……，以……: so as to, in order to (written purpose)
【高123】复句 / complex sentences (目的)
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
……，以 + verb: a second clause that begins with 以 gives the purpose of the action in the first, with the same subject: "in order to", "so as to". 政府用他们的名字命名这条街，以纪念在战争中牺牲的战士.
The verb after 以 is nearly always a two-syllable verb of intention or of the result aimed at: 纪念, 激励, 证明, 说明, 保证, 调动. A verb is required: ✗ 以学生积极.
The purpose comes after the action, whereas 为了 (hsk3-g17) usually stands at the head of the sentence (为了纪念……，政府……). 以 is neutral; 以便 (hsk6-g22) stresses convenience ("so that it is easier"), 以免 (hsk5-g05) the harm to be avoided. Written register: in speech you say 为了, or simply string the two actions together.
Examples
他每天早起跑步，以保持良好的身体状态。
Tā měitiān zǎoqǐ pǎobù, yǐ bǎochí liánghǎo de shēntǐ zhuàngtài.He gets up early to run every day, so as to keep in good shape.
学校增加了图书馆的开放时间，以满足学生的需要。
Xuéxiào zēngjiā le túshūguǎn de kāifàng shíjiān, yǐ mǎnzú xuésheng de xūyào.The school has extended the library's opening hours, to meet the students' needs.
原告提交了一百多页聊天记录，以证明她长期在下班后加班。
Yuángào tíjiāo le yì bǎi duō yè liáotiān jìlù, yǐ zhèngmíng tā chángqī zài xiàbān hòu jiābān.The plaintiff submitted over a hundred pages of chat records, to show that she had long worked overtime after hours.
公司制定了严格的管理制度，以保证员工和财物的安全。
Gōngsī zhìdìng le yángé de guǎnlǐ zhìdù, yǐ bǎozhèng yuángōng hé cáiwù de ānquán.The company has drawn up strict rules, to guarantee the safety of staff and property.
老师采用新的教学方法上课，以调动学生的积极性。
Lǎoshī cǎiyòng xīn de jiàoxué fāngfǎ shàngkè, yǐ diàodòng xuésheng de jījíxìng.The teacher uses a new teaching method in class, to get the students more involved.
政府用他们的名字命名这条街，以纪念在战争中牺牲的战士。
Zhèngfǔ yòng tāmen de míngzi mìngmíng zhè tiáo jiē, yǐ jìniàn zài zhànzhēng zhōng xīshēng de zhànshì.The government named this street after them, to commemorate the soldiers who died in the war.
Common mistakes
✗ ……，以为了纪念…… → ✓ ……，以纪念…… (no 为了 after 以).
✗ 老师上课，以学生积极。 → ✓ 老师上课，以调动学生的积极性。 (a verb is required after 以).
✗ 我去超市，以买点水果。 → ✓ 我去超市是为了买点水果。 (in daily speech use 为了; 以 stays a written word).