (Medicago sativa L.) PYL gene family. Therefore, to explore the function of alfalfa PYL genes, 39 MsPYL genes were identified by analyzing the recently published genome of alfalfa. Using bioinformatics methods, we systematically analyzed the chromosome location, protein physicochemical properties, evolutionary relationship, conserved motifs, and response to low-temperature stress of the MsPYL family of alfalfa. The results showed that 39 alfalfa MsPYL genes were distributed on 24 chromosomes, and the analysis of gene duplication events showed that fragment duplication was predominant duplication in alfalfa MsPYL family gene expansion. The phylogenetic tree of MsPYL protein of alfalfa and the phylogenetic tree of PYL genes of 3 species show that the MsPYL gene family can be divided into 3 subfamilies, and the structures of the same subfamilies are relatively similar. The 39 MsPYL gene family members of alfalfa contain 10 Motifs. Motif1, Motif2, Motif3, and Motif5 are the conserved motifs shared by these genes; cis-regulatory elements in promoter regions indicate that regulatory elements related to transcription, cell cycle, development, hormone, and stress response are abundantly present in the MsPYL promoter sequences; Real-time fluorescence quantitative PCR analysis showed that the expression of MsPYL genes can be induced by low-temperature treatment. This study provides a reference for further exploring the structural and functional characterization of the alfalfa PYL gene family. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01066-3.

In Situ Observation of Non-Classical 2-Norbornyl Cation in Confined Zeolites at Ambient Temperature.

Carbonium ions are an important class of reaction intermediates, but their dynamic evolution is difficult to be monitored by in situ techniques under experimental conditions because of their extremely short lifetime. Probably the most famous case is 2-norbornyl cation (2NB+ ): its existing form (classical or non-classical) had been debated for decades, until the concrete proof of non-classical geometry was achieved by X-ray crystallographic characterization at ultra-low temperature (40 K) and super acidic environment. However, we lack the understanding about 2NB+ at ambient conditions. Herein, by taking advantage of the confinement effect and delocalized acidic environment of zeolites, we successfully stabilized 2NB+ and unequivocally confirmed its "non-classical" structure inside the ZSM-5 zeolite by ab initio molecular dynamics simulations and 13 C solid-state nuclear magnetic resonance experiments. It is the first time to in situ observe the non-classical 2NB+ without the super acidic environment at ambient temperature, which provides a new strategy to expand the carbocation chemistry.

Electronic-State Manipulation of Surface Titanium Activates Dephosphorylation Over TiO2 Near Room Temperature.

Dephosphorylation that removes a phosphate group from substrates is an important reaction for living organisms and environmental protection. Although CeO2 has been shown to catalyze this reaction, cerium is low in natural abundance and has a narrow global distribution (>90 % of these reserves are located within six countries). It is thus imperative to find another element/material with high worldwide abundance that can also efficiently extract the phosphate out of agricultural waste for phosphorus recycle. Using para-nitrophenyl phosphate (p-NPP) as a model compound, we demonstrate that TiO2 with a F-modified (001) surface can activate p-NPP dephosphorylation at temperatures as low as 40 °C. By probe-assisted nuclear magnetic resonance (NMR), it was revealed that the strong electron-withdrawing effect of fluorine makes Ti atoms (the active sites) on the (001) surface very acidic. The bidentate adsorption of p-NPP on this surface further promotes its subsequent activation with a barrier ≈20 kJ mol-1 lower than that of the pristine (001) and (101) surfaces, allowing the activation of this reaction near room temperature (from >80 °C).

Modulation of Self-Separating Molecular Catalysts for Highly Efficient Biomass Transformations.

The energetically viable fabrication of stable and highly efficient solid acid catalysts is one of the key steps in large-scale transformation processes of biomass resources. Herein, the covalent modification of the classical Dawson polyoxometalate (POMs) with sulfonic acids (-SO3 H) is reported by grafting sulfonic acid groups on the POM's surface followed by oxidation of (3-mercaptopropyl)trimethoxysilane. The acidity of TBA6 -P2 W17 -SO3 H (TBA=tetrabutyl ammonium) has been demonstrated by using 31 P NMR spectroscopy, clearly indicating the presence of strong Brønsted acid sites. The presence of TBA counterions renders the solid acid catalyst as a promising candidate for phase transfer catalytic processes. The TBA6 -P2 W17 -SO3 H shows remarkable activity and selectivity, excellent stability, and great substrate compatibility for the esterification of free fatty acids (FFA) with methanol and conversion into biodiesel at 70 °C with >98 % conversion of oleic acid in 20 min. The excellent catalytic performance can be attributed to the formation of a catalytically active emulsion, which results in a uniform catalytic behavior during the reaction, leading to efficient interaction between the substrate and the active sites of the catalyst. Most importantly, the catalyst can be easily recovered and reused without any loss of its catalytic activity owing to its excellent phase transfer properties. This work offers an efficient and cost-effective strategy for large-scale biomass conversion applications.

Origin and Structural Characteristics of Tri-coordinated Extra-framework Aluminum Species in Dealuminated Zeolites.

Post-synthetic dealumination treatment is a common tactic adopted to improve the catalytic performance of industrialized zeolitic catalysts through enhancements in acidity and stability. However, among the possible extra-framework aluminum (EFAL) species in dealuminated zeolites such as Al3+, Al(OH)2+, Al(OH)2+, AlO+, AlOOH, and Al(OH)3, the presence of tri-coordinated EFAL-Al3+ species, which exhibit large quadrupolar effect due to the lack of hydrogen-bonding species, was normally undetectable by conventional one- and two-dimensional 1H and/or 27Al solid-state nuclear magnetic resonance (SSNMR) techniques. By combining density functional theory (DFT) calculations with experimental 31P SSNMR using trimethylphosphine (TMP) as the probe molecule, we report herein a comprehensive study to certify the origin, fine structure, and possible location of tri-coordinated EFAL-Al3+ species in dealuminated HY zeolite. The spatial proximities and synergies between the Brønsted and various Lewis acid sites were clearly identified, and the origin for the observed EFAL-Al3+ species with ultra-strong Lewis acidity was deduced to be at the expense of adjacent Brønsted acid sites. The excellent performance of such tri-coordinated EFAL species was furthermore confirmed by glucose isomerization reactions.

Effects of tannins on population dynamics of sympatric seed-eating rodents: the potential role of gut tannin-degrading bacteria.

Chemical compounds in seeds exert negative and even lethal effects on seed-consuming animals. Tannin-degrading bacteria in the guts of small mammals have been associated with the ability to digest seeds high in tannins. At the population level, it is not known if tannins influence rodent species differently according to the composition of their gut microbiota. Here, we test the hypothesis that sympatric tree species with different tannins exert contrasting effects on population fluctuations of seed-eating rodents. We collected a 10-year dataset of seed crops and rodent population sizes and sequenced 16S rRNA of gut microbes. The abundance of Apodemus peninsulae was not correlated with seed crop of either high-tannin Quercus mongolica or low-tannin Corylus mandshurica, but positively correlated with their total seed crops. Abundance of Tamias sibiricus was negatively correlated with seed crop of Q. mongolica but positively correlated with C. mandshurica. Body masses of A. peninsulae and T. sibiricus decreased when given high-tannin food; however, only the survival of T. sibiricus was reduced. The abundance of microbial genus Lactobacillus exhibiting potential tannin-degrading activity was significantly higher in A. peninsulae than in T. sibiricus. Our results suggest that masting tree species with different tannin concentrations may differentially influence population fluctuations of seed predators hosting different gut microbial communities. Although the conclusion is based on just correlational analysis of a short time-series, seeds with different chemical composition may influence rodent populations differently. Future work should examine these questions further to understand the complex interactions among seeds, gut microbes, and animal populations.

Selective predation on acorn weevils by seed-caching Siberian chipmunk Tamias sibiricus in a tripartite interaction.

Although food-hoarding animals benefit plant seeds by generating predation pressure on granivorous insects, we lack experimental evidence of whether the tripartite interactions maintain a mutualistic relationship between the third trophic level and primary producers. Relying on the behavior of shelling, Siberian chipmunks (Tamias sibiricus) selectively consumed weevil larvae infested in acorns of Mongolian oak (Quercus mongolica) but chose the non-infested acorns to scatter-hoard. Shelling not only reduced volatile emission from acorns but also decreased cache loss to pilferers, weevil larvae and fungi, allowing T. sibiricus to gain more rewards from their caches. Moreover, shelling by T. sibiricus enhanced acorn germination and seedling establishment of Q. mongolica, possibly due to the diminishment of the negative effects of weevil infestation on acorn viability. Here, we show that both food-hoarding animal T. sibiricus and oak Q. mongolica can be conditionally benefited from selective predation on weevil larvae inside acorns. Our results highlight the need to integrate the mutualisms between the third and first trophic level into the tripartite interaction model. We suggest that more efforts should be made in the tripartite interactions of food-hoarding animals, seeds and granivorous insects.

Lithium doping on 2D squaraine-bridged covalent organic polymers for enhancing adsorption properties: a theoretical study.

Lithium modification, especially quantitative and oriented doping, is an effective way to enhance the adsorption properties of covalent organic frameworks (e.g., CO2 and H2). Two-dimensional squaraine-bridged covalent organic polymers (SQ-COPs), with quantitative and oriented Li-doped open oxygen sites of the squaric-acid unit, are investigated for their CO2 capture properties by using first-principles calculation combined with grand canonical Monte Carlo (GCMC) simulation. It is found that owing to the strong affinity of Li atoms to the squaraine units of SQ-COPs, the gas adsorption capacity in SQ-COP-Li increased to 3 times more than those of the pristine SQ-COPs. In particular, since the Li-O bonds between squaraine units and Li atoms can enhance the electrostatic interaction between the framework and CO2, the adsorption amount of CO2 in SQ-COP-Li reaches an extremely high capacity of 83.4 and 202.0 mmol g-1 at 298 K and 100 bar for 1-Li (SQ-COP-1-Li) and 3-Li (SQ-COP-3-Li), respectively. Such a high CO2 uptake means that 3-Li outperforms the best 3D COF (COF-05) materials so far reported, and is even twice that of MOF-177 and IRMOF-10. Even at 30 bar and 298 K, the CO2 uptake values of 49.2 mmol g-1 of 1-Li and 61.5 mmol g-1 of 3-Li are far higher than 29.7 mmol g-1 of Li-doped COF-102 and 42.0 mmol g-1 of Li-doped COF-105. Moreover, the selectivity of CO2/H2 and CO2/CH4 in 1-Li reaches 19 and 5.4 at 273 K, and 10.3 and 3.6 at 298 K, respectively. Therefore, such Li-doped SQ-COPs might be an environmentally friendly candidate for high CO2 capture. Furthermore, the possible synthesis pathways of SQ-COP-Li are investigated, and it is indicated that the use of lithium di-isopropylamide and lithium naphthalene as dopants is energetically favorable. The findings in this work are expected to provide new ideas for metal doping and extended applications of functionalized materials.