The Crystalline Porous Polymeric materials (CPPs) also well known as Covalent Organic Frameworks (COFs) have concerned substantial research interest because of their extensive applications in molecular storage and separation, catalysis, sensing, opto-electronics etc. [1]. The overall properties and real time employments of such materials not only rely on the compositions but also their nano-scale morphology which plays an incredible role [2]. Therefore, an explicit understanding of the morphology-modulation with respect to their constituents is really demanding. This study accounted a detailed molecular level investigation on morphological evaluation in COFs emanates entirely from its primary building units. Here two new highly crystalline, permanently porous imine linked based COFs named 2,3-DhaTta (Surface area 1700 m2/g) and 2,3-DhaTab (Surface area 413 m2/g) was solvothermally synthesised by faintly varying linker core while retaining all other external factors unchanged. These COFs are found to self template into diverge morphologies including ribbons (2,3-DhaTta) and hollow spheres (2,3-DhaTab). Their mechanisms of formation have been thoroughly and systematically investigated where hollow sphere formation in this case was guided by inside out Ostwald Ripening phenomenon. Moreover, based on DFT (Density Functional Theory) study a significant correlation between stacking energy of two adjacent COF layers with their backbone planarity was established which was believed to be the predominant guiding factor for governing their crystallinity, porosity and morphological diversity evaluation [3].

The present work effectively highlights the utilization of Dynamic Covalent Chemistry (DCC) principles in conjunction with the keto–enol tautomerism to synthesize useful, stable, crystalline and porous Covalent Organic Frameworks (COFs) in water, which thereby merits over the conventional solvothermal COF synthesis protocol with its simpler and greener appeal.

Tw on ew chemically stable triazine-and phenylcore-based crystalline porous polymers (CPPs) have been synthesized using as ingle-step template-free solvothermal route.U nique morphological diversities were observed for these CPPs [2,3-DhaTta (ribbon) and 2,3-DhaTab (hollow sphere)] by simply altering the linker planarity.Adetailed time-dependent study established as ignificant correlation between the molecular level structures of building blocks with the morphology of CPPs.M oreover,aDFT study was done for calculating the interlayer stacking energy,w hich revealed that the extent of stacking efficiency is responsible for governing the morphological diversity in these CPPs.Twodimensionalcrystallineporouspolymers(CPPs),including covalent organic frameworks (COFs) [1] and covalent triazine frameworks (CTFs), [2] are porous materials constructed by covalently linked light elements,such as C, N, O, H, B, and Si. These materials have triggered substantial research interest because of their extensive applications in molecular storage, [3] catalysis, [4] sensing, [5] and opto-electronics.[6] However,the overall properties of such porous materials do not rely only on their composition, structure,and porosity, but also on their nanoscale morphologies.[7] Therefore,a n explicit understanding of the morphology-modulation with respect to their constituents is required.[8] To achieve such am olecular level understanding, herein we report two CPPs that self-assemble to ribbon and hollow spherical [9] morphologies upon crystallization in as ingle step without any templating agents.Hollow spherical structures are considered to be ah ighly important morphology in polymeric materials owing to several potential applications.H owever,t heir existence is extremely rare and often require the usage of templating agents.[10] Thei ntermediates responsible for producing these above morphologies were prepared at different time intervals to understand the mechanism for the formation of the final morphology (at 72 h).TheC PPs reported here show high crystallinity as revealed from their PXRD patterns (Figure 1). Ahigh intense peak at 2.88 8 (2q)f or 2,3-DhaTta and 2,3-DhaTab (Figure 1e and 1f,r espectively) appear owing to the strong reflections from the 100 planes.2,3-DhaTta and 2,3-DhaTab show other minor peaks at 4.9, 5.7, 7.5, and 9.98 8 (2q)o wing to the reflections from the 110, 200, 120, and 220 planes,r espectively.P eaks at 268 8 (2,3-DhaTta) and 25.88 8 (2,3-DhaTab) correspond to their 001 plane reflections.T he d-spacing values between the 001 planes were used to calculate the p-p stacking distances between vertically stacked CPP layers [3.3 and 3.4 inthe respected CPPs].The high crystallinity of these CPPs is attributed to the presence of strong intramolecular OÀH···N hydrogen bonding [11] interactions between the imine nitrogen and the hydroxy functionality of the aldehyde core,w hich is influential in keeping the phenyl rings in one plane and increases stacking interactions within adjacent CPP layers.T og et an overview...

Covalent organic frameworks (COFs) are a new family of novel 2D materials which are highly sought after for integration into future sensors and other devices for their highly porous structures and large surface areas.