b S Supporting InformationT he porous materials with extraordinarily high surface area have attracted enormous scientific attention due to their diverse potential applications in separation, 1 heterogeneous catalysis, 2 and gas storage. 3 During the last few decades, the surge to develop such useful materials has led scientists to produce a number of novel porous materials such as metal organic frameworks (MOFs), 4 covalent organic frameworks (COFs), 5 porous organic cages, 6 and microporous organic polymers (MOPs), 7 in addition to traditional porous materials such as zeolites and activated carbon etc. Among these porous materials, MOPs have attracted a particular attention due to their unique properties such as large surface area, low skeletal density and high chemical stability. "Davankov resins", that is, styrenetype polymers hypercrosslinked by FriedelÀCrafts reaction, 8 are one of the earliest types of MOPs and have been studied extensively, coming into industrial practice at the end of 1990s, however, the releasing hydrogen halide as byproduct is detrimental and hard to tackle. 3d,9 Hyper-cross-linked polypyrrole or polyaminobenzene or aminobenzene represent another kind of pioneering MOPs. 10 These two synthesis method can only be adapted to very limited monomers. Very recently, various other new kinds of MOPs have been developed, based on several types of reaction, such as polymers of intrinsic microporosity (PIMs) with dioxane unit, 3b microporous polymers such as conjugated microporous polymers (CMPs) 11 and porous aromatic frameworks (PAFs) 12 by various cross-coupling reactions of aromatic compound. MOPs were also formed by trimerizations of ethynyl 13 or nitrile groups, 14 by amide or imide or imine formation, 15 and via "click" chemistry. 16 All of these approaches have aimed to develop new microporous organic materials with higher surface areas and controlled pore sizes and functions. However, the transition metal catalysts or noble metal catalysts used for synthesis of CMPs, PAFs, and some other MOPs are expensive and rare. It is often also complicated to synthesize the monomers which must bear halogen, 11a ethynyl 17 or stereocontrolled structures such as spirocyclic monomers 17,18 used in MOPs. Hence, the sustainable mass production of MOPs is an unanswered challenge.In this report, we propose a new strategy, which involves "knitting" rigid building blocks with an external cross-linker. We used a simple one-step FriedelÀCrafts reaction of a low-cost cross-linker with ordinary, low functionality aromatic compounds to produce cost-effective microporous polymers with very high surface areas and the only byproduct was methanol. In this one-step cross-linking approach, formaldehyde dimethyl acetal (FDA) was used as an external cross-linker to react with various aromatic monomers (Scheme 1, parts aÀc). Typically, the monomer (e.g., benzene, 0.02 mol, 1.56 g), cross-linker (FDA, 0.06 mol, 4.56 g) and the catalyst (FeCl 3 , 0.06 mol, 9.75 g) were dissolved in 1,2-dichloroethane (DCE, 20 mL) and heate...
